over heating at speed

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G

gazzatops

Member
Posts
15
Hi
I have a problem , surprise , my P38 has started to over heat . I was told it could be the thermostat so have replaced that and also the two sensors on top of the engine , but no joy :mad:
I flushed and bled the water system but still she keeps overheating ,
The unusual thing is if I drive around keeping the revs to about 2000 no problems , again I can leave her ticking over and again no problem
The temp only goes up when on the motorway , any one had the same problem or know what the cause may be ?:confused:
Also I have noticed that the two electric fans don’t come on at all , I have tested them and they do work not sure if that may have something to do with it
 
Helps to tell us if it's petrol or diesel. On the diesel the electric fans only operate to cool the aircon condensor, on the V8 the engine ECU can also cause them to operate in an engine overheat situation. I can give you a mod to use the electric fans for cooling.
 
water pump might as well try a new on as there only £25,
rad check if its hot all over,
duff new stat, did you test if b4 you put it in,
hg failer if the above has been done go get a sniff test,
slipped liner if its this you dont want to know
 
sorry its a petrol 4.6 , the rad gets hot all over and i have no water loss
Datatek if you can let me know that mod please i will give it a try .
not sure how you test the thermostat , so i just put in the new one.
if the rad was blocked would i not get cold spots on it ?
will have a look at the waterpump but looking in the filler cap the water seams to flow .
 
Have you checked air flow through the radiator. Check your condenser core and rad core are not full of debris.
 
gazzatops said:
sorry its a petrol 4.6 , the rad gets hot all over and i have no water loss
Datatek if you can let me know that mod please i will give it a try .
not sure how you test the thermostat , so i just put in the new one.
if the rad was blocked would i not get cold spots on it ?
will have a look at the waterpump but looking in the filler cap the water seams to flow .
Click to expand...

Faulty pressure cap or not fully tightened down will also cause overheating.
Test a stat by putting it in boiling water, many new ones are faulty.
Even if the RAD gets hot all over it does not mean that the flow is not being reduced by the build up of crap in the water galleries.
If you want the aircon fans mod PM me with an email address, however it is not intended that this mod should be used to mask an existing cooling problem except as a back up to the viscous on the V8.
 
odd's on it's the water pump. On the originals the impeller (plastic) is sort of bonded to the rotation shaft and, over time, the bond breaks mening that teh impeller isn;t turning as fast as it should, water doesn't flow as it should and she starts to overheat.

there are 2 waterpumps, one is less than £30 but has the plastic impeller and the other, about £55 had a bronze impeller which is part of the rotatin shaft.

I changed mine earlier this year and the water flow is loads better
 
hi, in my past experience with the v8s only getting hot when driven hard or fast on motorway, is down to not enough cooling , fit a new radiator less than a £100 nowadays and im pretty sure it will cure your problem

regards jim
 
Hawaii said:
odd's on it's the water pump. On the originals the impeller (plastic) is sort of bonded to the rotation shaft and, over time, the bond breaks mening that teh impeller isn;t turning as fast as it should, water doesn't flow as it should and she starts to overheat.

there are 2 waterpumps, one is less than £30 but has the plastic impeller and the other, about £55 had a bronze impeller which is part of the rotatin shaft.

I changed mine earlier this year and the water flow is loads better
Click to expand...

i paid £25ish for one with a steal impeller from ces
 
im back and still have the same problem , i have replaced the waterpump , flushed the system and replaced the rad , i have also fitted another stat but still over heats at speed , still no water loss anyone have idea of what it could be :confused:
 
Hawaii said:
odd's on it's the water pump. On the originals the impeller (plastic) is sort of bonded to the rotation shaft and, over time, the bond breaks mening that teh impeller isn;t turning as fast as it should, water doesn't flow as it should and she starts to overheat.

there are 2 waterpumps, one is less than £30 but has the plastic impeller and the other, about £55 had a bronze impeller which is part of the rotatin shaft.

I changed mine earlier this year and the water flow is loads better
Click to expand...

This is common on all makes of cars, I'd start by checking the pump iusn't going to cost you anything to look.
 
Check rad is a good one...i.e. should get hot all over not just on the top.
50% water/antifreeze mix?
Viscous fan test as mentioned...
Drain and refill the system as per rave to avoid air locks, recent thread on this: http://www.landyzone.co.uk/lz/f10/water-air-lock-199867.html

V8 though...so i think your problem may lie in the block itself...slipped/cracked liners.
Possibility of running lean?
 
Last edited:
how can it be the fan if the car overheats at speed? Fans do nothing once the car is moving at more than 20ish mph.....

Pump and rad both new

The only thing I can think of is that the new thermostat is not working properly (did you test it as there are lots of reports on here of faulty new thermostats) or there is a blockage somewhere that is restricting flow.

Odd one this.........


Cheers

Jerry
 
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