Newbie needing help with p38 overheating !

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Just wanted to say "thanks" to those that replied (whether by above or private message) - you gave me the confidence to go for it on replacing the radiator - and saved me panicking when i experienced the dreaded nut and bolt corrosion/fusing at the bottom bracket!

New rad plus flush and refill have pretty much cured the issue. One minor symptom remains, on which I'd much welcome further guidance.

The handbook symbol comes on the air con when engine up to temperature (or shortly thereafter). The temp gauge then creeps slowly up to virtually the top of the normal range on the gauge (no light indicating overheating). If I turn a/c off and heater temp right up (to HI or near HI) it brings engine temperature down to mid gauge within 30-60 secs. So it's a relatively minor gripe that I can live with to avoid engine seizure. That said, it'd be nice to get a proper fix rather than rely on the cabin heater to be augmenting the radiator's job!

In doing the work on rad replacement I noticed a couple of things that are almost certainly relevant (?)

1. A/c condenser is pretty clearly shot - must be the original - fins falling out all over the place !
2. The auxiliary fans (in front of the a/c condenser) don't kick in at any point. I'm guessing they should when the engine temp gets high and there is an increased demand/load from a/c to cool.

I'm deducing that I need a new condenser complete with fans. Plus a regas.

Just want to check that my logic above sounds right - and that this is a fix I can do myself (comparable to radiator replacement)? Looks it from research I have done, but I don't want to get overconfident or underestimate the niggly bits ! And/or if there is a well known issue e.g. electricals that might be stopping the fans kick in (NB I've checked fuses, all fine) then someone may be able to give me a cheap and easy save here?!

Thanks in advance.
 
Last edited:
Gus Driver said:
Just wanted to say "thanks" to those that replied (whether by above or private message) - you gave me the confidence to go for it on replacing the radiator - and saved me panicking when i experienced the dreaded nut and bolt corrosion/fusing at the bottom bracket!

New rad plus flush and refill have pretty much cured the issue. One minor symptom remains, on which I'd much welcome further guidance.

The handbook symbol comes on the air con when engine up to temperature (or shortly thereafter). The temp gauge then creeps slowly up to virtually the top of the normal range on
the gauge (no light indicating overheating). If I turn a/c off and heater temp right up (to HI or near HI) it brings engine temperature down to mid gauge within 30-60 secs. So it's a relatively minor gripe that I can live with to avoid engine seizure. That said, it'd be nice to get a proper fix rather than rely on the cabin heater to be augmenting the radiator's job!

In doing the work on rad replacement I noticed a couple of things that are almost certainly relevant (?)

1. A/c condenser is pretty clearly shot - must be the original - fins falling out all over the place !
2. The auxiliary fans (in front of the a/c condenser) don't kick in at any point. I'm guessing they should when the engine temp gets high and there is an increased demand/load from a/c to cool.

I'm deducing that I need a new condenser complete with fans. Plus a regas.

Just want to check that my logic above sounds right - and that this is a fix I can do myself (comparable to radiator replacement)? Looks it from research I have done, but I don't want to get overconfident or underestimate the niggly bits ! And/or if there is a well known issue e.g. electricals that might be stopping the fans kick in (NB I've checked fuses, all fine) then someone may be able to give me a cheap and easy save here?!

Thanks in advance.
Click to expand...
Most likely the viscous fan is faulty, do the newspaper test.
The electric fans only run when the aircon demands they run, NOT on engine temperature. If there is no gas in the system, the fans will not run. Post 99 there is another sensor that is supposed to trigger the electric fans in an overheat situation, but it is set so high that the red light will be on by the time it triggers the fans.
Most likely the condensor is faulty and leaking gas, common problem. Have a leak test done.
 
Datatek said:
Most likely the viscous fan is faulty, do the newspaper test.
The electric fans only run when the aircon demands they run, NOT on engine temperature. If there is no gas in the system, the fans will not run. Post 99 there is another sensor that is supposed to trigger the electric fans in an overheat situation, but it is set so high that the red light will be on by the time it triggers the fans.
Most likely the condensor is faulty and leaking gas, common problem. Have a leak test done.
Click to expand...
Thank you, extremely helpful. Not the viscous fan - that's working fine (apols, should have said). It's a '98 GEMS and the a/c is clearly not working, prob due to combination of no gas and condenser being shot. That said, when I put a/c on and set to low temp the fans don't come on (and the necessary demand would be being created, wouldn't it)?
 
Gus Driver said:
Thank you, extremely helpful. Not the viscous fan - that's working fine (apols, should have said). It's a '98 GEMS and the a/c is clearly not working, prob due to combination of no gas and condenser being shot. That said, when I put a/c on and set to low temp the fans don't come on (and the necessary demand would be being created, wouldn't it)?
Click to expand...
Sorry, the sensor is for diesel, should read more carefully. The fans ONLY come on when the gas pressure rises enough to operate the tristate switch, your dash setting means nothing. I believe the engine ECU can call the fans on an overheat on the V8, but I do not know the V8.
If the viscous fan is OK and the car overheats as described, then you have another problem. Could be the condensor is so corroded that it is blocking the airflow, a duff thermostat or even a water pump..
 
Hi. Original poster picking up on this again. I had the a/c vacuum tested and regassed (fair play to In 'n' Out who did it for £49 inc 1300g of refrigerant). Drove 500mile round trip in really hot weather and needed to manage engine overheating through regularly turning cabin heater to full.

The condenser fans aren't kicking in. My reckoning is that if they did, then I wouldn't get overheating (or, at least, I'd get less).

Sometimes on the HVAC cabin controls the handbook sign shows, then disappears, then shows again. I'm thinking that's consistent with pressure switches "calling off"/demanding the condenser fans start-up; with fault then showing because the fans don't start up as the pressure switches demand (and fault going off again once pressure switch removes the demand)?

I've checked fuses 34, 42 and 43 - fine.

Bridging relays 18, 13 and 14 causes condenser fan startup. Each individually works. So I suspect it's a relay issue - but how do I know which one is at fault?

Any guidance/help welcomed !

Still in love with the car despite myself.....
 
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Datatek mod is for dieselbtw I'm still convinced you have another issue. The cooling on these dispite what folk say is plenty enough. Swap the heart valve thermostat for a new one( must be original maker though) don't be tempted to buy the cheap one!
 
Gus Driver said:
Hi. Original poster picking up on this again. I had the a/c vacuum tested and regassed (fair play to In 'n' Out who did it for £49 inc 1300g of refrigerant). Drove 500mile round trip in really hot weather and needed to manage engine overheating through regularly turning cabin heater to full.

The condenser fans aren't kicking in. My reckoning is that if they did, then I wouldn't get overheating (or, at least, I'd get less).

Sometimes on the HVAC cabin controls the handbook sign shows, then disappears, then shows again. I'm thinking that's consistent with pressure switches "calling off"/demanding the condenser fans start-up; with fault then showing because the fans don't start up as the pressure switches demand (and fault going off again once pressure switch removes the demand)?

I've checked fuses 34, 42 and 43 - fine.

Bridging relays 18, 13 and 14 causes condenser fan startup. Each individually works. So I suspect it's a relay issue - but how do I know which one is at fault?

Any guidance/help welcomed !

Still in love with the car despite myself.....
Click to expand...
On my car, the wire from the tri state switch to the fuse box was open circuit, so the fans never ran on aircon demand. The book symbol is not likely to be due to the aircon, there is no feed back from the aircon to the HEVAC certainly on later models where there is a relay in the compressor circuit.
You can swap the relays for any other relay of the same colour to test them.
 
My AC fans are totally seized so disconnected. Prior to the gas leaking out of the aircon, it travelled thousands of miles with the aircon on cold in Europe with the outside temp well into the mid 30's. Didn't matter if I was doing 90 or stopped, the gauge never moves.

Frankly, if you're having to put the cabin heater on full to keep the temp down, something else is amiss.

The viscous fan will have little to no effect above about 30mph so if it's overheating on the motorway, you need to be looking elsewhere.

Sounds to me like you are not getting sufficient coolant flow through the main radiator but plenty through the heater matrix.

I would be checking the pipework and making sure it's all clear and not kinked or delaminated inside.
 
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