Full expansion tank

[alan c]

Hi some advice would be welcome.
I check water oil etc every day car started, coolant level in expansion tank is always about half way.
Sunday I traveled from Durham to the CITP @ Newby Hall, next evening done normal checks to pull car out to wash and noticed coolant in expantion tank was full to the top.
The car ran fine on previous day and now oil pressure/temp guage fans cutting in and out everything as normal.
This evening checked expansion tank cap on tight, started engine let run about 15 min to warm up till fans cut in, turned heaters to hot.
Oil pressure normal, temp when fans cut in normal(mine have lower start temp fitted by previous owner 70 c)
Blowers where warm(just)
Swirl pot hot
Radiator top and bottom hoses hot
Radiator was cool
Expansion tank cold
The oil and coolant are very clean.
My thought was cylinder head gasket, but advise on fault or futher test would be appreciated.

[yellowgriff]

Don't panic yet.. if it was a head gasket it doesn't make more water. water should be about a third full don't over fill thats why its called a expantion tank for when water gets hot & expands..Also most time you will get gung in oil filler cap.sounds a bit like a air trap if your heater i luke warm..
IMO give the car a few more runs & keep checkng... If your car is running o k don't keep checking every trip it will give you Knight mares..
Hope this helps

[moorcroft]

I agree with yellowgriff about not panicking and continue to monitor!! However this was exactly the same symptom that showed my head gaskets had started to leak. Leak is the appropriate word, because as they are tin gaskets they rarely completely fail like a composite gasket. I had no oil/water contamination at all and car would run at a normal temp, however compression from a cylinder was escaping and entering the water jacket. Small bubbles collect in high points around the cooling system, therefore level in expansion bottle rises. I would recommend regular bleeding and monitoring but if the system continues it looks like HG. Bear in mind my car would go about 100 miles before enough air had entered the system to blow the pressure cap and displace coolant.
Below is a picture of a tin gasket at varying degrees of failure. By the way, if your car has 14 head bolts instead of 10 then the risk of HG leaks is increased, see picture!!

[JonathanT]

hmmm, I had the same symptoms too - expansion tank always "filling up" but never overflowing. Later I could hear bubbles of air working their way into the expansion tank just after pulling up from a run and later still there was a little oily tide mark around the top of the tank.

This *was* a leaking head gasket and again, no catastrophic failure.

[moorcroft]

Like jonathonT said, I also could hear bubbles once id pulled up from a run!! A final confirmation of having the coolant tested for the presence of combustion gases confirmed the gasket was leaking. The reason alot of people don't diagnose a hk leak is because of the way a composite gasket fails (loads of smoke/steam or oil/water contamination), however the tin gasket used on these engines start with a v.minor leak and slowing and progressively get worse.

[TVR Beaver]

My tank will inc in volume about 1" moveing from the garage to the drive... about 4 mtrs... just on / off... something to do with moveing the water from one side of the stat to the other... When you parked it the stat we open.. .now it's closed etc... And leave the cap off and is soon comes up the tank..... also even if my car is warm... the level is much higher... it needs to be slap cold to get accurate reading.... How old is your car.. the newer ones have composite head gasketts not metal... if one of these goes you usualy know about it... that said keep listerning for bubbles after a run.. if you get this then yes the head gaskett has gone... but wip the cap off before it's cooled and it could be close to the top!! B