Topic

Taking an interest in this topic as mine may also be losing coolant from no obvious place so I gazed through downloads and “head gaskets” by Russel and David. Both list this as a possible problem
“Leaking inlet manifold gasket - A leaking inlet manifold gasket can show as (a) a cold start misfire (b) coolant staining down the block, gearbox side (c) coolant dripping on the floor or a mixture of the three.”

I’m at a loss to see how a leaking inlet gasket can be a source of water loss. I have looked at the inlet gasket on Rimmers site and can’t see porting for water. So how can water be leaking from there ?
Can someone possibly help me understand how that can be?

Trust me it does,

Ok, I believe you, but how?
The inlet manifold is there to direct air into the cylinders along with fuel.
So unless the manifold is heated with water and the manifold has a dual role acting as a water rail along the cylinder head how can it leak water?
Where is the water going to come from?
Please clarify.

The inlet manifold gasket covers two water ways in the head so can cause both external leaks and also leaks directly into the intake ports.

Thank you for that explanation as that makes sense.
At present I seem to be adding coolant as the level in the expansion tank falls by about 10 to 12 mm after a relatively short ride around and is perhaps getting worse.

Brief history. After cam belt change just over 12 months ago all seemed fine. A decision was made to replace suspect compliance bushes and this would have involved releasing the cooling hoses and lowering the engine/subframe. Return journey home about two hours and 80 plus miles and again all seemed fine. Then after the next outing back in Oct last there was a small drop in level within the tank. Since then the car has had little or no use other than a test run following suspension component replacements. The level in the tank does seem to drop after these brief rides. However, there is no loss on the garage floor (which is painted white and in parts has cardboard acting as a catch-all under the centre area of the car). When fixing the reversing switch and with the engine hatch off there was no obvious staining.
When draining the oil for a change there was no evidence of water in that oil and no "mayonnaise"

So I'm clutching at straws to see if I can establish where the loss of coolant is taking place. The inlet plenum is metal and presumably the intake manifold too (but of course it is wrong to assume). So if a metal inlet manifold does that mean that the inlet gasket is less prone to leaking water or not?

Metal inlet manifold is somewhat less prone to gasket failure, but that is not something you can count. If you have problem in starting of excessive white smoke from exhaust that would point to inlet manifold gasket problem. 10-12mm is not small amount, so you should see it somewhere. When was last time you replaced water pump?

Yes, I agree the loss is not insignificant. The water pump and cam belt were changed together in Feb 2023 (since then and with exception of about 20 or so miles) the car has done about 1400 miles. There was no loss observed after the water pump change other than from the hoses at the underfloor cooling pipes. Once they were "nipped up" there was no loss until after the lowering of the engine/subframe to renew compliance bushes, and even then I don't think it was immediate i.e. not during the run home from the repair garage ~ although that is now over 6 months ago and the first loss was observed a week or so after that and believing that to be air in the system thought nothing of it.

I agree it should be visible somewhere but its not obvious. As stated above the use this year has been negligible due to repairs and weather.
The logical place would be the hose connections to the underfloor pipes particularly at the rear but there is nothing showing there. The pipes are stainless.
For various reasons access around the car is restricted but the last time I was in the car (fixing an electrical supply to sat nav/dash-cam) I got the sensation that the carpet on the off side was a bit damp but on feeling again I discounted it as just cold and there is no typical odour. The car has not been out in the rain since mid last year.

My intention is to run it tomorrow and see if I can find anything around the radiator or possibly the radiator and heater bleed screws.
Edit, apologies omitted to say that there are no problems starting and no white smoke on starting up that I have observed.
There is no staining around the heater bleed point or around the radiator bleed position. One of the jubilee clips to the water pipes has been nipped up a little to match tension on the other pipe.

I am pleased if not relieved to report that tightening one of the two jubilee clips between hose and underfloor pipe has resolved the situation. It took about 1/3rd of a turn on the screw to tighten it up.
Prior to that there was no evidence of a leak on the garage floor and I can only conclude that pump pressure when operating at higher rpm than idle was sufficient to force a leak once the thermostat had opened.
So after at least three cycles and about 60+ miles I’m happy to continue to monitor this as there has been no loss since tightening that clip.
Thank you all for the comments and help.

Nice when you know job is done.

That's really great news that the problem proved to be something that was easilly resolved.

Posted by mistake