Overheated and Now...

[bowlink]

Hi all, looking for some advice on what to check next.

I lent my '01 4.6 p38 to my brother and while towing a trailer with two dirtbikes up a gravel hill on a hot day the lower coolant hose blew (from water pump to thermostat). He happened to be looking at the temp gauge when it happened so he noticed the spike in temp and shut the car off straight away. Now, the engine heats up at a normal pace but continues to steadily rise to over 108oC before I switch it off.

Symptoms are:


Water is boiling in the expansion tank
Top radiator hose is hot and tight
Heater core pipes are hot
Heater is blowing cold (brother said he was able to feel hot air on the day but only when the radiator caps was removed, but I am unable to recreate that)
No hot air coming from heater
Bottom radiator hose warm/hot
Radiator warm/hot
Engine temp consistently climbs
A/C condenser fans come on
Viscous fan can be stopped by hand when engine is hot
Bubbles in the expansion tank coming from the small radiator hose that routes around the battery
Bubbles in the expansion tank coming from the bottom of the tank - smells suspiciously like exhaust/engine fumes


I have done/tested the following:


Removed and tested the thermostat and it opens as normal when boiling water is poured into/over it,
Switched expansion tank lid with a known working one,
Flushed heater core
Did a dry compression test with the following results:

165-170
150-155
160-165
155-160
150-155
145-150
145-150
155


Any ideas on what to test next?

[Tins]

Removed and tested the thermostat and it opens as normal when boiling water is poured into/over it,


Just an observation. That doesn't eliminate the thermostat. Better to put it into a pan filled with cold water, with a thermometer, and raise the temp on a stove. watch for the stat to start to open and check the temp. A lot of the symptoms you describe could be caused by the stat.

Air lock is my next guess.

( Trying really hard not to mention hg )

[shack]

The next step I guess would be removing the heads, hopefully not a slipped liner as well... But you can't really tell what's going on without pulling them.


Edit:

Sorry that's sounded a bit brusque.

An air lock is a possibility, but that will not explain the fumes in the header tank.

You can also buy test strips to test for Combustion gases in the coolant, if that comes back positive, see above.

[bowlink]

Worked on it most of the day today and managed to get all the air out which made the heater blow hot, although not consistently.

Everything was pointing towards a shut thermostat so instead of testing a potentially faulty one, I swapped it out with a known working one from my other p38. I thought this because the top of the radiator was still very hot to touch and the bottom was lukewarm when the nanocom said the engine temp was 120+oC. It didn't make a change unfortunately.
I also tried reverse flushing the radiator thinking maybe it was blocked but it was all clean so no issue there. The expansion tank's cap wasn't letting any pressure out whatsoever so again tried swapping it with a p38 that was running fine but no change.






I am going to get one of those sniffer tests that detect CO2 for the expansion tank. That will be a definitive answer for if there are exhaust gases in the system, so then just need to flip a coin and pick a bank to pull to bits for the head gasket

[350RRC]

Cross pollination from another thread............... could also be that the vanes on your water pump have rusted to nothing.

DL

[bowlink]

Interesting fault. It would explain a seemingly lack of circulation similar to a thermostat jamming shut. The RR has done 180kms and has only had two owners prior, the second having it for 15 years and servicing it regularly. The condition of the metal coolant pipes were good as well so I don't think that would be the cause. I like your thinking though

[ozscott]

Not hard to get to water pump. I would strip it off. Cheers

[bowlink]

True, it’s worth checking while I wait for the CO2 sniffer to arrive. I’ve previously tried getting the fan off and it was nothing short of tight, so I’ll give it a good crack and see what I find

[PeterH]

Did you properly bleed all the air out of the system?
That would be my first step, sounds like air in system to me.
Also, if you can stop the fan by hand, you need a new viscous fan hub, that could have been the cause of overheating in the first place.

[zzsteve]

With heater blowing cold and temperature rising, maybe this points to poor coolant circulation, so - air lock, corroded impellor or blocked radiator. Blocked radiator might explain the blown lower hose. You might get a view of a few channels up through the drainage bung, but at that age it is probably up for a replacement, particularly if investing in a head recon job. Just a thought.
HTH
Steve
'97 HSE

[bowlink]

A little update on where I am at:


I took the water pump off to check it and everything is working fine which was a little disappointing but nevertheless it is one more thing I can cross off the list.
I'm going to refill and thoroughly bleed the coolant system after putting the water pump back together and if that doesn't change things then it will be on to using the sniffer kit that has now arrived.

[DieselLSE]

Sorry to come into this so late, but the P38 is notorious for blocked radiators. They often appear to be flowing OK, but when checked are at least 30-50% blocked. Either get it flushed or replaced.
The late Ray Allford from Romsey British Automotive would religiously service or replace his radiator each year! When I purchased my P38 (sight unseen) in Auckland, the mechanic who had been servicing it for the previous owner advised the radiator was fine. I insisted he get it serviced and he was surprised when he reported back to me that it was 30% blocked.
In any event, I would be surprised if there wasn't damage to the heads or liners. Good luck.

[BradC]

Sorry to come into this so late, but the P38 is notorious for blocked radiators. They often appear to be flowing OK, but when checked are at least 30-50% blocked.

Holy crap! What's blocking them? It can only be either material stripped from other parts of the cooling system, or some form of chemical deposit from the coolant. There's nowhere else for solids to come from.

[DieselLSE]

Holy crap! What's blocking them? It can only be either material stripped from other parts of the cooling system, or some form of chemical deposit from the coolant. There's nowhere else for solids to come from.
As I understand it, it's from the coolant. Perhaps due to not being changed every couple of years which was the standard back then. Dunno. But the under specced radiator restricting flow has led to the demise of most of the damaged 4.0 and 4.6 V8s. The odd porous head casting (also a 3.9 issue), slipping liners and, of course, willful neglect will have a few tallies on the board, but the winner will be the radiator.

[Hoges]

Had the blockage problem in my P38. I replaced the radiator and started using deionised water 50-50 / GM Delco coolant (for their aluminium LSxx V8). Replaced every 24 months. No further problems over the following 5 yrs.

[bowlink]

So after reassembling the waterpump and bleeding the system (to no avail) I managed to use the CO2 sniffer. The results were very conclusive and showed there was CO2 in the coolant. Bugger.

Now to figure out which bank blew its gasket…

[Hoges]

So after reassembling the waterpump and bleeding the system (to no avail) I managed to use the CO2 sniffer. The results were very conclusive and showed there was CO2 in the coolant. Bugger.

Now to figure out which bank blew its gasket…

Do both heads, and while you're at it, have a close look at the camshaft. The lobes are notoriously soft. They can deteriorate between 100-150k km if the oil changes have not been properly maintained. It's possible to remove the cam without removing the engine, a bit tricky...take out the radiator and move the oil cooler and aircon heat exchanger etc out of the way. Search this forum...I posted photos and a write-up on same around 2013/14.

[ozscott]

I would do both heads and get them crack detected, refaced, valves and seats cleaned up, new valve stem seals. Check block faces with straight edge. Thoroughly clean block face. Reassemble using stock LR Elring made in Germany gaskets and ARP head studs (they do a kit for your motor) and new radiator while there. If she drove well and had a good service history then cam probably ok. Cheers

[Tins]

Now to figure out which bank blew its gasket…

Doesn't matter. Do 'em both as already said.

[bowlink]

Update: still overheating.


I have redone both headgaskets and got the heads skimmed down a bit. Put it all back together and fired it up............only for it to overheat again in the exact same way. The least to say it was very disheartening. I think what has happened is 1) the viscous fan has given up causing a lack of cooling, 2) something else in the cooling system failed, 3) this has then caused the head gasket/s to fail.


The top hose is hot hot hot as is the top of the radiator, the heater hoses are hot in and warm out, the small hose going to the thermostat is hot hot hot, all other small hoses are hot including the hoses to the throttle body, and the hose from the thermostat to the radiator is cold/luke warm with the lower radiator being cold.


Recap on what I have done:


Swapped thermostat out with a working one
Checked waterpump operation
Replaced headgasket
Bled the system too many times to count
Flushed heat core both ways with a garden hose
Reverse flushed radiator with a garden hose
Swapped expansion tank cap with a working one
There has been no evidence of sealant or leak-blocker in the system when inspecting the thermostat, waterpump, and waterways.

Question: When bleeding the system and you remove the bleed hose from the top radiator, does the fluid coming out of the bleed pipe exit the hose fully or "jet" out half the hose? The fluid currently comes out the bleed pipe in a semi circle and does not fill the exit pipe (comes out in a "D" shape rather than a "O" shape). I hope this makes sense!


A big shout out to PaulP38A's step-by-step guide for the headgasket replacement, it made things so so much easier! Here's the link for anyone else: Engine Refresh (top end) | PaulP38A.com (https://paulp38a.com/range-rover-p38/engine-refresh/)

[Ronski]

To keep it simple.
At the beginning you said that you could stop thermo fan by hand when hot.
It is buggered.
Reverse flushing the radiator with garden hose, not very effective. It needs the tanks removed and cores cleaned with rods.
You said, top hose very hot, bottom of radiator cold....it it blocked. sediment falls.
Had exactly same issue with old Jaguar radiator, top hot, bottom cold. I watched the guy at shop do it. Shocked that 1/3 of it was completely
blocked.