Thread: Overheated 3.9 V8

Driving any engine with no coolant generally results in a bad ending. Pat

G,day mate I would say you may of hit the nail on the head. Blown head gasket. I did one not so long ago and the car took a bit of winding over before she would fire up. Run ruff for abit than seemed to run fine. This was when it first started playing up. After 2-3 weeks of driving it like this I could'nt keep the water up to it she was blowing more steam than a steam train. In all this time there was'nt a drop of water in the oil. ( I was'nt going to say this every one will think im mad) I drove to Brisbane and back from Newcastle filling the water 3-4 times between fuel stops. Goes to show the 3.9s are a strong engine

Originally Posted by The Brun

G,day mate I would say you may of hit the nail on the head. Blown head gasket. I did one not so long ago and the car took a bit of winding over before she would fire up. Run ruff for abit than seemed to run fine. This was when it first started playing up. After 2-3 weeks of driving it like this I could'nt keep the water up to it she was blowing more steam than a steam train. In all this time there was'nt a drop of water in the oil. ( I was'nt going to say this every one will think im mad) I drove to Brisbane and back from Newcastle filling the water 3-4 times between fuel stops. Goes to show the 3.9s are a strong engine

haha, I drove 1600km with slipped liner from Sydney to Rocky. used 6 litres of coolant lol.

No worries thought it might be the case

No water in the oil with this one as well

Jock ...

The spark plugs might of just got fried from being overheated .... Pull out the plugs and check for any that have been steam cleaned

If all are black in colour ... Then just try a new set

Cheers
Mike

So if it were the head gasket you would expect a head gasket kit (approx. $240), possibly shaving the heads? ($200) and manifold gaskets. Anything else that could be an issue? Apart from a slipped liner

Or could be just spark plugs

Like all repairs Jock,do the simple things first. Pat

Hi Jock
I would strongly suggest pulling out the plugs and checking their appearance. Black sooty is normal running rich, cleans easily. Baked on crud, probably oil burning. Will be black and wet with oil if fouled up completely. Could be a broken compression ring.

Operate the engine for max. 30 seconds from cold. Do not rev it. Remove plugs. If there are coolant coloured drops on a plug, or rust, you have a problem. The last 3.9 I worked on with this problem wasn't fixed by changing either the heads or the gaskets. As a 3.9 it is likely the block is cracked. My customer then put some heavy duty stop-leak into the cooling system and is still driving it as he can't afford a new engine. That was 3 months ago.

Then check the coolant. If it's full don't lift the heads just yet. Do a compression test, all plugs out and throttle wide open. You are looking for evenness rather than amount. A loss of 20psi is a sign of 1 broken ring. More loss is likely from a missing gasket section or burnt valve. Squirting oil in to the cylinder for a wet compression test will raise the compression if it is a broken ring.

Lift the oil filler cap and look for white sludge. This indicates water in the oil. A small amount in winter is normal, enough to look like custard dessert is water in sump. It is rare for the head gaskets on V8's to fail into the water jacket but not unknown. Sometimes all you need is new composite head gaskets instead of the shim steel ones. A cracked head will do this too. Generally cracks are more likely on the middle two cylinders, and head gasket water leaks on the end cylinders.

Skimming the heads is a waste of time unless they are showing signs of warpage, usually fire rings move and leave a groove. Use a straight edge and check for surface flatness in every direction. You are wanting 0.002" or less in any direction.

Best of luck, just do as much diagnostic as you can before you dismantle. Spoken by one who has been caught recently.