P38A cooling issue

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martynv8

martynv8

Well-Known Member
Posts
2,258
Location
Sheffield
Hi All,
Hope your all suitably stuffed & fed up of turkey by now.
So, I have a cooling issue since doing the head gaskets :
After re-filling / burping out any air etc it will idle / drive as normal. Engine warms up to operating temp in the usual time & needle stays at 12 0 clock.
However.....
After driving short distances (10 - 15 miles), i've noticed the engine smells hot. I put this down to assembly lube burning off at first but I also notice the top hoses are very hard. Also, the top of the rad is very hot but the bottom is cold as is the rad side of the thermostat. I put this down to a stuck closed thermostat so put in another (new). I did test both in a pan & they both opened & still have the same issue with the new stat fitted.
Flow seems ok - new metal impeller pump fitted 2 years ago.
Radiator seems to have good flow - 4 years old but only warm at the top half.
Don't seem to be losing any coolant. No suspect smells from the coolant.
Anyone had any experience of this, could it be rad, pump, airlock etc?
 
1. Radiator could be partly blocked allowing partial flow only (flow test appeared OK), the problem is you need to be able to feel the front of the radiator by hand to check for hot/cold spots and with the aircon in the way its hard.

2. Bottom hose could be internally delaminating allowing the inner surface to act as a flow shut off valve.

3. Try running the engine without a thermostat fitted.
 
zzr1200 said:
1. Radiator could be partly blocked allowing partial flow only (flow test appeared OK), the problem is you need to be able to feel the front of the radiator by hand to check for hot/cold spots and with the aircon in the way its hard.

2. Bottom hose could be internally delaminating allowing the inner surface to act as a flow shut off valve.

3. Try running the engine without a thermostat fitted.
Click to expand...

Thanks,
Will have another look at the rad & bottom hose. The rad did feel like the heat was equally getting cooler towards the bottom as if the lack of out flow was causing the hotter water to stay at the top of the rad.
PS, whats best way to run without thermostat, do I need to butcher my old one?
 
Martyn iv just replaced my rad due to a leak and it air locked as they do I had to reverse flush it to clear it by removing the heater matrix hoses one at a time inserting my garden hose and gently flushing it with the expansion cap off until it over flowed then removed the other heater hose and repeated, it was the only way to clear the air lock I then ran it with out the expansion cap on for 10mins just to be sure, also forgot I put the hose into the rad top hose as well until water ran out of the top rad hole then quickly fitted the rad hose.

Hope that helps mate
 
biketeacherdave said:
Martyn iv just replaced my rad due to a leak and it air locked as they do I had to reverse flush it to clear it by removing the heater matrix hoses one at a time inserting my garden hose and gently flushing it with the expansion cap off until it over flowed then removed the other heater hose and repeated, it was the only way to clear the air lock I then ran it with out the expansion cap on for 10mins just to be sure, also forgot I put the hose into the rad top hose as well until water ran out of the top rad hole then quickly fitted the rad hose.

Hope that helps mate
Click to expand...

Hi Mate,
I'll give the heater matrix pipes a flush through to get rid of any air locks there. I filled the rad from the top hose until it was coming out of both the bleed pipe on the rad & the return pipe from the lower intake so was sure of no air locks there. Ran without expansion cap on for 20 mins to get rid of any air. I didn't get the usual drop once the thermostat opens as previously though? Will try a drain again & do as you did though.
 
Long time ago I was given the task of replacing an engine in a Mini Metro from advice of an AA man... I didn't question it, just did it as I was strapped for cash. However, after replacing, it was flinging out water after boiling and the AA man again suggested the "new" engine must be knackered. I wasn't convinced though and decided to go against his advice. The old engine had shat it's pants and the oil had gathered in the radiator and clogged it something awful.

I got stuff to break it down (I forget what it was called, but it broke up the emulsified oil and I flushed it out with a garden hose) and cleared the rad. The car ran beautifully and did so for several years after that...

So I would be looking at the rad in you car as a starting point. If it's recent,clean it, if it's ancient, replace it. I need to replace George's rad is it leaks like a government department :rolleyes:
 
It took me 2 goes to clear the heater matrix so when I finally install my LPG I'm going to take my hot water feed off of the throttle heater pipes, its been by passed in the distant past by a previous owner and will hopefully insure no future problems with air locks at the matrix, I do check my fluids weekly tho.

I'm as sure as I can be its gonna be the matrix a good way is to see if both hoses are hot one of mine was getting hot the other didn't when I pulled the hose off the metal pipe it was bone dry, flush flush flush
 
Will give it a go this week Dave,
Both pipes feel hot...although i'm sure i'm getting a blast of cold air when cornering from somewhere, but with hand over central vent cornering all i get is hot air. :(
 
Do you have any issues with the torque converter locking up only at high temperature?
I had a defective coolant sensor, the one towards the rear of the head under the inlet manifold, that settled my temp gauge and now the lock us achieved sooner and stays on regardless of the temp reading! I also replaced the water pump, thermostat and filler cap. Everything has settled right down.
I hope there is an answer there for you?
 
Hi Mark,
My temp gauge works as it should so i'm assuming all is good with the sensor. Still seems odd that the engine seems hot but the gauge stays at 12 once warmed up. Would this explain a cold bottom of the rad though? No issues with torque converter to mention.
 
I've noticed on mine, that at first, before the therm' opens the engine will warm up and the top of the rad does get hot as the water is heated in the two top hoses but lower down the radiator stays cold unto the therm' opens. One test would be to remove the fan!! Start up from cold and access the water movement as it heats and opens the thermostat. You will get a hot rad top at first and then it should all heat as per usual. Then you have a good idea about the radiator circulation. With fan on you have no chance. I fitted an electric fan and removed the cowl from the radiator also. My temp gauge sits just below 12 90% of the time.
 
Try filling the system up with the engine running and make sure all the hoses around the top of the engine get hot, heater works etc.

Then do a block test, this will show any burnt gases in the system, so will eradicate possible cracks in the heads or failed head gasketry if it negative.

A laser temp reader is a boon for finding cold spots where airlocks are or if the rad has issues (by taking readings at random over the core), they are also very accurate. So one can find out the coolant flow temp before and after the rad.

I believe if I remember correctly that you had a top hatted block installed some while ago so the old slipped liner problem shouldn't arise.

I hope you get this resolved soon - the last thing anybody wants after a major repair job on an engine is hours spent with a watering can......
 
zzr1200 said:
If you need to pressure test the cooling system I have a pressure test kit. I'm only a short distance away and work in Sheffield during the week.
zzr
Click to expand...
Cheers fella, that's very kind.
I'm going to give it all a good flush through, check the rad & see how I get on with refilling tomorrow.
 
I have to say (and not to rub it in) we dropped the coolant from George around the end of November to re-fill with the red stuff... I digress.

We did it while changing the the winter tyres, so allowed it to run out of the rad drain plug, did the tyres & returned to it and re-filled it. Allowed it it heat up ad topped it up.

It was that simple. I did top it up with around half a litre when I got home, but that's been it since. I have noticed a slight drop in the level, but it's gently weeping from the rad so I'm planning a new one. It's lasted 17 years so can't complain :)
 
Hi, sorry to hijack the thread but I have similar probs, mine is the 2.5 weasel. with new rad all cooling pipes and recently replaced head gasket, head was skimmed ( cant remember by how much ) and pressure tested at same time. Tried bleeding as rave also by removing top overflow pipe ( rad to header tank) connecting clear pipe from rad and allowing to flow back into header tank. It will idle for ages and stay roughly at 12oclock on gauge move it 100yds and its straight into the red on gauge. A ll ideas welcome, many thanks.
 
Last edited:
Did you set the internal heater to full heat when topping up? Sometimes if the valve is closed, there will be an airlock.

I suspect Wammers or Grrrr who have more dealings with the weasely diesely P38 will be more help.
 
kevind said:
Hi, sorry to hijack the thread but I have similar probs, mine is the 2.5 weasel. with new rad all cooling pipes and recently replaced head gasket, head was skimmed ( cant remember by how much ) and pressure tested at same time. Tried bleeding as rave also by removing top overflow pipe ( rad to header tank) connecting clear pipe from rad and allowing to flow back into header tank. It will idle for ages and stay roughly at 12oclock on gauge move it 100yds and its straight into the red on gauge. A ll ideas welcome, many thanks.
Click to expand...

Don't think your ment to skim the heads on the diesel, an oil burner will be along shortly to confirm, also did you do the baffle test on your new rad ???
 
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