Dodging The P38A Overheating Bullet (I hope)

[DieselLSE]

Had a worrying call from a new P38A owner yesterday: the car (1999 Gems 4.6) had overheated and the engine wouldn't start immediately after the event. Made a clicking sound like having a flat battery. Later they were able to put in about 4L of water and start the car but it wasn't running very well. What should they do?
I said I would come over and have a look and was wondering how I would tell two newlyweds with their recently purchased (for $9k) Rangie that either the motor had seized or the heads had been cooked or a liner or two had shifted or possibly all three and that they'd probably need a new motor.
It got worse as I needed to put in another litre or so of water and, satisfied that nothing was leaking out, got them to start the car. It sort of ran OK but appeared to be a cylinder down and was making a clicking sound that sort of sounded like a sticking hydraulic lifter, but not quite; or perhaps it was a liner working loose, but again, not quite. Perhaps it was a MAF issue. In any event, poor running was an nth order issue. What damage had the overheating caused?
As the motor was warming up, I poked around a bit. Hang on, what's that spark? A rubber cover had worked loose at the coil block and, sure enough, a shorting spark could be seen clicking away in perfect time with the missing cylinder. Stop motor, secure rubber cover, start motor, running perfectly. Young man thought I was a genius, but I felt like a goose for not picking it up sooner.
Motor warmed up and the gauge held a constant temperature. I had been worried as to where all the water had gone. But then I noticed a leak at one of the temp sensors. It had worked loose and was letting water escape under pressure. Tightened that and could not find any sign of leakage anywhere else.
As the temperature gauge was happily sitting where it should and the motor was sounding as good as any 4.6 I've ever heard, I suggested they drive around for half an hour or so keeping a keen eye on the gauge and stop immediately if it moved even a smidgen higher than normal.
They called me later in the day to say all was well. They're bringing it over tomorrow and I'll remove the radiator and have it flushed or replaced as necessary and show the young man how to do a basic service.
But I reckon, as things stand, they may well have dodged the P38A overheating bullet.

[DieselLSE]

Rangie was driven to my place yesterday and the cooling system drained, flushed and refilled. Radiator looked new and there was no gunk flushed out. BUT, upon warming up after the re-fill there were tiny bubbles (about half a dozen at any one time) appearing in the header tank. At first I was hoping they were just air pockets being forced out, but they appeared a bit too consistently for that and now I'm wondering if combustion gasses aren't finding their way into the coolant system.
I think a trip to my favourite mechanic for a pressure/combustion gas check will be next.

[trout1105]

Rangie was driven to my place yesterday and the cooling system drained, flushed and refilled. Radiator looked new and there was no gunk flushed out. BUT, upon warming up after the re-fill there were tiny bubbles (about half a dozen at any one time) appearing in the header tank. At first I was hoping they were just air pockets being forced out, but they appeared a bit too consistently for that and now I'm wondering if combustion gasses aren't finding their way into the coolant system.
I think a trip to my favourite mechanic for a pressure/combustion gas check will be next.

This sounds suspiciously like a blown head gasket [bigsad]

[PeterH]

Could be a head gasket, but I have found even after refilling the system properly and bleeding the air out, it can still take a day or two of driving to fully remove all the air.
The expansion tank will need a top up for a day or two, then it seems to be fine after that.
I have seen head gasket symptoms with the cooling system being pressurised and bubbles entering the expansion tank, (which was indeed a blown head gasket), but the bubbles entering the tank were constant, not in bursts like you are describing.
I would give it a couple of days and see if the bubbles persist and monitor the coolant level.

[banarcus]

When my wife boiled ours, both head gaskets failed at the rearest most cylinder on each bank. This cause quite a violent rumbling in the header tank, there was no mistaking about a blown head gasket with this. In your case, I'd wait a little while longer for the air to totally escape from the system via the small bubbles before any second guessing. Hopefully all is well for the newlyweds.

[trout1105]

If the engine got that hot the starter motor wouldn't spin then the odds of the head gasket/gaskets being fried are pretty high.
A simple "gas sniff" for hydrocarbons will tell if the gaskets are buggered and most workshops have the gas testing equipment.
Hoping that after the engine has boiled like this that everything is "hunky dory" if a forlorn hope, Ask me how I know [bigwhistle]

[DieselLSE]

If the engine got that hot the starter motor wouldn't spin...

The problem is I'm not really sure what happened. The description I gave was what I had gleaned from hubby as wifey was ill. So he's interpreted what she told him and as neither have a clue about cars I'm really flying blind apart from what I can observe. So, just the facts, Ma'am: Engine has lost coolant over time due to a loose temp sender unit; engine now runs fine except for suspicious tiny bubbles in expansion tank. BTW, the engine bay didn't smell as though it had been overheated.
Apparently, wifey was driving the car on a very hot day and when she stopped at the lights the engine stalled and would not start again until much later when it had cooled down. At some point wifey noticed the temp gauge was high (but whether that means a bit high or in the red I don't know). The car was driven a short distance home and hubby filled it with "about four litres" of water, but I don't think he was taking much notice of the volume.
Now you all know as much as I do!
Wifey will be coming over on Saturday, so I may get some better intel, but then again, perhaps not!
My gut feel at this stage is that either or both head gaskets have been compromised. If the bubbles are still there on Saturday, I'll get it pressure/gas tested. As for what happens next, I'm not sure. Replacing head gaskets is no biggie, but I'm worried that if I start looking for trouble, I'm sure to find it.

[Keithy P38]

These engines take a few goes to bleed properly. You need to allow the thermostat to open and fluctuate the revs quite a bit, around the 2000rpm mark, to do it properly. Just idling with the expansion tank cap off doesn’t cut it on a P38 haha! Could still be air pockets in the heads.

Cheers
Keithy

[trout1105]

Normally if the temp gauge shows in the red it is usually too late unfortunately and the not starting again until the engine had cooled is worrying.

[DieselLSE]

These engines take a few goes to bleed properly. You need to allow the thermostat to open and fluctuate the revs quite a bit, around the 2000rpm mark, to do it properly. Just idling with the expansion tank cap off doesn’t cut it on a P38 haha! Could still be air pockets in the heads.

Cheers
Keithy
Yes. I did that Keithy. But I agree I need to let them drive it around for a few days. I've advised hubby how to check and top up if necessary. But those bubbles are haunting me...

[DieselLSE]

Still haven't been able to speak directly to wifey, but hubby brought car over yesterday. It had been driven for a few days, including a trip to Geelong and the coolant had been topped up as there was still a slight leak from the sender unit.
I immediately checked the expansion tank, but nary a bubble could be found. I declared the motor healthy then and there. When the motor had cooled down I fitted a copper washer under the sensor unit and hubby has since advised that the leakage appears to have stopped.
So what really happened?
Hubby wondered if the stalled motor was caused by the recently fitted breathalyzer ignition immobilizer thingy. You know, the one you have to breath into to start the car. Apparently it is not unknown for them to falsely cut off the ignition. Perhaps the motor was starting to overheat and when the car was idling at the lights, the immobilizer falsely cut the ignition. Perhaps then wifey, trying to figure out what happened and wondering why the car wouldn't start (that would account for the clicking noise), noticed the climbing temperature gauge and wisely let the car cool down. Remember, it was a very hot day, 35 or so degrees from memory. It could be that the rising temperature gauge was only reflecting the temp of the stationary motor.
I think the engine survived the massive loss of coolant because the cooling system was in perfect condition and the motor had been previously overhauled very well. Whoever the previous mechanics were, I suspect they were very good.
So that's about it. I showed hubby how to do an oil and filter change and fit new pollen filters (they were missing!) and when they get back from their honeymoon I'll cover diffs and transmission etc.
But, gee! I still reckon they dodged a bullet...

[PeterH]

Thanks for the update, good to hear!
Cheers, Pete.