Air lock or Head Gasket that is the question

[Rickyrjb]

Well as some of you from todays little blat will know I am having trouble keeping coolant in the engine.

So what happens, I make sure coolant level is full and I dont think I have any air in the system, can drive the car for as long as required as long as I dont stop the engine, as soon as I switch the engine off it then dumps the coolant out the expansion tank. So now I need to top it back up.. takes about 1.5ltrs to bring the level back up again but as its hot I am not 100% sure I have all the air out, drive again and stop = same again.

PS: When its running right its bang on 90 deg, you can see the tempreture drop on the gauge when the stat open when warming up.

I am thinking more head gasket than air in the system, however
1. The oil is clear and like new still.
2. No white steam from exhaust
3. Water is not milky or any foam (but it not in there long)
4. No external signs on the block of oil or coolant leaks

The rad cap on top of the expansion tank is rated at 15lbs, could this be too low, should I ditch the pressure release cap and seal the system to try and stop the "blow out"

So best way to check if you have a failed HG, test coolant for gasses present.
Anyone every used a block test kit ??
https://www.ebay.co.uk/itm/CYLINDER-HEAD-and-BLOCK-LEAK-TEST-KIT-Petrol-Engine-Combustion-Leakage-Tester/264235979232?hash=item3d85b111e0:g:Yk0AAOSw-V1ch440

Any thought????

[Rickyrjb]

Oh and it was on a dyno on Thursday and made 180hp so surely cannot be a head gasket... can it

[Matth93]

what you could do is try running the engine up without a cap on it and see if you get air bubbles appearing in the tank, if you do and they just keep coming it could well be head gasket.
Don’t run it with a sealed cap as it will just blow something else when it gets too much pressure.
You might even be able to smell exhaust gas in the expansion tank

[b33fy]

I’ve used a sniff test previously, though not sure about the sensitivity, where you’ve changed the water it is unlikely to show a positive unless the engine has been run for considerable time.

[nelmo]

Oh and it was on a dyno on Thursday and made 180hp so surely cannot be a head gasket... can it

Was it doing this before the dyno run?

[nelmo]

So best way to check if you have a failed HG, test coolant for gasses present.
Anyone every used a block test kit ??
https://www.ebay.co.uk/itm/CYLINDER-HEAD-and-BLOCK-LEAK-TEST-KIT-Petrol-Engine-Combustion-Leakage-Tester/264235979232?hash=item3d85b111e0:g:Yk0AAOSw-V1ch440

Not personally but this guy did - worked well for him:

https://richards-gbs-zero.blogspot.com/ ... until.html

[Dick]

We use the test kit a lot in the workshop never had a problem and good results from it . Its not the cheap ebay one .

[Dick]

If it was me i would check the depth of the rad cap face against the rad cap you have before you start spending money and its easy to do

[Dick]

If it was me i would check the depth of the rad cap face against the rad cap you have before you start spending money and its easy to do

[Rickyrjb]

OK so new rad cap fitted and made some changes to the expansion tank and overflow arrangements, and guess what.. no difference.

So after today little shakedown I jacked the back of the car up as high as i could get it, which was about 30deg and re filled the coolant again. Then whilst the car was jacked up I ran it for few minutes and guess what, a constant stream of small bubbles in the expansion tank. So I am now pretty sure its a head problem, I am going to try and borrow a gas checker tommorow but I now almost certain its going to be a head job.

So basically the head gasket was gone when I swapped the engine as its been having this problem since I swapped the engine pre lockdown. Lesson learnt I should have taken the head off and fitted a new gasket at the time.

Will keep you posted on progress

PS: That now explains why Tony got passed me today on the Camber straight!