Renault 4 Head gasket?

[freelancewriter1]

My 1993 Renault 4l Safanne has suddenly begun to overheat. Took out thermostat, no difference. Changed radiator, no difference. Now I can see regular bubbling in expansion bottle!!
Has anyone any experience of these engines and their foybles please?

[JPB]

There may simply be a leak on the small hose from the heating pipework to the water pump, in which case, assuming that you haven't driven it like this you'd get away with replacing that hose most times. However, this is most likely head gasket trouble, to confirm this you need to check whether thae bubbles are a result of exhaust gases in the cooling system which would tie in with its most common failure mode. Take it to a garage for a hydrocarbons test but please, don't run it without the thermostat, this will make the engine more likely to overheat catastrophically.
These heads tend to warp - and can crack around the valve guide bosses where they're in contact with the water jacket - once they've been run with a failing HG as yours most likely has so budget for a pressure test and reface, usually around £40 more than a basic gasket swap as the garage will need to send it off for testing.

Well worth it though, IMHO, as these big Renaults are massively undervalued and a superb car when all is well.

[Topaz]

Well worth it though, IMHO, as these big Renaults are massively undervalued and a superb car when all is well.

Big Renault ?? - to my mind I always thought of the 4 as being a relatively small car - certainly in comparison with modern vehicles when anything old looks small

Mike

[mach1rob]

I assumed a 4, but then I saw

My 1993 Renault 4l Safanne

so I can see why John mentioned the Safranne

[freelancewriter1]

Sorry folks its a 4L Savanne, yes it is small and lively when going. It was one of the last 4l 's built.

Its been fine for the last year then suddenly hot! Originally thought the thermostat was at fault as took it out and tested it and it wouldn't open in boiling water.

Can't really see why running without thermostat in this little (998) engine should be a problem?

Unfortunately the bubbles are pretty regular although did not notice them at first. The engine I believe has wet liners that can leak at the bottom but that should produce crank case pressure.

Oh, and it starts first turn of the key and no missing or miss firing. No exhaust smoke or steam.

Any more advice?

Thanks,

Keith in France

[JPB]

Yes, get it tested for gas at a garage, the heads on these Cleon/Sierra engines suffer the same as most aluminium ones do and, when they fail, it's usually from an eroded fire ring in the HG (usually number 1 IIRC), hence the bubbles. Additionally, their wet liners aren't solidly attached to the block and can move so watch that when lifting the head off. There's only a thin layer of Silicoset or similar to prevent the coolant entering the sump which is misleading in this engine as that's rarely a symptom of HGF like it would be in an engine without liners of this type so get the sniffer in about at it.

Running without a thermostat is a bad idea regardless of the capacity of the engine though.
Thermostats are cheap but fuel isn't and the little OHVs found in the 4 should run at around 85C, by not warming up sufficiently not only will you be cold in there but it'll waste fuel and exacerbate wear by washing its overly rich cold fuel mixture down the bores.