Practically Classics Forum

What is happening with the engine?

rich. wrote: Sat Jun 29, 2024 3:04 pm What is happening with the engine?

Have just been chasing up a couple of leads to see if they go anywhere. At the moment though it's just waiting patiently.

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Fallen behind a bit.

Somewhat idiotically, I didn't make sure that the Rover was drowned in wax before the winter. This was a mistake and made for a lot of scrubbing.



Likewise the Renault (which I do confess to having been kind of ignoring and hoping it will miraculously fix itself for a while - it hasn't) was even worse.





Couple of hours with the pressure washer and some scrubbing had things looking a bit more presentable.









Of course something fell off the Rover. Because Rover.





So had to glue that back on.



Which naturally meant I managed to get glue everywhere when the badge slipped out of my hands, because I'm a nightmare where anything involving adhesives is involved.


Driving the P6 through built up areas at low speeds with the windows down, the really deep burble just off idle definitely puts a grin on my face when it gets bounced back by surrounding buildings. It was quite pleasant to be driving it again.

Of course because it's this car we couldn't have a journey without something new cropping up. This time it was the temperature gauge which decided to go on strike.



Perfect on a hot day! That didn't add any anxiety to the drive home at all...no, I definitely wasn't at all worried...

Looks like we have an issue with the power supply to it as I'm only seeing 1.3V at the sensor. Which I promptly broke the terminal off.



New one added - which of course didn't fix the gauge.



Not that I really expected it to given the voltage reading. My guess is that the 5V regulator for the instrument panel (which I rebuilt using a solid state regulator) has died. Usually this would be made obvious by the fuel gauge also dying, but as that doesn't work anyway it's harder to be certain. Not going to have time to look into this today anyway.

Very exciting news to me though was that after having the enging idling for a couple of minutes while I fiddled with that was that I had no oil drips!



Coolant drips instead! Which appears to actually be coming from around this top radiator hose.



I have moved the hose clip a bit closer to the end of the hose, but given that end tank has obviously seen "some repair work" in the past, to be making sure there's not a crack or other damage to the hose mating surface which would cause us issues.

There is a tiny weep from a porous spot you can see in the photo, I think this drip is totally separate to that though.

Did get a nice photo while out though. Right up to the point I realised the bonnet wasn't fully latched.



Guess I'll need to snap that again then!

Which brings us to yesterday.

The instrument panel was once again pulled out of the car.



Which is actually really easy once you know how it comes apart. Less than ten minutes had the panel on the operating table. Any resemblance to our dining table is entirely coincidental.



One very important step was ensuring that the speedometer drive was securely sealed to ensure it didn't get grease everywhere.



A little more strip down then followed. I have to give the designers credit, this is by far the easiest instrument panel I've ever dismantled. Though there are some slightly questionable design decisions hidden within. These panels have a bit of a reputation for having connection issues. One source of these is some riveted vias through the PCBs, though I think I've found another obvious potential trouble spot. I give you the connection interface between what I have termed the backplane and the instrument sub assemblies.



Yes, that is just a hole in the solder mask where the PCB traces on the two boards are squeezed together by a nearby machine screw. While I'm sure this was a real boon in terms of production streamlining (the P6 I believe I read was actually the first mass produced car to use a PCB based instrument cluster, though I believe that was the original version, by the time this P6B was made plenty of others would have followed suit), 49 years and quite a bit of damp ingress later it sounds like a potential continuity nightmare.

The first specific bit of the panel I investigated was actually the ammeter. I had seen this twitch a few times but never really saw any significant deflection. More recently it had appeared to be completely dead. This turned out to be an entirely physical problem.

Here's a close up of the meter movement as it came out of the panel.



The issue is actually that the little circuit board on which the coil is mounted has over time and goodness knows how many heat cycles, worked itself loose. This has allowed it to drop downwards by about 1/8". This in turn meant that the armature of the meter had shifted too far away from the coil to be influenced by the magnetic field. This is actually where things should sit.



The board was originally held in place by the grommets around the spade terminals on the back, these however have lost their grip over the years. I eventually opted for just putting a couple of blobs of epoxy in strategic locations to hold it together.

I've always found the difference in designs of instrument panels of cars through the years always to be fascinating. So I was quite interested in a discovery I made while pulling the movement for the ammeter out. Warning...instrument panel design nerd rabbit hole ahead.

I had noted back when I first got this car that this instrument panel seemed to be extremely well and evenly illuminated for what I thought was an edge lit panel. Which based on being an early 70s design and having clearly raised digits it appeared to be.



Really is impressively well lit for something this old.



Turns out that it looks really evenly lit because it IS actually backlit. The edge lighting is purely for the pointers. Though not backlit in the way you're more used to seeing it executed. Turns out that the dial face itself is solid translucent turquoise tinted plastic with the black finish painted on. This is then clamped onto a solid 1/4" or so thick block of clear acrylic which is formed to behave as a light guide to provide an even illumination across the whole face. As demonstrated by me using a torch here.



This must have been really quite advanced panel design for the early 70s. Hats off to the designers - the night time illumination of this dash is easily as good as on any other car I've driven. Never mind one that was designed in the opening years of the 70s.

While the illumination might be quite high tech for the time, the actual gauge movements are pretty old school. These are all thermal gauge movements. If you've not seen one of these before, here's what's behind the face of one.



About as simple as it gets. It is literally a heater coil wound around a bimetallic strip. One end of this strip is rigidly mounted, the other is attached to the pivot of the meter needle. So as the current through the coil increases, the strip heats up more, it bends more and pushes the meter needle further. Very simple, and has the advantage of being inherently heavily damped. The downside is that they're obviously more power hungry than moving coil or moving iron meter movements.

Here ends the really nerdy bit, and we get back to fixing things.

The main fault I had dismantled things to address was the temperature gauge having decided to go on strike - I was pretty sure because the voltage regulator had died.

I had rebuilt the original thermal 10V regulator using a 7810 shortly after I got the car. However I really hadn't thought it through when I did this, specifically quite how electrically noisy an environment a car is. More specifically, it's also an environment where there are some really quite spicy transients floating around - especially when the starter motor solenoid is disconnected. As I learned much to my cost when I got an *almighty* belt off a Bedford YNT coach when fault finding an intermittent ignition switch. I don't know exactly what voltages or currents were involved, but that one was easily up there in the top five list for the most painful shocks I've had. The poor little 7810 really wasn't designed to deal with this sort of nonsense. There are proper transient protection diodes (I'm assuming they're basically very fast zener diodes) to install in settings like this. I don't have anything like that in stock, but I'll get some ordered for the future. For now I've added a 10uF bypass cap on the input side to hopefully help out - if I need to swap this again in future it's about 15-20 minutes work to get the regulator out and on the bench. You don't need to fully remove the dash from. The car, just pull it forward a bit so the regulator can be unplugged from the back.

The regulator shortly before it was crammed back together.



Before things went back together I also bridged the riveted connections to the regulator sockets with a bit of solder. It's not pretty, but it means the rivets aren't the sole things involved in making the electrical connection now.



Obviously I also gave all of the contact pads a really good clean. The scratches on some of these shows that I'm definitely not the first person to be in here.

The panel was thrown back together, lamp holders cleaned, speedometer drive greased, and inside of the front cover cleaned, then it was out back into the car. Result?



One working temperature gauge.

The ammeter is also now showing a lot more deflection than it was. Still sits pointing at a slight discharge as someone has clearly slightly bent the needles on both that and the oil pressure gauge slightly at some point. I'll need to fine tune that at some point but that's a job for future me.

Feeling accomplished here I decided to dig a bit further into the fuel gauge. I had tested the gauge itself in isolation and confirmed that it worked. I'm pretty sure that I had checked and found the sender itself to be open circuit from under the car. However I hadn't (as far as I could remember) really investigated the wiring to the back of the car. I had suspicions about it though - especially this chopped wire visible in the boot.



Sure enough testing this wire on the meter showed it to have 10V on it, and grounding it for a couple of seconds caused the fuel gauge to spring to life.



The wiring in the boot has suffered quite a lot of hackery in general from when the tow bar electrics were wired in (masking tape has good long term electrical insulation properties doesn't it?) and also from a rather shoddy speaker installation. Now I just need to figure out where that wire actually should disappear under the car. The sender did measure open when I originally checked I'm 90% sure but I'll obviously need to hook this back up properly either way or the gauge won't work even once the sender is changed! I did have a poke around underneath but couldn't immediately see where it went - though it's hard to see anything useful given there's a whole load of suspension and brakes in the way. Car really needs to be up on ramps to see anything much at all. That's a job for future me though

You must have the patience of the saints stripping out the gauges like that.. id be worried about breaking the plastic..

On a different note ... an Invacar is available ...

https://www.facebook.com/marketplace/it ... 985348431/

Could you fit a modern motorbike engine to replace the original trabant motor or would you prefer to keep it original?

rich. wrote: Sun Jun 30, 2024 7:48 pm You must have the patience of the saints stripping out the gauges like that.. id be worried about breaking the plastic..

To be honest that was definitely a worry going into that job, but the instrument panel on the P6 comes apart really easily. Aside from the somewhat questionable choice of board-to-board interconnects from a long term reliability perspective it's really quite well thought out and very service friendly.

gazza82 wrote: Mon Jul 01, 2024 10:27 am On a different note ... an Invacar is available ...

https://www.facebook.com/marketplace/it ... 985348431/

I recognise that one, and the username. They have had quite a few though their hands over the last few years I believe. It's astonishing to see the prices they seem to be fetching now given that they were basically just considered a joke ten years ago. Granted people do seem to pay quite a premium for a lot of microcars it feels like.

rich. wrote: Mon Jul 01, 2024 8:38 pm Could you fit a modern motorbike engine to replace the original trabant motor or would you prefer to keep it original?

It's been done with quite a few engines over the years, though I don't believe there's anything available off the shelf that can just slot in, nor a pre-made kit with all the bits you need. Probably the closest would be provision for slotting the three cylinder Wartburg engine in - though even that's quite a lot of work and involves having to mess about with liquid cooling. Those engines aren't exactly cheap these days either. Then of course also comes the added hassle of insuring it, and more often than not you'll find that cars with a non original engine in - even if on paper vastly improved over the original - have lost a lot of value if you do come to sell them. Admittedly that side of things really isn't high on my own priority list.

I'm also a bit wary of bike engines going into cars in general as so often the completely different power/torque curves just don't match the very different applications. I used to know someone who had a bike engined Suzuki Cappuccino, and while I'm sure it would have been an absolute blast on a track, actually driving the thing on real roads, especially in town was a near painful experience. It was a never ending balancing act between trying not to stall it when moving off yet also not propelling yourself through the car in front of you.

For me at least the car needs to remain two stroke. Taking that out of it would just take away so much of the character of the car that it would be a shame. Plus it's hard to argue with the level of support out there there is for the original power unit. No some of the parts aren't cheap, but in the same breath there are a lot less of them! I've not really run into any particular design issue here, it's just worn out, which given the 135K km on the car isn't all that surprising, especially as all evidence suggests this car has never lived a particularly pampered life. Just a bit of bad luck that whatever has originally contaminated the crankcase (and this could have happened a long time ago, we just don't know) has resulted in scarring there which means it also needs to be replaced.

Given the sheer number of bits I need to replace (basically everything of the core unit save for the heads, ignition breaker assembly and possibly one cylinder), and that a sensible looking secondhand unit hasn't turned up. Couple of leads on Facebook but as always seems to be the way once I contacted folks directly to actually ask questions beyond their "I've got one" response the result was deafening silence. So looks like I'll have a sizeable bill and a heavy box on the way from Germany soon. I just need to run some numbers and decide exactly which of the three options in front of me makes the most sense as I've not really done direct comparisons yet. Also need to factor in an allowance for some other parts which I'd be daft not to change while everything is apart - engine/gearbox mounts and the very judder prone clutch immediately spring to mind.

As seems to have become customary I've fallen behind here, so have a few updated bundled in together.

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Much as I despise working under cars that are jacked up, no matter how many axle stands are involved, I really wanted to see if I could get the fuel gauge reconnected.

Blindly waving my phone around in the vicinity of the pickup and taking photos until I got something useful revealed that the wiring was still connected to the sender. I was pretty sure this was the case beforehand as I was sure I'd tested it and found it to be open. Though what I couldn't remember was whether I did this at the tank or whether I'd tested it from the relevant terminals at the dash.



That's looking pretty much straight up from just forward of the diff - front of the car is top of the frame.

I couldn't find any angle I could see this from in person. From the back I could just about reach it with one hand while I was basically eating the cross bar on the rear suspension. That's a definite downside of the Di Dion tube setup...it's in the way of things no matter which side you try to sneak up on what you're trying to work on.

Eventually I did spot where the end of the wiring was floating around. This is looking towards the front of the car - offside rear wheel is to the right of the frame.



Trying to strip that back to clean wire and connecting new leads to it was precisely as much if a pain as you'd think given I was working with one hand essentially stretched out as far as I could reach up above my head.

Yes, I used Wago connectors. This will be done "properly" at some point in the future when the car's on a lift or proper ramps. This is just wanting to get things hooked back up so I know what I actually need to fix when I can get to it properly.

Turns out that I was correct about the pass through in the boot floor being the cable's route, this is where the wiring was meant to run through. However it does actually just go straight under the car, I originally thought it went into a box section.



Wish I'd realised that sooner as it would have made my routing of the fuel return line far less of a pain!

As expected this hasn't actually restored function of the gauge - but the sender I was already pretty sure was knackered.

The cooling system definitely seems to require some more work though. Not sure whether I'm just seeing higher readings now because we always had a voltage supply issue on the instrument panel before, or if I've just been running the car longer. Bumbling around in 30/40 areas it sits bang in the middle at 85C, but driving on any higher speeds roads it creeps up to what I reckon is about 95C. Sitting stationary it definitely starts to creep upwards after five minutes or so. Exactly how FAR it will creep I don't know as I chickened out when I got to here.



I know the radiator isn't in the best of shape. Both end tanks have had several repairs in the past and I can see that the fins have separated from the core in a few areas - based on all of the above it's not unreasonable to expect that it's not flowing the best either. It will need to be replaced - sadly having talked to two radiator specialists they both deemed the end tanks in sufficiently poor shape that they'd not be willing to re-core it. They'd happily make me a replacement using the original as a template - for somewhere in the region of £650 plus VAT. So I think I'll have a bit of a hunt for a more reasonably priced option given the bill which will be landing soon for the Trabant. I'm not going to lose sleep over finding the automatic specific one as the transmission can just get a stand alone oil cooler installed when we get to that level on the snagging list.

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With the Partner in work commuting use, the Invacar still boxed in behind a broken Trabant, the Trabant having only half an engine, and the Renault still as far from being road ready as it was at Christmas, the Rover was placed on Daily duty.



She actually behaved based on the history to date very well. Still running a touch warmer than I'd like but not too worryingly so, the windscreen wiper blades are utterly hopeless, and that blasted sidelight has gone out again. The holder in that just needs to be replaced really as it's knackered. If I clean the contacts it will work again for a couple of uses before packing in again.

Niggles aside though, we did probably 30 miles over four or five errands dotted around town, and she just did car things without complaint. Do I dare believe that we're starting to turn a corner with things towards the car being properly usable? Or do we have another exciting random failure waiting to pounce as soon as I believe that? Don't know, but I'm sure we'll find out soon enough.

Now that we've got that oil leak under control I think I just need to make a point of using the car a bit more and try to get some miles covered to shake the remaining bugs out.

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Sidelight has been repaired. Again.



The whole back of the cluster is just rotten though so I don't expect it to stay fixed for more than five minutes. Annoyingly I did get a couple of spare tail light assemblies with the car but no front ones. The little light pipe at the top of the lens does work quite well to show you where the front of the car is after dark (even if the one on the driver's side has been snapped off sadly).



Additionally to properly fixing the wiring to the fuel gauge, I really want to get this car up on a lift so I can properly get a look at the rear suspension. There is a very noticeable difference in the ride height between the two sides.

Nearside:



Offside:



I did have a look around while I was wrestling with the fuel gauge wiring and couldn't see anything that looked obviously amiss like a broken spring, but something is obviously awry. Not sure if maybe there was a broken spring at some point and only one was changed - so one is relatively new, and the other has 48 years and 101K miles of wear on it? Answers on a postcard please.

Finally having got some hose of the correct hose in stock I was able to get rid of this randomly blocked off vacuum port on the hose to the brake servo.



I'd ascertained already that it wasn't entirely sealed, but additionally the hose was a good couple of inches too short so was firmly wedged up against the back of the alternator.

Much better.



Also added a couple of hose clips to the vacuum line between the two halves of the servo as that line was quite a loose fit after this many years. Evidently this improved matters as first time I went for the brakes after doing this I just about launched myself through the windscreen.

Having fixed the sidelight meant I could have another shot at getting a halfway decent photo of the car.



Still breaks my brain a little to think how long ago this design was drawn up. Not quite as much as it does to drive the car mind you. It absolutely doesn't feel like a 60 year old design.

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It's funny to think that the P6 was considered a proper full size family car when it was launched. However it even makes the Clio I parked next to today look positively bulky. Never mind the eyesore SUV on the other side.



A maintenance job I'd never really properly tackled since I got the car was to balance the carbs. I had a feeling that the engine was mostly idling on the offside carb just from the sound of things and given that that bank seemed to be running significantly warmer when I was doing some temperature checks last week.

I don't have a proper carb balancing kit here. Not least because this is the first car I've owned which had more than one carb so it's just something I've never needed before. I do however have an off cut of fuel hose, enthusiasm, and a reasonable understanding of how these things work.



Simply put, just disconnected the throttle linkage between the two carbs, then used the hose as a stethoscope to listen to each intake as I adjusted things until I got both the desires idle RPM and the same amount of air being drawn through both carbs. The linkage was then adjusted to compensate for the rest position now being slightly different (as predicted, the car was really heavily leaning on the offside carb with virtually nothing being done by the nearside one at idle) and reconnected.

Given that there were no real signs of carburation issues present I opted to just leave everything else well alone - I'm sure 90% of the carb issues that people run into are down to twiddling adjustment screws when there really was no reason to in the first place.

Idle speed is sitting at 700-750rpm in neutral, dropping to 550-600ish in gear, which sounds reasonable enough to me without having the book figures in front of me. It does occasionally hang slightly higher, but that seems to be down to the throttle pedal linkage rather than anything at the carb end.

Definitely sounding a lot better now than when she arrived here.

YouTube Link

The exhaust is generally pretty subtle compared to what a lot of V8 cars seem to end up fitted with, the one exception being just how bassy the rumble at idle is, which I'm not sure if the mic will ever really pick up.

While I had the air cleaner off I took the opportunity to finally ask a question about what this unused hose connection on the back of the air cleaner is meant to be used for?



I've never seen anything floating around in the engine bay which would likely have been meant to connect to it. Given the surface rust on it I don't think it's had anything attached for a good number of years.

Evidently I do need to do some more leak searching on the cooling system as there's a bit of coolant which has gathered on the valley cover. Given the slope on our driveway and how the car is parked I'd expect this to pool at the back like this, which is why I'd not spotted it until I had the air cleaner off.



It looks like a lot there but one paper towel was fully able to soak it up easily, so not actually a massive amount. Those heater hose clips are both secure (the lower one is actually on there fine - the fitting the hose goes on to extends a long way into the hose). I'd be tending to look more suspiciously at the thermostat housing or the connection up front to the lower heater hose as they're really quite awkward to connect up as there isn't much space to play with.

Not trying to do that now though while the engine is hot. Same reason I've kicked looking at fine tuning the kick down cable adjustment down the road - trying to do that now is just a recipe for burned fingers.

Last thing I did today was to provide a bit of protection for the coolant bleed line that runs between the top of the intake manifold and the top of the radiator.



This was chafing on the alternator belt shield - and given the direction the fitting coming off the radiator points I really don't see how it's meant to go anywhere else.

I realised when going to secure this though that I'd somehow actually managed to run out of zip ties...so securing it properly will need to wait until I've had a chance to pick some more up.

-- -- --

Hopefully I've found the cause of the water sitting on top of the valley cover.



That's a new hose and the clip wasn't very tight. Hopefully it had just loosened a bit as the hose compressed. Have wiped it down and will see if the water reappears.

I've lost track of how many applications have been made now, but the leather is definitely improving compared to the cardboard like texture it had when the car arrived here.





Would be good to get some dye on it at some point to bring back out the original colour. If the above was already too much orange for you, look away now.



Definitely not an interior colour choice for everyone this. However I'm rather partial to bright colours in cars so suits me just fine.

I mean subtlety isn't really what this car is about is it?

P6 has been out and about again today. For the first time I took it out for an errand run, albeit a short one, and wasn't actively nervous.



Had someone again call out as I was leaving the car park to compliment the car. It definitely seems to be turning heads!

That's 60ish miles done over the last week, which is by far the furthest I've gone so far without something new going wrong or falling off. Trying not to let it know I've noticed.

Tiny fix today.



The little swinging covers over the keyhole on both front doors were being actively held away from sitting where they should be by their springs. Things are now lined up properly I think so the covers sit where they should do.

Really like the door handles on this car. They have that really satisfying design that is a perfect balance between being very deliberately designed, but not OVER designed. Feel really nice to use as well. I do need to adjust the hinges on the remaining three doors a little though as they catch slightly when opening. Driver's door was the same but that one got adjusted as unsurprisingly it's the one I use the most.

Great to see the rover back in use
I've looked at wadhams via Google and a reconditioned radiator is about £220. Not sure if it's helpful.. I'll try and find a link later

https://www.ebay.co.uk/itm/335445291531 ... R8D4yOqWZA
https://www.jrwadhams.co.uk/radiator-3500-auto.html