GQ hiding coolant

[jimmyjam]

G'day all,

I've got a GQ with the 2.8 turbo diesel, safari snorkel and intercooler.

Last year it did a head gasket and so it was crack tested, machined, new gasket, new thermostat, new timing belt new fan belts and new water pump.

It's now hiding coolant. I say "hiding" as between the mechanic an me we can't figure out where it goes!

If I fill the cooling system (with the heater on and using the 2 breathers) and then take it for a drive, it will lose as much as 1 litre on a 70k round trip....
It's not filling the pistons as it starts easily and there's no excessive steam from the exhaust on start up.
It's not ending up on the floor of the shed.
It's not ending up in the cabin from the heater.
It's not in the oil.
I'm getting little airbubbles in the overflow after I stop the engine sometimes too.


It's running fine and not overheating, however I'm not sure what would happen on long trips. I'm really sick of refilling that (stupidly designed) cooling system...

any ideas?

Thanks

[97_gq_lwb]

These systems are a bastard to bleed the air out of.
But if you have air bubbles coming out into the overflow after all this time that is a sure sign of a compression leak into the cooling system.
It will usually force the coolant into the overflow then the overflow will let it run out.

[jimmyjam]

I don't really feel like redoing the head, so I checked for a compression leak with an upturned plastic bottle of water in the radiator inlet. No air bubbles when blipping the throttle.... Unless it's only once it gets warm enough? I'm considering some stop leak (clog everything) additive to see if it makes a difference?

[97_gq_lwb]

These additives usually do more damage then good they clog up the radiator etc and are really only good in emergency situations and i highly doubt it will work on a compression leak..
Generally an rd28 cracks the head on number 5 cylinder they are hairline cracks.
My advice would be take it to natrad or a specialist with the right equipment that can test it properly .
I have seen other things cause similar issues.

[The Tank]

If your mechanic can't find a major leak like that it's a pretty simple fix.

1. Fire your dodgy mechanic.

2. Get a new mechanic, explain the situation and ask him to fix your ride.

Coolant doesn't just dissapear like that and a simple pressure test will find it every time...without fail...unless your mechanic is an idiot or thief or both.

It pays to not employ this technique in small towns without serious thought first and it helps if your new mechanic is not mates with the old one.

[Barney Rubble]

If your mechanic can't find a major leak like that it's a pretty simple fix.

1. Fire your dodgy mechanic.

2. Get a new mechanic, explain the situation and ask him to fix your ride.

Coolant doesn't just dissapear like that and a simple pressure test will find it every time...without fail...unless your mechanic is an idiot or thief or both.

It pays to not employ this technique in small towns without serious thought first and it helps if your new mechanic is not mates with the old one.

ROFL@the tank.

[Barney Rubble]

By the way i would certainly not use any of the stop leak type products unless its an emergency...

[HammerBuilder]

I had slightly different thing with my 2.8 round town never noticed anything no different levels in overflow no drips or bubbles but on a long trip out on the hyway n towing after bout 300k's it'd start slowly pumping water into overflow tank then I'd pump it back in with cap off n air compressor on low pressure through the overflow on the overflow bottle, do the same cruise round town for week or 2 then hyway do the same but if I just kept on 90km/hr it never pumped any thing.
Done the usual replace the cap with genuine & then thermostat & I even made a bleeding tube with old radiator cap n bit of inch pipe pump the coolant in clamp the overflow tube then crack the 2 bleed spots got all air out again & again
Finaly got jack of it n ripped the head off n found with the multi layer gasket there were long cracks in 1 or 2 layers but not all so what I reckon was happening was with high boost the compression was going threw these into water jackets & pumping water out threw cap into overflow but there was no other signs of blown gasket no bubbles in radiator running hot or cold only when under full or high boost.
I was lucky I guess as I am second owner n this was first engine problem with 320,000 on the clock n no cracked head.
Done the gasket myself n now no high temps after long hyway with trailer n no real changes in bottle height of fluid YIPPEE On a winner

I also took my trol to many mechanics & they couldn't find the problem cause mine was showing no signs round town....
Just so glad all good now so many more trips I can do before I swap to 4.2TD Turbo more time to save to get a better system together

[jimmyjam]

Haven't been on this forum for ages!
For those interested it had done the head gasket again, but on the lower side just between the two middles cylinders.
When the mechanic (really good mechanic and top bloke) had the head off, he checked everything and found the top of the block was not completely flat, it had a low spot in the middle.
Machined the block, new head gasket and no dramas since.

[rkinsey]

Hi Jimmu,

I had the same issue in my wifes AUII Falcon. No cracked head, no leaking hoses. (Replaced them all anyway) new radiator, no water/coolant in the oil. Baffled me for months.

Then a mate of mine (who is a mechanic) said "Replace the radiator cap" - It couldnt be that simple....?!?!

I replaced the radiator cap and bigo, no more disapearing act for the coolant!!

Basically (as I understand it) is that preasure builds up in the system and any excess coolant flows into the overflow bottle. When the system cools it creats a vacum and sucks the coolant back into the radiator. If you have a doggy seal on the radiator cap, air gets in and it doesnt suck the coolant back.