p38 overheating...

oops, just posted this in the newbie say hello section , doh !!! :doh:
Hello all, i hope you good folk can help me upon my way. I run a 98' p38 4.6 hse running on lpg. I have owned the car since april this year and on two occasions the car has overheated. Once on its first run down the m6, after an hour of travelling at a steady 70mph, we pulled into traffic, and after 5 mins the temp gauge rose up to the red, i pulled off and the car cooled. All was well, until today, after a steady drive through town traffic the car came to a halt where it stood on tick over for about 5mins when the temp gauge again rose to red, it cooled and drove ok. In the time i have run the car ,the temp gauge reaches halfway and stays there, plenty of coolant in the system, top hose isn;'t too hard, water passes through small hose to header and other than two occasions has run faultless. Now i know im not expecting a specific how to fix, but could anybody ,who hasn't fallen asleep by now, point me in the right direction.

:welcome2: lol, dont worry mate, im sure you wont be the last, Are you losing coolant though?

No, the coolant level remains correct throughout. The problem is only in standing traffic as mentioned, on the move, i can be travelling any distance, any speed as long as i am moving, The two occasions it has got hot have both been on a very hot day. perhaps i need to make sure the coolant mixture is correct ?

There is a very fine line between a good and bad cooling system on a P38. As a result it needs rather more attention paid to it that would normally be expected. Just checking the coolant level is OK just won't cut it as you now know.
Chances are your radiator is restricted or the air con condensor which sits in front of the radiator is blocked. If you don't know the history of when your radiator was last replaced it might be worth doing. £70 and an hours labour is well worth it.

weekendangler said:

No, the coolant level remains correct throughout. The problem is only in standing traffic as mentioned, on the move, i can be travelling any distance, any speed as long as i am moving, The two occasions it has got hot have both been on a very hot day. perhaps i need to make sure the coolant mixture is correct ?

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Check the viscous cooling fan:doh:

its a bit of a late reply, but thankyou all for your advice. I ended up having the water pump, viscous coupling and thermostat replaced, (all new parts) and all was good. After a 3 day round trip to cornwall this weekend covering about 800miles, the car decided to start overheating after 2 hrs on the return home. Stopping the car straight away, i waited ten mins then slowly opened the rad cap a bit at a time to release the pressure.In doing so i heard the radiator bubble and gurgle like a hungry tummy. After i while i could take the cap right off and the coolant,although hot was just above the cold mark. I set off again taking it easy,and made the 5 hour journey back to blackpool no problem. This morning, i topped up with about 300ml of coolant and now the lpg clicks over really quick, at a lower temp gauge. I also noticed the top hose used to be under a lot of pressure and i thought perhaps head gasket, however today the top hose is still quite squishy even when at full temp? whatever the problem, it seems to have gone away...

I had very similar problems with my 2000 V8 also on LPG. Overheated on 2 occasions - both after a good run when I'd been stopped for a few minutes . Changed the expansion cap and the radiator, had the block pressure tested and "sniff" tested - all ok. At this time, I was topping the coolant up regularly. It eventually developed a noticeable missfire and after stripping the engine down at my local indy, we found cylinder 7 had slipped a liner.

I chose to go for a replacement engine from Turners - not a cheap fix - and all's now well! I chose to go for top-hat liners and new oil and water pumps. Combined with new coils, plugs and leads, it now runs superbl y

id still check the viscus fan and see if its engaging, then also considder putting in an aux fan to help cool when needed.

i will see how it runs these next couple of weeks and obviously keep a check on the coolant level. The viscous fan coupling was changed and the fan makes more of a noise now, so i guess its whirling around as it should, all the same though im not out of the woods yet... if all else fails then yes , a secondary fan will be rigged up.

I had a simler problem recently except mine overheated when towing
Check radiator is getting hot all over check all pipes are getting hot also my rad cap wasnt holding enough pressure im suprised but it did make a differance
As for the fan if the radiators not heating properly the fluid in it wont get hot and the fan wont kick in

weekendangler said:

i will see how it runs these next couple of weeks and obviously keep a check on the coolant level. The viscous fan coupling was changed and the fan makes more of a noise now, so i guess its whirling around as it should, all the same though im not out of the woods yet... if all else fails then yes , a secondary fan will be rigged up.

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Have a word with datatec on heer he has a mod that sets the ac fans to work as aux cooling

You may have had an air lock. Bleed the system. Then as others have said, check the airflow.

just reread the thread
check the rad core for "cold spots" they do get cloged up and show up as random overheating more so on hot days, long runs at low speeds ect...

bit late in the day, but i may have found the problem. A few weeks back after a bit of a do with a merc, i pulled into tesco only to see water pouring down from the rear of the engine over the gearbox. Assuming a core plug had popped it was taken to a garage on the back of an AA truck. Turned out to be headgasket. Imagine my wifes excitement when i handed over a fist full of dollars 4 days before xmas...smashing, back on the road again, well i am now i replaced the crappy plugs they fitted with my usual brisk ones, (ooh that lpg does like a good spark)