Overheated 3.9 engine

[David Wright]

This afternoon whilst out the engine (3.9 on gas) just died, loosing cylinder after cylinder until it came to a full stop. Upon inspection the upper water hose had split and all collant had been lost and no temp rise on the gauge.

My immediate reaction was that one or both head gaskets had gone(these are composite gaskets fitted some 3 years ago) after a compression test using a Gunson tester all 8 compressions were in the green indicating 105 -120 psi.

This suggests to me that the gaskets are OK is this likely to be the case? and if so where else should I start to look for the problem

[Bowie69]

105-120PSI seems rather low TBH, what sort of mileage has it done?

[David Wright]

Probably about 5000 miles

[Bowie69]

Since rebuild or since HG change? If the former then they still strike me as rather low...

[David Wright]

Since a complete rebuild

[Bowie69]

Test compression figures are as following for the 3.9:8.13:1 150-160 PSI9.35:1 170-180 PSITry some oil in the bore and retest....

[David Wright]

Tried that and pressures now around 165 psi but several of the cylinders take three strokes to get up there - is this acceptable?

The engine is a 9.35 CR

[landy V8]

thats about what it takes to get the pressure up.may need a rebore or new rings.doubt it would be head gaskets on both banks.

[David Wright]

If it needed a rebore or rings would that not affect the compression?

[landy V8]

yes it would.by adding oil to the bore and then doing the compression test you can tell if it needs a rebore or rings.the compression figures you quoted have increased after adding oil which indicates to maybe rings or rebore.

give the guys at "V8 Developments" a call and they should help you out.01775750000

i've used them for all my bits when i rebuilt my 3.9.

[p76rangie]

Seeing that the motor is not running, I assume that you are doing the compression tests cold. If so, the figures do not mean much outside it still has enough compression to run. So fire it up and then re-test.

[Cynic-al]

mine was still running with some of the cylinders under 50psi, she smoked a lot so i think the engine oil was helping to seal them

Maybe the hose was just weak? Or the pressure built up for another reason? I'd repair it and try it again before stripping the engine down. Just don't stand looking over the engine when you test it for the first time

[Bowie69]

Sounds like you may have got away with it, just to save any further confusion, compression tests should always be done HOT.

Have you had it running?

Maybe the split hose was just that, a split hose.... and the reason it stopped running was not an over heat, but the LPG vapouriser freezing up and not supplying any more fuel to the engine.

Fire it up and go drive, you got two chances 

[Range Rover Blues]

Any damage is done now so you might as well get it running and see. One big problem with overheated rover V8s is that the cyclinder liner can separate from the deck, the golden figure is 3 overheats to crack the block. This cuases the fabled porous block syndrome.

[David Wright]

Well I followed your advice and got it started with a new distributor cap and leads and it is running well so it seems that I have got away with it. I have of course discovered one of the built in safety features of the V8 in that if the top hose splits water pours over the distributor and shuts down the engine before it can overheat - now wasn't that a clever design!!

Thank you very much for all your help, advice and encouragement

[burn_e]

if the top hose splits water pours over the distributor and shuts down the engine before it can overheat - now wasn't that a clever design!!