Overheated and Now...

**bowlink** · 22nd February 2023, 07:25 AM

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** · 22nd February 2023, 10:29 AM

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** · 22nd February 2023, 06:39 PM

Originally Posted by 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.

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** · 23rd February 2023, 03:47 PM

Originally Posted by BradC

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** · 27th February 2023, 03:56 PM

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** · 28th February 2023, 05:45 PM

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** · 28th February 2023, 08:28 PM

Originally Posted by 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…

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** · 27th March 2023, 05:52 AM

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** · 27th March 2023, 08:48 AM

Originally Posted by bowlink

Now to figure out which bank blew its gasket…

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

**bowlink** · 16th April 2023, 08:00 AM

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

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