Temperature creep under load

[WOLFN8TR]

Quick update: I did a compression check on the engine today. All cylinder psi consistent across the board.

The AC is cold in the cabin but I can hear the compressor cycle on/off a lot. I’m wondering if its the compressor causing drag on the motor after all?

I still need to install my new radiator, I’ll do that sometime tomorrow along with cleaning out the AC condenser.

Good to hear it's not a head gasket! Sounds like you need to check the AC for proper freon levels.

Inefficient Cooling
The most obvious sign of an overcharged AC system is poor cooling. Without room to depressurize the coolant, the AC system simply stops functioning. You might still get a cool breeze coming from the vents, but just as often you could get room-temperature or even hot air. Some systems will shut themselves off if they detect improper pressure release in the system. Be glad if yours does; it may be saving you from a hefty repair bill.

Compressor Noise
The compressor might make excessive noise, the sound of it struggling to shove liquid coolant through a tiny nozzle designed for gas molecules. This doesn't happen in every case, since some AC compressors are designed with a bypass to prevent excess internal pressure from straining the pump. If you've ever heard a power steering pump going bad, then you'll have some idea of what a struggling AC compressor sounds like.

High Pressure Readings
An overcharged AC will show higher than normal pressure and temperature readings. The compressor works harder to try balancing out the system, which results in more pressure. The higher the pressure, the higher the temperature rise as a result. This causes even more pressure to build, resulting in a cascade failure of cooling capacity.

Struggling Engine
An AC compressor can draw a significant amount of power from the engine, never more so than when it's trying to push a gallon of coolant through a one-ounce nozzle. This excessive power draw can cause the compressor's drive belt to slip and screech, which generally precedes a loud snap and belt failure. Or, the belt may hang on, and sap power from the engine. In this case, you may end up with a low or fluctuating idle, sluggish acceleration and excessive loss of fuel economy when the AC is running.

Broken Compressor
This is often the inevitable end result of a chronically overcharged system. The compressor is your AC system's heart, and eventually it's going to respond the same way your heart would if you had chronic high blood pressure. Internal seals will fail, valves will cease to function, the pump will fail and the system will ultimately flatline.

[bigjae46]

I'd replace the condensor. The condensor is in front of the radiator so it takes the brunt of all the road debris. Your radiator should be in decent shape, might just need to be blown out with some compressed air. Make sure you REMOVE the radiator from the car otherwise you just blow it back into the condensor.

Here's a pic of a 2001 track driven M3's condensor. He was having water temp issues. The silver color represents bent fins. I'm sure the rest of it is covered in crud which further reduces the condensor's effectiveness.

[0-60motorsports]

Still over heating but note taking longer to do it. So the changing the dries helped but a little. Net steep change out expansion valve and check compressor.

[slavik1988]

Quick update: I did a compression check on the engine today. All cylinder psi consistent across the board.

1. 152
2. 151
3. 154
4. 151
5. 150
6. 154

The AC is cold in the cabin but I can hear the compressor cycle on/off a lot. I’m wondering if its the compressor causing drag on the motor after all?

I still need to install my new radiator, I’ll do that sometime tomorrow along with cleaning out the AC condenser.

The radiator will not do you any good. I am having the same issue with it overheating under load and without the a/c on.. I replaced the radiator with a Genuine BMW unit and a Genuine water pump as well. Still having the same issue. Will be buying a new a/c condenser to test that theory as well. Car has only 57k miles.

I also did a compression and leak down test on my car. All was in good order.

[8000RPM]

Interesting. Since your situation is unaffected by the A/C being on/off, I would lean toward not having enough air cooling the radiator. With compression testing okay, and you’ve replaced the other obvious things, I agree it makes sense that it could be the condenser blocking airflow.

Mine is different. As soon as I turn the A/C off going up a hill, the temp will come back down. I’m also bewildered that when the temp comes down, it swings down to a bit left of center. The car will be down for the next week or so while I replace rod bearings and front suspension bits. I’m going to clean our the condenser fins while the radiator is out. Hopefully that fixes it but Its also a possibility it could be the compressor as it cycles on/off more than it should.

The radiator will not do you any good. I am having the same issue with it overheating under load and without the a/c on.. I replaced the radiator with a Genuine BMW unit and a Genuine water pump as well. Still having the same issue. Will be buying a new a/c condenser to test that theory as well. Car has only 57k miles.

I also did a compression and leak down test on my car. All was in good order.

[0-60motorsports]

So while I was speaking to the tech today he was telling me when the car Overheats with the AC on he noticed two things. 1: the condenser heats up 2: the ac pressures increase, high side is almost at 300psi which is 50 over normal and low side is 30psi over normal.

This leads me to believe that it could be the compressor and even though the condenser is one year old I’ll change it out as it’s cheap enough. Waiting for final word and correct compressor pn from the shop so that I can order it if it is needed today.

[8000RPM]

How are you getting the a/c pressures? Hooking up gauges under the hood? Are the pressures high even from the start?

FCP shows this is the compressor for a prod date from 09/02. I’m pretty sure Denso is the OE for BMW for a/c compressors. https://www.fcpeuro.com/products/bmw...em-64526936883

Does anyone know who is OE for the condenser and drier? I think the drier is Rein (based on sticker color) and the condenser is Mahle-Behr (according to FCP)

[0-60motorsports]

How are you getting the a/c pressures? Hooking up gauges under the hood? Are the pressures high even from the start?

FCP shows this is the compressor for a prod date from 09/02. I’m pretty sure Denso is the OE for BMW for a/c compressors. https://www.fcpeuro.com/products/bmw...em-64526936883

Does anyone know who is OE for the condenser and drier? I think the drier is Rein (based on sticker color) and the condenser is Mahle-Behr (according to FCP)

Hooking up gauges, correct. The pressures are perfect but as soon as it hits 94c coolant temp they start climbing along with the condenser getting hot. Still blows cool Air.

The link you posted for the denso compressor might be wrong for my car as it was produced after 09/02. I checked on the etk with my vin today and this is what comes up (highlighted in yellow):

[8000RPM]

My vote still goes to the radiator.

Ding, ding, I think we have a winner!

I finally got the radiator swapped out this week and order seems to have returned. Warms up to the middle and doesn’t move! The coolant was nice and clean coming out but it must have lost a lot of efficiency.

[FBloggs]

Fingers crossed.
I was beginning to suspect the a/c electrics and sensors..
In simpler days a poor ground in an electrical component, would affect gauge readings in the dash.

[0-60motorsports]

Ding, ding, I think we have a winner!

I finally got the radiator swapped out this week and order seems to have returned. Warms up to the middle and doesn’t move! The coolant was nice and clean coming out but it must have lost a lot of efficiency.

Excellent. Still investigating mine

[0-60motorsports]

Update:

So today we might have discovered the cause of the overheating. Message from my tech who has been working on my car for more than 14 years:


“Bro, something unbelievable in your car M3, I told them to keep the car engine running while under the sun, they did yesterday and when about to overheat put the battery jump start cable that connected from another car that the engine is running then it solve the overheating, the possible cause is weak alternator, the voltage is ok possible the amperage is low and due of a/c load the aux fan became not efficient to push more air.”

New valeo alternator ordered from FCPeuro.

[0-60motorsports]

So here’s an updated after installing a new valeo alternator and new original bmw waterpump, the car is running much better the amps have not gone up too much. Before the new alternator it was putting out 40amps and now around 79. I have another m3 here with 11000 miles and puts out above 100 amps.

The car now runs cooler in today’s 44c temps it was running 88c coolant temps so that’s normal
But when you go past half way mark on the blower fan it starts going up in heat back to around 96-98c coolant temps.

Any ideas guys? The only thing I haven’t changed is the ac compressor and I really don’t want to lol.

[Icecream]

So here’s an updated after installing a new valeo alternator and new original bmw waterpump, the car is running much better the amps have not gone up too much. Before the new alternator it was putting out 40amps and now around 79. I have another m3 here with 11000 miles and puts out above 100 amps.

The car now runs cooler in today’s 44c temps it was running 88c coolant temps so that’s normal
But when you go past half way mark on the blower fan it starts going up in heat back to around 96-98c coolant temps.

Any ideas guys? The only thing I haven’t changed is the ac compressor and I really don’t want to lol.

How's your radiator cap? I ask because my expansion tank sprung a very tiny leak and now my needle will move past halfway under conditions you mentioned. Doesn't really loose coolant but can't hold pressure.

[0-60motorsports]

How's your radiator cap?

New expansion tank should be here in 2-4 days. Ships tomorrow from Europe but the current one is absolutely fine. Still doesn’t explain when we fed the car juice from a running cars battery the temps dropped in under 5 mins and the low miles m3 parked next to mine putting out more than 100amps of power and mine is around 78 amps with a new valeo alternator.