Is it a cylinder head problem?

Post by **Jamie25** » 25 Jan 2008, 18:25

Further to my post 'Strange Overheating???' (thanks for all the posts).

To cut a long story short, after repeated overheating I've replaced expansion tank cap and thermostat with genuine parts and flushed and bled the cooling system.

I can't seem to find any leaks but I'm loosing water and it's overheating after about six/seven miles. Getting (very) hot air out of the heater but the radiator isn't getting hot or only gets hot in the bottom half. Top up tank is often very full after a short run.

Pressure tests reveal 10.5, 10.25, 9.5 and 8.5 bar with a warm engine. When engine is warm and running with the expansion tank cap off the water bubbles like mad. It also raises and lowers with engine revs.

I think this fairly conclusivley leads to cylinder head problems except i think th epressure test results are acceptable????.......but is there something I've missed? Or am I just being very hopeful?

Oh, it's a recon 1.9dg that's done about 55000miles running and idling smoothly, last 20000miles on gas.

Post by **Mocki** » 25 Jan 2008, 18:31

you may well have a cracked head there.......

you really need to have a gas test on the coolant, it sounds like it may be forcing combustion gasses into the coolant.

head gaskets are not conventional on the wbx, and dont lead to water.
the water jacket seals however do lead to water loss, and air gain.

Post by **Westy.Club.Joker** » 25 Jan 2008, 18:38

My diesel was doing very similar things, turned out to be a cracked head. They can exibit some weird faults when there is a head or gasket problem, not obviously pointing to a specific thing, but your`s does sound like it`s the top end.

Whip the heads off and see what you find

Post by **Jamie25** » 25 Jan 2008, 18:46

Mocki - excuse my ignorance, but you really need to have a gas test on the coolant - what's one of those then?

Westy - I've seen a few people suggesting heads can be 'whipped' off, but reading the hanynes manual they suggest this is an engine out job. I guess because of the layout of the engine this can be done in situ???

Post by **Jamie25** » 25 Jan 2008, 18:50

Mocki, again excuse my ignorance, but having read up on the engine I thought I had a basic understanding of it. Is it not likely to be the head gasket or head if the combustion gasses are getting into the coolent, rather than the water seal seeping coolant then sucking in air from ambient when cooling?

Post by **Mocki** » 25 Jan 2008, 19:04

if the head gasket fails, you will loose compression, and maybe get combustion gasses in the coolant, but it wont do the common oily watery thing, is what i ment, the head gasket is just a compression sealing ring.

not explaining what i mean is common these days! lol

your problem sounds like its combustion gasses in the coolant, so having it "sniffed" would confirm the problem, if not the cause, you would then have to have the heads off, and it would confirm it isnt a air / coolant leak at fault.

be sure before, because if you take the heads off, you are going to be paying for a water jacket kit whatever...

Post by **Jamie25** » 25 Jan 2008, 19:12

Thanks Steve/Mocki, your adive is as always invaluable.

I assume any reputable garage can perform a 'sniff' test or is it something I can do?

Post by **Westy.Club.Joker** » 25 Jan 2008, 19:52

It`s a specialist instrument, not some geezers nostrils mate

Heads will come off with the motor in situ, BUT be prepared (were you a boyscout?) for exhaust stud breakage

and also cylinder head stud probs

which usually means an engine-out job to sort. Don`t get to stressed over it, it`s not a MASSIVE job to whip the engine out

Post by **Jamie25** » 25 Jan 2008, 19:58

My friend has a police dog - thought they might be able to do the sniff test

Exhaust studs should be fine as I changed the entire system a few months back and gave the studs some copper grease. Knowing my luck though the head studs will cause problems so I'll plan for the worst!

Post by **Titus A Duxass** » 26 Jan 2008, 08:21

That's exactly what mine was doing, it was a cracked head.

Post by **Laurie** » 05 Feb 2008, 11:09

Look through Cylinder head tools on fleabay and you'll see a tool that only costs 25 quid. It consists of a bottle of liquid that changes colour if there are exhaust gases in the water. Think the site is Tools n stuff, but not sure.

The DG objects strongly to being overheated and it will often blow the head to barrel seals. Running without thermostat can do the same!

Engine out is best. Check for rust in studs if you do it yourself, or, if you replace, make sure that all head studs are new.