To pull head or not to pull head

Submitted: Friday, Feb 16, 2007 at 20:02

ThreadID: 42387 Views:7117 Replies:12 FollowUps:25

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GQ_TUFF

Ok Some of you would be familiar with this ongoing problem of mine, of my 2.8 GU spitting its coolant out of the overflow. I have had it at the mechanics last week and he admits there is a problem but he is not 100% sure if its a gasket or head as there is no bubbles when you rev it ect, and he says as the 2.8 runs 21-1 compression you would be pretty sure if you had done the head ect. Now this posses some questions.....I have being told by two sources that their cars displayed the same symptoms and that their problem was the water pump under certain loads actually sucked air in. I told this to a radiator guy and his responses was "bulldust" in 30 years never heard of that one and your friends must be lying....more confusion!!!!.......As you can imaging I want to be 110% sure that its the gasket or head before I commit to this job.

So this is what it does

After a run above 100 km/h about 2800 rpm it starts pushing the coolant across, to the point of filling the overflow and then some, after about 200 kms I have lost 2-2.5 litres.
It won't recover what it pushes over, mechanic reckons it pressure tested normal cold and warm. (yes has a new quality cap)
But around town ie: nothing over 80 km/h no issue, run for 1000 kms and not use a drop???
It isn't showing any oil and water mix and no moisture in the exhaust or rough running when cold or hot.
It has no external leaks that I can find and trust me I have looked and looked.

I have being told by several mechanics that there is no test for exhaust gas in coolant for a diesel???? I am sure I have heard it mentioned here before.

So please any opinions would be great, or anybody know of some tests that can be done to help the problem be found correctly?

I am putting it on a dyno tomorrow to see if we can see whats happening as it happens as opposed to when it has happened. Apart from that I am stuffed if I know

Any help will be greatly appreciated

Cheers Stefan

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Reply By: Gob & Denny - Friday, Feb 16, 2007 at 20:11

Reply By: On Patrol - Friday, Feb 16, 2007 at 20:22

Friday, Feb 16, 2007 at 20:22

As discussed on the phone Stefan, my money is on the water pump seal, allowing air in when cooling and preventing coolant to suck back into the system.

Others will / may disagree but thats OK, you will get a range of ideas presented.

Good luck with the Dyno tests tomorrow.
On Patrol

AnswerID: 222165

Follow Up By: GQ_TUFF - Friday, Feb 16, 2007 at 20:29

Friday, Feb 16, 2007 at 20:29

Well, Its $100 for a pump, and $3500-$4000 to do The top end....I'll give you one guess which I will try first!! If the dyno test leads me to the smaller one....Whats your garage space doing tomorrow???? LOL

FollowupID: 482977

Follow Up By: On Patrol - Friday, Feb 16, 2007 at 20:36

Friday, Feb 16, 2007 at 20:36

It would have to be the car port Stefan, youve seen my garage!!!!

FollowupID: 482982

Follow Up By: Member - DOZER- Friday, Feb 16, 2007 at 20:40

Friday, Feb 16, 2007 at 20:40

Question...is your 2.8 alloy headed?? Either way, u can try this first if you like.....try tightening down the head bolts, by backing off a quarter turn one at a time then retensioning. Make sure the motor is comd and the rad cap is off/system depressurised,
The water pump does not explain the water being forced out of the system when running....for this to happen, something pretty powerful is forcing air into the system...yes, i think you need to renew the head gasket. It holds back 2500psi at cranking speeds, all it takes is a bit of hard work to get things nice and hot, and to allow a bit of compression past the gasket into the water gallery (remember, at 100km/hr you have a turbo forcing in the air at full boost b4 it gets compressed, so this is where the most pressure and heat is seen in the cylinders....) which are right next to the water galleries.....)
Id be driving round with the cap on the first notch to let the compression out b4 u blow a hose....top it up each morning, run the water level juast above the core.
Andrew

FollowupID: 482984

Follow Up By: On Patrol - Friday, Feb 16, 2007 at 20:50

Friday, Feb 16, 2007 at 20:50

G'day Dozer
Your theory is sound mate, but how do you explain the water not sucking back into the system at cool down, it just remains there. Would the head gasket cause that???

This is a puzzle in its self as to why the coolant will not return to the system at cool down, could there be a residual counter pressure of air when cool?
On Patrol.

FollowupID: 482989

Follow Up By: GQ_TUFF - Friday, Feb 16, 2007 at 21:35

Friday, Feb 16, 2007 at 21:35

Thanks for that Dozer, Funny about your theroy of letting some pressure out, today I ran a little test....after it let out around 2 LT, it seemed to almost stop doing it???? It has a 12.7 LT capacity so it was running at around 87% capacity and it sucked coolant back from the overflow bottle to around the MAX fill line. Its like things sort of equalised. As I have being topping up at every possible time, is it possible to over fill the system? I have being filling up the radiator and header tank to the very top and the overflow to the MIN mark.

Cheers Stefan

FollowupID: 483002

Follow Up By: Member - DOZER- Friday, Feb 16, 2007 at 23:20

Friday, Feb 16, 2007 at 23:20

The system is supposed to work by firstly, having no air in it, secondly letting water out past the cap when it expands due to heat, (and still maintain 0.9 bar in the system) and when it cools, the vacuum caused by contracting water as it cools down sucks it back in via the cap. When pressurised air is introduced, it pumps out the water, leaves air in the top tank, and when the water cools, there is not enough suction to overcome the air space left in the top tank and suck the water back. Andrew

FollowupID: 483026

Follow Up By: Member - Davoe (Nullagine) - Saturday, Feb 17, 2007 at 15:35

Saturday, Feb 17, 2007 at 15:35

Unless i m mistaken 2.8s are renowned for cracking heads. Alot of the Brunswick v8s are in former 2.8s for this reason. By all means look for a cheap fix but experience has shownme if it looks like dog bleep e and smells like dog bleep e then....................Is probably dog bleep e

FollowupID: 483136

Follow Up By: Danny & June - Saturday, Feb 17, 2007 at 17:59

Saturday, Feb 17, 2007 at 17:59

Try the Thermostat

FollowupID: 483166

Reply By: Member - Davoe (Nullagine) - Friday, Feb 16, 2007 at 20:29

Reply By: mrbasilbrush - Friday, Feb 16, 2007 at 21:07

Reply By: samsgoneagain - Friday, Feb 16, 2007 at 21:10

Reply By: Member - andrew B (Kununurra) - Friday, Feb 16, 2007 at 21:17

Friday, Feb 16, 2007 at 21:17

Gday Stefan

Funnily (not) enough I am in exactly the same position......chemiweld seems to have done the trick, but I have noticed a few bubbles here and there...I'll know a little more on the next run to work. Mine got a negative test for CO2 - so the bubbles weren't exhaust gas......I can't see how the waterpump could draw air in at over 9psi (radiator cap pressure). I think the turbo is watercoled....I think these little engines run about 12 psi, so a suspect seal in the turbo could theoretically put 3 psi into the coolant (if all the planets are in line etc.....) I, like you, am at a bit of a loss as to what the problem is, I will probably look at the water pump first, doesn't hurt to change them now and then anyway - the last one I did was about halfway between the Berkley Roadhouse and Cammoweel on a stinkin hot december afternoon, but thats another story! I may consider another chemiweld dose, and re - torquing the head, but it won't be comeing off in my case.....

I have made my decision......when this one requires substantial money to be spent on either motor, gearbox, or even clutch, its Brunswicks here I come! (I can't handle Roachie and Bilbo having all the fun! I don't do that many k's anyway, so this may very well be the car to see me through the nest 20 years.......just do it "a piece from here and a piece from there"!

Good luck with your 2.8 adventures...pity we both have the same problem or I may have some parts for you....

Cheers Andrew

AnswerID: 222189

Follow Up By: GQ_TUFF - Friday, Feb 16, 2007 at 21:55

Friday, Feb 16, 2007 at 21:55

G'day again Mate, we always chat about the crap things!!! lol

I have being told they have single use head bolts so its off with the old and in with the new, Well RE water pump....its at 130000kms and still the original so for $100 why not??
Will have a look re water cooling the turbo, I havent considered that.
At what Stage does your low coolant alarm go off? As I mention in an earlier reply after it has lost no more than 2 LT.....It seems to settle down.....but is 2 LT danger zone?
I am really hoping to find out on the dyno tomorrow what is happening at high load, Plan to run it at 130 km/h for at least 1/2 an hour and see what happens.
will keep you posted, why is it you can get the gas (co2) test where all the mechanics here reckon they cant do it on diesels???

Fingers crossed!!!
I would love to do the chev thing, but I would have to get divorced first I reckon, sold my soul to get this car would have no chance of convincing SWMBO that another 25k is a good idea!!!

Cheers Stefan

FollowupID: 483006

Follow Up By: Member - andrew B (Kununurra) - Friday, Feb 16, 2007 at 22:11

Friday, Feb 16, 2007 at 22:11

Its all good isn't it.....Last time I had a head problem I witnessed the test - the water in the test kit (its a bit like a hydrometer) went bright green, indicating CO2, a few squeezes in the open air (oxygenated) the liquid went clear. It was repeated in front of my eyes, so it can work. This time, no co2 (performed by the same mechanic). The mechanics may be eluding to the possibility of a diesel squeezing the gas into the water prior to ignition, with the diesels higher compression ratio, but I doub tthis would be the case. It will be interesting to hear about your dyno results...mine went from 84 to 96 kw with the gas, but to have an accurae comparison the;y would have to be done on the same dyno strait after one another.

There won't be a divorce over the V8, if and when it comes about....I get away with a fair bit really. I compare that with a $50K changeover to the last run out of the real 4wds and I can have a win...sort of. These 2.8 problems would be OK if they were a simple motor with cheap(ish) parts, but everything costs thousands. I liked my old MQ, even though SD 33 parts wern't exactly cheap, there was a few available from wreckers etc fairly cheap and simple to fit (new engine in a day)

Look forward to your results tomorrow.

Cheers Andrew

FollowupID: 483008

Follow Up By: Member - andrew B (Kununurra) - Friday, Feb 16, 2007 at 22:18

Friday, Feb 16, 2007 at 22:18

Forgot to add, my coolant sensor is a bolt that is about 35 mmlong through the radiator cap (on the radiator, not the plastic tank above the overflow), so as son as that level drops about 35 ml, it beeps away, which is usually about 2 litres or so to add. I am very reluctant to let it get lower than this, as I have heard somewhere that these engines crack heads and do head gaskets if you give them half a chance.lol......sort of.....the $150 odd I spent on this little sensor is great piece of mind, and I will never own a 4wd without one now.