Hi all, I think my n/a has developed a head gasket leak:
The car overheats and it doesn't matter how much water I put in the overflow tank, it soon disappears when the green pressure cap is put on
You can see fluid being ejected from the little hose from the thermostat housing into the tank
White smoke from the exhaust--- on idle
No water in the oil
Heater has been by passed
No visible external leaks around engine or radiator
Thermostat removed
When I pulled the spark plugs the engine was hot and there was no evidence of water or anti freeze on the plugs--I would have thought with the speed the water disappears I would see something
Don't have a code reader
No compression test as yet
Am I on the right track
Regards David

Finally found the time to re move t he head and whilst nothing leaps out at me, i notice that I have a copper brown discoloration ( minor ) but a little like the picture of the gasket posted by repairman jackal. Thankyou.Mine is between cylinders 3 and 2. The head has gone to the machine shop and I hope to have it reinstalled in a week or so. Fingers crossed.
Regards David

Will do. I am getting a full head service, so it should be good. Will check the pcv as well.
David

The head surface should still be flat. But, while the head is off, I suggest replacing the valve stem seals as they do wear and leak oil. There are only 20 of them...

No issues there James, the car runs nicely and all plugs are clean and the same color. David

If you go to start it and it stops turning over, or does not want to turn, you might have a cylinder full of water.
--
'96 855R,'64 PV544 driver, '67 P1800 basket case, '72 Yamaha Rd400, '68 Honda 350-4, '12 XC70, the first 5 are mine, heh, heh, 525,000 miles put on 10 bricks James A Sousa

hi Klaus /Repairman jackal, today i looked around the water pump-no leak. Idid a compression check, engine hot-180-185-175-185-180. When i removed the thermostat the other day , it was broken and jammed almost closed. Could this have caused an airlock or other problem as to my mind the compressions look ok.Thoughts please. David

When the thermostat is closed, the antifreeze will reach boiling point rapidly without anywhere to vent, except through a very hot head gasket. #3 compression, while not serious yet is a bit low and may bite you later.

Go ahead and run the car for a bit without a thermostat, you mpg will be poor because the ECT sensor will be cold. Or put in an OEM thermostat. Cheap aftermarket jobs will kill an engine because they almost always fail in the closed position.

In either case, you found the cause of the problem. Steam can work its way through most anything where water cannot. Monitor it for a while to see if the fluid level goes down a lot or stabalizes. And save up for a headgasket.

I was just thinking Klaus, and the car has done over 200k, I have changed a belt but not a pump ( previous owner had) and if I removed the timing belt cover should I see evidence of this leak due a faulty pump. David

By all means, remove the T belt cover and take a look with a flashlight. Even reach down there and grab the cog for the pump and see if it moves - like a bad bearing.

I forgot how much water you said it uses up, but if it is steaming out of the tail pipe and the steam smells bad from antifreeze - head gasket. A compression test will tell you for sure.

Usually, a leak like that will only happen after the engine is warm and turned off. That is when the hot water pressure will be the greatest.

All the plugs were very clean, but were all the same. If the water pump was the issue, would I see water on the engine or ground ? I am amazed that it swallows so much water with no obvious place for it to go. David

If antifreeze is entering a combustion chamber you will see a very clean spark plug and piston. This will not happen to all of the plugs, just one or two.

Depending on engine hours (mileage) you also need to look at the water pump and check for failure. Hopefully, no one replaced it with non-OEM plastic vaned type.

Removeing the thermostat was a good move, but that also means that the engine should not overheat or even get close to the red zone, so long as the pump is working and the ECT sensor initiates the fan.

I encountered a post on Volvospeed where a person installed a clear plastic hose between the thermostat housing and the upper radiator hose. He could then verify that fluid was moving and the pump was good.

Am away from home at the moment and will have a look at that one next week. No water leak from the cap. David

that doesn't sound too good.

Is any coolant escaping through the cap? Do you see roiling bubbles in the expansion tank when you rev the engine?

You might have one of these problems...