Hi,

I wonder if you could help.

My friend has a 2004 4.4v8 with the BMW m62 engine. The car runs really nicely and but recently the water pump gasket has gone and now the valley pan gasket. It has never overheated in his ownership. The car has done 176k miles.

As a check we bought the head gasket failure liquid that changes colour with combustion gases from the expansion tank. Unfortunately this has changed colour on multiple checks indicating combustion gases in the coolant. We then compression tested the engine and all cylinders gave approx 160psi.

I am handy with spanners but wonder if anyone else has any opinion of whether it is head gasket and if it is do the heads tend to crack or warp on these engines?

Look forward to hearing anyone’s ideas.

Thanks

Welcome aboard......before we go any further.....is it fitted with lpg ?

Thanks for the welcome. No it is not on lpg.

Well we can rule that out then, hg failure is not unheard of and at that milage water pump and valley pan gasket isnt surprising either.

Some kits for testing combustion gasses are better than others was ut a decent kit ?? Or cheap bay of e ?

It was an eBay kit but we did test it on two good known petrol cars and it stayed blue coloured.

Can you suggest any other kits or where we go from there?

Do the heads normally warp or is it ‘just’ a case of swapping the gaskets?

Thanks

If you tested the kit on known good engines it's fair to say it's ok.
As far as hg go I dont think there is a normal we rebuilt an m62 engine a couple of years back the previous owner had boiled it dry of cooland and engine oil on stripping it down the hg were still good.

Odd that your compression test had such good readings...

The kit definitely worked by changing colour in the presence of co2. With the two known good engines it stayed blue. Then when we bubbled exhaust gasses through it turned instantly yellow.

This is what we are sort of struggling to understand. Why the compression tests are good yet the combustion gas test is coming up that there is a problem.

Thanks

Hello Toby, you say you've done a compression test, but have you done a cylinder leakage test too?

Compression test; imaging trying to blow up an empty crisp packet with the other end torn open. You're never going to do it.

Cylinder leakage test, imagine trying to blow up a crisp packet that has a pin hole in it. You'll blow it up but it will eventually go down.

Carry out a leakage test, that is a far better indicator of a problem than a compression test for this kind of suspected issue.

Sam

At that mileage I think if it's running OK and not spewing up coolant after 15mins sat in traffic then I'd leave it well alone... just my 2p...  Pete
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Sam wrote:

Hello Toby, you say you've done a compression test, but have you done a cylinder leakage test too?

Compression test; imaging trying to blow up an empty crisp packet with the other end torn open. You're never going to do it.

Cylinder leakage test, imagine trying to blow up a crisp packet that has a pin hole in it. You'll blow it up but it will eventually go down.

Carry out a leakage test, that is a far better indicator of a problem than a compression test for this kind of suspected issue.

Sam

Haylands wrote:

At that mileage I think if it's running OK and not spewing up coolant after 15mins sat in traffic then I'd leave it well alone... just my 2p...

Bite the bullet and pull the heads if it his intention to keep the car

Yes I'd agree, it's normally a very good indicator as in most engines a compromised head gaskets is the only way exhaust gasses can get into the cooling system unless you're really unfortunate and have a cracked head, or worse, a cracked block.

The thing is though, from your description it's only a minor leak, and this is where a leakage test comes into it's own. A compression test is fine for things like burnt valves or knackered rings, but if you only have a very slight leak (Crisp packet with a pin hole in it), a sustained pressure test, or cylinder leakage test will show it.

The other thing it'll do is highlight which bank the problem is in. So if you really only wanted to remove one head (Not really recommended), you could.