How to pressure test the coolant system?

[Barry.b]

Hi guys
I am looking for a bit of help please.
I have done a compression test on all 6 cylinders of my engine and I am getting 182psi in each cylinder.
I am loosing coolant in a BIG way.
I rebuilt the engine 8 years ago and I am only now getting it back in the car.
I got it started for the first time ever since I have owned the car ,
I only ran it for about 5 or 6 seconds when I turned it off and noticed coolant dripping from the camshaft oil drip feed pipe.
I was gutted .
I might have fitted the wrong head gasket perhaps or maybe the head or the block are cracked.
I really hope it is the gasket !!!!
What pressure should I pressure test the coolant system to ?
I am not actually sure if I can build any pressure in the coolant with a test rig as I think I might be just filling the block and radiatior up to the level of the head gasket then I am probably just filling the sump with coolant after that
But it would be good to know the number anyway.
From memory my engine shop did pressure test the cylinder head , but they did not pressure test the engine block.
Thanks again guys

 

[stphers]

What you can try if you have compressed air available Top up your rad right to the very top edge of the rad cap area. start with #1 cyl I remove the valve cover so I can see the lobes, especially when I am looking at the overlap. Bring the eng up to TDC on # 1 with # 6 cyl valves overlapping This is just like doing a leakdown test only you will be looking to see if the coolant level rises It won't tell exactly where the coolant leak is but that you have one. When doing this, I bend the air line and let the air into the cyl slowly, lot's of times, the eng will kick over because ypu don't have it right on that sweet spot where piston is all the way up and both valves are completely closed You can go thru all the cylinders by the firing order and confirm by looking at the overlap on the sister cylinder ( 1 & 6, 2 & 5 and 3 & 4 are sister cyl ) when one is at tdc compression, the other one will be at TDC on the overlap. If the head gasket is gone, or the head cracked or ( heaven forbid ) the block is cracked, coolant will be pushed up past the top of the rad opening Used to get some real gushers back in the day when it seemed that all that I did at the dealership was replace 6 cyl heads
Hope this helps

Thanks, Rick

 

[Barry.b]

What you can try if you have compressed air available Top up your rad right to the very top edge of the rad cap area. start with #1 cyl I remove the valve cover so I can see the lobes, especially when I am looking at the overlap. Bring the eng up to TDC on # 1 with # 6 cyl valves overlapping This is just like doing a leakdown test only you will be looking to see if the coolant level rises It won't tell exactly where the coolant leak is but that you have one. When doing this, I bend the air line and let the air into the cyl slowly, lot's of times, the eng will kick over because ypu don't have it right on that sweet spot where piston is all the way up and both valves are completely closed You can go thru all the cylinders by the firing order and confirm by looking at the overlap on the sister cylinder ( 1 & 6, 2 & 5 and 3 & 4 are sister cyl ) when one is at tdc compression, the other one will be at TDC on the overlap. If the head gasket is gone, or the head cracked or ( heaven forbid ) the block is cracked, coolant will be pushed up past the top of the rad opening Used to get some real gushers back in the day when it seemed that all that I did at the dealership was replace 6 cyl heads
Hope this helps

Thanks, Rick

Hi Rick
Thanks for the advice, did you use a fitting to connect the air hose to the spark plug threads , or was it just a snug fit in the spark plug hole ?

 

[Ian C]

I had the same issue with my m90 rebuild. In my case solved by using a factory head gasket, the lands were too thick or maybe wrong metal as they were about 5 thou proud of the gasket material when disassembled, allowing water migration to oil galleries. This was before final torque step, didn't want to run it up to temp with the water leak. If you don't want to spend factory money, assuming this is the cause, Elring supply the factory. Best of luck Barry, I feel your pain

 

[stphers]

Hi Sorry should have said that I used my hose that screwed in from my leakdown tester, just removed the safety valve in the end or you could use an old spark plug, gut it and attach a hose to it with an air fitting at the other end

Thanks, Rick

 

[Barry.b]

Okay so
I connected my compressor up to my cooling system this evening and I pressurised it to 1 bar.
It didn’t hold the pressure
The pressure did not go into the cylinders as I tested that too by blocking each spark plug hole by hand and no increase in pressure was felt.
I cannot see the leak I can only hear it !
Does anyone know which ports supply the oil under pump pressure to the head
I might have to check each set of chambers in the head
I have already checked the combustion chamber they are all fine .
Then the oil chambers/ runners should be tested
Then the coolant chambers should also be checked