P38A Another P38 Overheating Problem

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Aircon fans only come on to assist cooling on 1999 MY and on. Make sure condenser and rad are clear of debris. Check viscous fan as said earlier.
 
Well I've decided to just drain the whole system and refill, hopefully eliminating air locks. I'm in 2 minds about the thermostat; some say it's easy to change without having to remove anything else, others say the fan and other things need to come out. I'll have a good look before deciding whether to change it I think.

Thanks everybody for their help so far. I'll keep you posted with how I go
 
;):)you will be able to get to the thermostat housing when you have removed the fan. The bolts take a bit of finding. Refit the new thermostat with the little hole at 12.00 o'clock, the help to purge the engine of air! You'll understand when you have the thermostat in hand..give the water pump a spin by hand while you at it, any noises then it's usually worn. That one visit could reveal possible problems. Good luck :);)
 
As long as the rad is ok just change the stat and pump for what it costs. While the pump and stat are out get a hose pipe down there and flush it all out. If theres still a prob then you ave a real prob. Head might be next.
 
Renniks said:
Well I've decided to just drain the whole system and refill, hopefully eliminating air locks. I'm in 2 minds about the thermostat; some say it's easy to change without having to remove anything else, others say the fan and other things need to come out. I'll have a good look before deciding whether to change it I think.

Thanks everybody for their help so far. I'll keep you posted with how I go
Click to expand...

No need to drain for an airlock. The pipe from top of rad to expansion tank must be free. All your symptoms point at fan.

if you do decide to go in then listen to Tony and fit the decent water pump with metal impeller. It only costs a few quid more at about £30.
 
Grrrrrr said:
No need to drain for an airlock. The pipe from top of rad to expansion tank must be free. All your symptoms point at fan.

if you do decide to go in then listen to Tony and fit the decent water pump with metal impeller. It only costs a few quid more at about £30.
Click to expand...

Sorry Grrrrr, what do you mean by not needing to drain the system to get rid of the airlock? Are you saying that I just need to take off a hose and, then, I'm guessing, run the engine?

The fan seems to be working fine, even from cold. When it is overheating, the fan is still engaged. In honesty, I wish it was the fan as that would be a known fix.

Yeah, if I go in, I will definitely fit a pump with a metal impeller. If I don't need to drain the system to get rid of an airlock, I will try that first. If that doesn't cure it and I need to drain the system, I will probably just change the thermostat and the water pump to try and take away any potential issues.

Cheap P38's I'm understanding why people always say steer clear!!
 
Renniks said:
Sorry Grrrrr, what do you mean by not needing to drain the system to get rid of the airlock? Are you saying that I just need to take off a hose and, then, I'm guessing, run the engine?

The fan seems to be working fine, even from cold. When it is overheating, the fan is still engaged. In honesty, I wish it was the fan as that would be a known fix.

Yeah, if I go in, I will definitely fit a pump with a metal impeller. If I don't need to drain the system to get rid of an airlock, I will try that first. If that doesn't cure it and I need to drain the system, I will probably just change the thermostat and the water pump to try and take away any potential issues.

Cheap P38's I'm understanding why people always say steer clear!!
Click to expand...

Yes. Take off the thin pipe to expansion tank and blow into it to make sure it is clear. Take the cap off the expansion cap and run the engine, squeezing the hoses by hand to try and push any bubbles through. Sometimes a bit of throttle (2000 rpm) helps chase air through. If you take the fan off feel the rad for cold spots. If it feels like the top of the rad is hot and the bottom cold then rad might not have the baffle to force the water down one side and up the other so the water just skims along the top.

Be glad you got a cheap one. Even the expensive ones have issues so you'd just be further out of pocket.
 
Grrrrrr said:
Yes. Take off the thin pipe to expansion tank and blow into it to make sure it is clear. Take the cap off the expansion cap and run the engine, squeezing the hoses by hand to try and push any bubbles through. Sometimes a bit of throttle (2000 rpm) helps chase air through. If you take the fan off feel the rad for cold spots. If it feels like the top of the rad is hot and the bottom cold then rad might not have the baffle to force the water down one side and up the other so the water just skims along the top.

Be glad you got a cheap one. Even the expensive ones have issues so you'd just be further out of pocket.
Click to expand...

Right, I get you. Essentially vent it through the expansion bottle but make sure the expansion bottle hose is clear first. I'll give it a go! Thanks for the tips.

I'll try this first. If it doesn't fix it, I'll go with the draining and changing of the thermostat and water pump.

I didn't buy a P38 to get back into mechanics (I used to be an aircraft engineer in a previous life) and have had new cars for the last 10 years or so. However, I'm actually quite enjoying messing around and doing little jobs on it. The wealth of information on this forum is amazing and invaluable; hopefully I will be able to have some knowledge to pass on in the future!

That's a good way of thinking about buying a cheap one, although I think you are just being kind :)
 
Ok, so just thought I'd give you an update. It seems that the overheating issue has now 'fixed itself'. I ran the car up to temperature on the drive and, initially, just went to feel the pipes coming off the rad to see if they were hot etc. The right hand pipe was hot, the left hand pipe was cool. I gave it a few squeezes to see if it was pressurised or not.

I then got back in the car and waited to see if it got hot; it stayed bang in the middle. I revved the engine and kept it at 2k for a while, still bang in the middle.

This wasn't particularly unexpected as it had seemed to do this before. However something just seemed a little different as the needle would creep slightly over halfway, and then come back down (as you would expect). As such, I thought I would take it for a run and see if it did the same as before, I.e go into the red when stationary after a run.

So I pulled over and sat there and.... nothing. The needle behaved perfectly and didn't get hot at all. It seems I have a phantom mechanic hiding in the garage - a very handy thing to have widen you buy a cheap P38!

I'm pretty sure it must be an airlock somewhere that has either 'fixed itself' or my squezzing of the pipes has moved it along. Either way I am a bit perplexed as to what to do. I don't really want to disturb anything now as it is running like a dream but I'm a bit nervous that the problem isn't actually fixed. I think I'm going to go with the phrase 'if it ain't broke...'

I'm pretty sure I haven't fixed it though as I didn't even take the cap off the expansion bottle! Watch for the update in 48hours after it has miraculously returned!!

In the meantime, thank you all for your suggestions!!
 
Water pump.
I had a vauxhall cavalier once that did exactly the same. The impeller was loose on the shaft. When driving there was enough for it to work but at idle it would work sometimes but not others.
I changed the head gasket twice thinking that was the problem but then found that every time it got hot, a good blip on the throttle would bring the temp straight down.
If it's not a massive job, I'd be changing the water pump.
 
Wazzajnr said:
Water pump.
I had a vauxhall cavalier once that did exactly the same. The impeller was loose on the shaft. When driving there was enough for it to work but at idle it would work sometimes but not others.
I changed the head gasket twice thinking that was the problem but then found that every time it got hot, a good blip on the throttle would bring the temp straight down.
If it's not a massive job, I'd be changing the water pump.
Click to expand...

Could be a good bit of preventative maintenance there. You want the metal impeller anyway in case the plastic one disintegrates. Only costs about £30 from Island. Do the stat at the same time and you should have no worries and peace of mine for the sake of £50.
 
Grrrrrr said:
Could be a good bit of preventative maintenance there. You want the metal impeller anyway in case the plastic one disintegrates. Only costs about £30 from Island. Do the stat at the same time and you should have no worries and peace of mine for the sake of £50.
Click to expand...

Water pump metal impeller is about £45.00. Valeo thermostat about £15.00. Still think fan is favourite. ;)
 
wammers said:
Maybe, the money markets will be making billions on the strength of Brexit, setting artificial rates. But pound is not 33% less valued surely.
Click to expand...
In my experience of transferring funds to Czech Republic it is about 20% down on where it was pre referendum.
Seems to be about the same on most other currencies I've dealt with recently too.
It's actually great for me as the vast majority of my sales are overseas so busy as hell at the moment because my prices have effectively gone down by 20%.
That's a big difference on a 20k order. It will drop off though as our parts go up in price and we have to increase prices.
 
Thanks for the advice guys. I'll do a few short trips over the next few days and see how it goes. I think I will end up changing the water pump and thermostat anyway, as I will be forever nervous!!
 
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