P38A Another P38 Overheating Problem

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What thermostat did you get? there are at lest 2 types, summer and winter, both open at different temps
 
I think the fact that it's better now you fixed the fan is a huge clue.
I'd be looking very closely at said fan if it were me!
 
Dopey said:
How is that possible, the thread runs opposite to the way it runs??
Click to expand...

Well, I thought that but it's a left handed thread so goes you loosen by rotating the nut clockwise (as you look at it from the front). The fan spins that way as well which I can't get my head around as it seems like a me it would unscrew (although I'm sure that isn't right). Either way it fell of

The fan seems to be on all the time (using the rolled up newspaper test). Is there anytime when the fan isn't supposed to be running? If it is running from cold, what is the point in having it on a clutch??

Dopey said:
What thermostat did you get? there are at lest 2 types, summer and winter, both open at different temps
Click to expand...

I got this one. Doesn't mention summer or winter spec

http://www.island-4x4.co.uk/thermostat-britpart-stc3338-p-391.html



Wazzajnr said:
I think the fact that it's better now you fixed the fan is a huge clue.
I'd be looking very closely at said fan if it were me!
Click to expand...

It's a new fan and clutch. I did stick a hose down the top hose to try and flush it out so maybe that helped. Can't find any other way of flushing any of the other lines though.

Still don't know what would be affected or made more efficient by the engine speed!?!

Will d finitely be doing a write up when this one is solved. Driving me nuts!!
 
Grrrrrr said:
Petrol has normal thread on the viscous fan; diesel has reverse thread. Just nip it up. Turning without the holding tool can break it.
Click to expand...

Yeah, I've put it on an tightened it a bit more. Seems to be ok now.

Still can't work out why engine speed affects the cooling in the way it seems to (I.e higher engine speed, better cooling).
 
Renniks said:
Well, I thought that but it's a left handed thread so goes you loosen by rotating the nut clockwise (as you look at it from the front). The fan spins that way as well which I can't get my head around as it seems like a me it would unscrew (although I'm sure that isn't right). Either way it fell of

The fan seems to be on all the time (using the rolled up newspaper test). Is there anytime when the fan isn't supposed to be running? If it is running from cold, what is the point in having it on a clutch??



I got this one. Doesn't mention summer or winter spec

http://www.island-4x4.co.uk/thermostat-britpart-stc3338-p-391.html





It's a new fan and clutch. I did stick a hose down the top hose to try and flush it out so maybe that helped. Can't find any other way of flushing any of the other lines though.

Still don't know what would be affected or made more efficient by the engine speed!?!

Will d finitely be doing a write up when this one is solved. Driving me nuts!!
Click to expand...
Is the new fan the correct diameter and blade pitch? Is the cowl fitted correctly.
It seems to me like there is a lack of airflow through the fins or there is some blockage in the radiator making it less efficient.
Have you still got the old fan?
 
Wazzajnr said:
Is the new fan the correct diameter and blade pitch? Is the cowl fitted correctly.
It seems to me like there is a lack of airflow through the fins or there is some blockage in the radiator making it less efficient.
Have you still got the old fan?
Click to expand...

Fan came as one unit from island 4x4, it fits the cowl etc perfectly.

Anyway, I think I may have got to the bottom of the issue, sort of.... I switched the aircon off. I knew there was an issue with the HVAC and suspected aircon as if I turn the aircon to off, the book symbol goes out.

So I switched the aircon off and went on a run on the motorway then came to a stop. This would usually send the needle into the red until,I revved the engine. However, this time, the need, went a bit above halfway but not near the red, then came back down without me doing anything.

Likewise on the motorway, if I sit at 60-65, the needle stays dead centre. Push it to 70-75 and the needle starts to creep up but then seems to come back down and comes back down very quickly, if I back off a little.

I don't think it is completely fixed but I think the aircon pump must have been putting too great a strain so as the waterpump wasn't running at its maximum when at idle. Hence, if the engine was quite cool it was ok as it just needed to maintain temp, but if the pump needed to be at max in order to bring the temp down, it wasn't.

Does the above make mechanical sense to anybody or have I just made it up!?!

Additionally, the two Aux fans on the very front of the radiator stack (think they are attached to the intercooler), never seem to come on. Does anybody know when they should come on and what triggers them?
 
Renniks said:
Fan came as one unit from island 4x4, it fits the cowl etc perfectly.

Anyway, I think I may have got to the bottom of the issue, sort of.... I switched the aircon off. I knew there was an issue with the HVAC and suspected aircon as if I turn the aircon to off, the book symbol goes out.

So I switched the aircon off and went on a run on the motorway then came to a stop. This would usually send the needle into the red until,I revved the engine. However, this time, the need, went a bit above halfway but not near the red, then came back down without me doing anything.

Likewise on the motorway, if I sit at 60-65, the needle stays dead centre. Push it to 70-75 and the needle starts to creep up but then seems to come back down and comes back down very quickly, if I back off a little.

I don't think it is completely fixed but I think the aircon pump must have been putting too great a strain so as the waterpump wasn't running at its maximum when at idle. Hence, if the engine was quite cool it was ok as it just needed to maintain temp, but if the pump needed to be at max in order to bring the temp down, it wasn't.

Does the above make mechanical sense to anybody or have I just made it up!?!

Additionally, the two Aux fans on the very front of the radiator stack (think they are attached to the intercooler), never seem to come on. Does anybody know when they should come on and what triggers them?
Click to expand...
Personally, I think you're barking up the wrong tree there.
The load from the aircon pump is miniscule compared to pushing a 2.5 ton brick through the air at motorway speeds.
Just remind me, is it a petrol or a diesel?
For what it's worth, my two aircon fans are seized solid but in a traffic jam in height of summer in Germany (over 30deg outside) the gauge never moved and the aircon was running hard to keep me cool. This lasted for about 45 minutes.
I also often do 80+ mph on the autobahns and then drop straight into the services with not discernable movement on the gauge.
I still think that you have some issues with your cooling system and turning the aircon off just means you're putting slightly less heat into the system.
You need to find the root cause before you cook the motor and find yourself in a world of pain.
 
Wazzajnr said:
Personally, I think you're barking up the wrong tree there.
The load from the aircon pump is miniscule compared to pushing a 2.5 ton brick through the air at motorway speeds.
Just remind me, is it a petrol or a diesel?
For what it's worth, my two aircon fans are seized solid but in a traffic jam in height of summer in Germany (over 30deg outside) the gauge never moved and the aircon was running hard to keep me cool. This lasted for about 45 minutes.
I also often do 80+ mph on the autobahns and then drop straight into the services with not discernable movement on the gauge.
I still think that you have some issues with your cooling system and turning the aircon off just means you're putting slightly less heat into the system.
You need to find the root cause before you cook the motor and find yourself in a world of pain.
Click to expand...

Yeah, I don't think I've bottomed the problem out yet, but it is certainly getting better. I think it must be a blockage somewhere in the system; problem is I struggle to get a hose in anywhere to flush the system through.

I'm thinking of dropping the coolant again and putting some of that coolant flush stuff in with some water before draining again and refilling with coolant.

Ps: it's a diesel
 
OK, I seem to recall @wammers saying that on later diesels there is an extra temp sender on the head that's designed to bring in the aircon fans if the viscous fan isn't coping. Maybe that is the bit that isn't working?
 
In fact, check the sensors don't have anti freeze fuzz around them, under the manifold. One of mine caused a problems with the torque lock up on the motorway!! It was leaking ever so slightly and the little head on it was fuzzy and loose. o_O
 
I cant remember but have you checked the small pipe top left of rad is clear and with the engine running expansion cap of you should get a constant trickle of coolant out of it in the tank.
 
brianp38dse said:
I cant remember but have you checked the small pipe top left of rad is clear and with the engine running expansion cap of you should get a constant trickle of coolant out of it in the tank.
Click to expand...

I've checked it and it is clear. I don't get a constant stream of water though. In fact, I can't seem to remember getting any with the engine running...
 
I may be wrong with engine running, but I do get more out when squeezing the left hose, just try to fathom out what you have going on.
 
I get a constant stream of coolant from the small return pipe into the expansion tank when it's running!
You should also?
I think we talked about this on another thread:confused:o_O
 
Wazzajnr said:
Personally, I think you're barking up the wrong tree there.
The load from the aircon pump is miniscule compared to pushing a 2.5 ton brick through the air at motorway speeds.
Click to expand...

IF it is working properly. What if the aircon pump is seizing?

We're not there and if he's sure it gets worse with the air con off (i.e. the A/C light is on) then it is something to consider.
 
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