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Discussion Starter · #1 ·
I have a 2000 328i sedan with 5sp MT (276k miles). The a/c works fine after initially driving the car and continues cooling well with no issues (even with extended driving) unless I stop and park the car for running errands (I.e trip to grocery store, etc). When I start the car again after being in the store for a short time, the A/c doesn’t provide cool air (some very minor level of cooling, as turning off ac makes it even hotter). Once the car sits and completely cools, a/c works great once again. Any ideas? If refrigerant was low, I wouldn’t expect good cooling when initially driving the car even on hot days. Could it be overcharged and causing the high pressure switch to stop the compressor once refrigerant heats up from the hot engine while shut off? Radiator cooling fan is running and coolant temp gauge remains “normal”. Back in July, I added ~8 oz of R134 due to poor cooling and everything seemed fine. After AC charge, I achieved the following numbers: ambient temp = 86 F; suction pressure = 40 psi at idle & 32 psi at 1500 rpm; discharge pressure =245 psi at idle & 275 psi at 1500 rpm; vent air temp = 57 deg f. Looking for help, as the issue seems to be getting more frequent. Thanks in advance for hanging in there with the long post and any potential feedback.
 

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E30M3 Race F10 535 R1150Rt M Coupe
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Some good clues and I tend to agree that the pressure side of things looks near normal.

I would try two things to get some better clues:
Scan the IHKA module for faults.
Take a pressure test (again) but when it's acting up.

Thoughts: Evaporator temp sensor getting wonky? Blend door not working properly? Heater control valves not 100%?
Pressure spikes? (Real and/or faulty pressure sensor?)

I would want to KNOW what's going on BEFORE I replaced any part.
 

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2006 330 Convertible
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This may sound stupid, but have you checked your coolant level? My 323 had a pinhole leak on the top of the radiator that went undetected for over a year. I checked several things including having it pressure tested by a highly regarded local indy shop, who found nothing wrong. But every time the coolant got down to a certain level in the radiator, the AC lost its' cooling power. After it was topped off, everything was fine until the level dropped again. Driving it with stop and go driving caused the coolant loss. Highway driving caused no issue. I drove it 6 1/2 hours of highway driving to NY & PA and the same back with minimal coolant loss.
 

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Discussion Starter · #4 ·
This may sound stupid, but have you checked your coolant level? My 323 had a pinhole leak on the top of the radiator that went undetected for over a year. I checked several things including having it pressure tested by a highly regarded local indy shop, who found nothing wrong. But every time the coolant got down to a certain level in the radiator, the AC lost its' cooling power. After it was topped off, everything was fine until the level dropped again. Driving it with stop and go driving caused the coolant loss. Highway driving caused no issue. I drove it 6 1/2 hours of highway driving to NY & PA and the same back with minimal coolant loss.
interesting. I have had slow coolant loss. I see coolant staining around the expansion tank which makes me wonder if my cap is leaking when hot and under pressure. I just filled it a few days ago, but coolant was not low enough to set off the low coolant light. I will have to check with a short stop and see if I have poor ac cooling now that the reservoir is completely full.
Some good clues and I tend to agree that the pressure side of things looks near normal.

I would try two things to get some better clues:
Scan the IHKA module for faults.
Take a pressure test (again) but when it's acting up.

Thoughts: Evaporator temp sensor getting wonky? Blend door not working properly? Heater control valves not 100%?
Pressure spikes? (Real and/or faulty pressure sensor?)

I would want to KNOW what's going on BEFORE I replaced any part.
Thanks for the input. How do I check for IHKA faults? I will check compressor pressures when the issue occurs again.
 

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2006 330 Convertible
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interesting. I have had slow coolant loss. I see coolant staining around the expansion tank which makes me wonder if my cap is leaking when hot and under pressure. I just filled it a few days ago, but coolant was not low enough to set off the low coolant light. I will have to check with a short stop and see if I have poor ac cooling now that the reservoir is completely full.
My coolant loss was slow as well. I had the same coolant staining up top around the expansion tank & upper radiator hose. I replaced the expansion tank and cap which did nothing. The Indy shop replaced the upper hose which also did nothing. I've never done pressure testing, but I would guess that they do the pressure test with a steady throttle which mimics highway driving which is why it showed nothing. Maybe a UV/dye test would show the problem if the scan MrMCar recommends does not pan out.
 

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2016 340i xD 6-spd
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interesting. I have had slow coolant loss. I see coolant staining around the expansion tank which makes me wonder if my cap is leaking when hot and under pressure. I just filled it a few days ago, but coolant was not low enough to set off the low coolant light. I will have to check with a short stop and see if I have poor ac cooling now that the reservoir is completely full.

Thanks for the input. How do I check for IHKA faults? I will check compressor pressures when the issue occurs again.
You know your ET shouldn't be completely full...if that's what you really mean. The coolant should be between min and max when cold...or 5.5" below the top of the filler neck. You need air in the ET or it isn't an ET--when coolant gets hot it expands and needs a place with air to expand into in a closed system.
 

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Discussion Starter · #7 ·
You know your ET shouldn't be completely full...if that's what you really mean. The coolant should be between min and max when cold...or 5.5" below the top of the filler neck. You need air in the ET or it isn't an ET--when coolant gets hot it expands and needs a place with air to expand into in a closed system.
yes, I was filling until the float stick raised up to the max mark. Definitely not filling the reservoir completely full.
 
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