Thread: 3.9L V8 on heat - is this normal?

Fwiw, the Earth is on the rear of the pass. side bank & faces the firewall. A bit tricky to get at, but can be done.

Id be suspect of the water pump as the hoses shouldnt be much different temps from eachother.

The water temp should be around the 90 deg C in normal operation but this can change with different radiator cap pressures and not so much at operating temp but thermostats.

The thermostat may not be opening enough or could be semi blocked by rust and gunk or water pump inlet/outlet the same.

You really need to put a decent guage on it and find out what it's getting to as these engines dont like heat being Alloy blocks and cast sleeves.

Do a bit of poking around, replace the thermostat and check water pump flow but make sure you bleed the cooling system to avoid getting air locks.

It does sound hot but without putting a guage on it you wont know for sure.

Originally Posted by 4bee

Fwiw, the Earth is on the rear of the pass. side bank & faces the firewall. A bit tricky to get at, but can be done.

Yeah thanx,

Have been reluctant to dig through the wiring...

...now I have no excuse...

...at the very least I know where to dig

Originally Posted by mcrover

Id be suspect of the water pump as the hoses shouldnt be much different temps from eachother.

The water temp should be around the 90 deg C in normal operation but this can change with different radiator cap pressures and not so much at operating temp but thermostats.

The thermostat may not be opening enough or could be semi blocked by rust and gunk or water pump inlet/outlet the same.

You really need to put a decent guage on it and find out what it's getting to as these engines dont like heat being Alloy blocks and cast sleeves.

Do a bit of poking around, replace the thermostat and check water pump flow but make sure you bleed the cooling system to avoid getting air locks.

It does sound hot but without putting a guage on it you wont know for sure.

How would I test for flow, or aternatively, what should I look for in a faulty water pump. Everything looks and sounds normal.

cheers

I do not know what temp it should be, but below is what happenned to mine due to excessive heat. Not sure whether by me, but more than likely the previous owner - the head had been off before, but i don't think they were aware that the block had lost its hardness so it was only a matter of time before it went pear shaped again - refer below

if your system is under very high pressure, you may have a blown head gasket - my engine is in the process of being rebuilt due to this, problem is if it gets too hot you actually destroy the motor, that is the aluminium can loose its hardness

Have you had any issue with loosing water? And if the motor has gotten hot then it is highly likely that the radiator will be full again from all the stuff out of the motor.

The motor in mine had been tuned and the advice i was given is that its within tolerances, but i didn't think it was right, so they checked it again - same result - within tolerances. Head Gasket at no 8 was leaking into the cylinder causing the compression to be greater rather than less therefore the computer didn't picked this up. 5 liners had movement, 9 valves weren't sealing, cam stuffed and anything alloy was warped

So end result of mine, new pistons, new cam....oh and the block had to be heat treated twice to get back to the correct hardness

Will get it back on the road sometime, hopefully before xmas cause were going to Fraser

Is it keeping water?? or it runs hot, then spews out from the cap, when switched off or still running?

Originally Posted by Offender90

How would I test for flow, or aternatively, what should I look for in a faulty water pump. Everything looks and sounds normal.

cheers

When you take the thermostat out is the best time to do it, whack the cover back on and top up with water, up to the top of the rad core, then run the engine and see if the water flows fairly fast or not.

That is crude but gives you an idea but not much, the only other way I have seen and used was a special test kit that has a site glass in it so you can see if the water is flowing and also has test ports on it to check pressure and temp etc.

Im not entirely sure where it came from, it may have been Snap on or Wurth as it was very good quality.



But the main thing is if there is a big difference between top and bottom hose temps

in my v8 110, i had water pump problems, pin hole in the rear of the pump housing which is also the timing cover. when i took the pump off, i found some of the vanes of the pump were eaten away by corrosion. this can happen to different degrees.
BTW, i fixed the hole by rebuilding the rear face of the pump housing with devcon, for those that don't know, it is a metalised epoxy compound which is great for high temp applications. this not only fixed the hole, but because it was "machined" while soft by turning the pump by hand, the tolerance between the pump impeller and the pump face was greatly improved, and made the pump much more efficient.
later, when i was fitting my 4L, we put a new radiator in and for some reason, we'd left the thermostat out. we found that the cooling system was working so well that without the thermostat, the engine wouldn't reach a happy operating temp.