A/C Troubleshooting to Cooling System Issues

[BillyBob78216]

The A/C problem I posted about yesterday tagging onto someone else's post, has developed from bad to far worse. So I decided to post a new thread:

I haven't had the Z very long, into my 2nd year now. Bought in in Nov 2010, and it had decent cooling power then. But it was the late fall, so I wasn't all that about A/C.

The spring 2011 I noticed not much cooling power at all, and by June I decided to top off the system with a can of R134a found at AutoZone. Good results all summer long without any further adjustments. I have a 2nd car so I used it more during these hot Texas summer days.

Again this summer 2012 I parked the Z only because I felt I didn't need to rack up the miles in the heat. I'd drive it only once a month or so. Last weekend I felt the want to drive it, so I washed it nice, and the A/C functioned just fine on Monday and Tuesday this week.

Yesterday something changed. The system started blowing hot air after the car was running for over 10 minutes! I checked that the A/C was indeed on and recirculating. It was a hot day 103 degrees. Anyway I parked it in the work garage, and by then it was blowing cool air again. Hmmmm. When I turned off the car, I noticed a whirling sound, and traced it to the compressor.

On the way home, a 20 mile drive, I noticed the A/C would fluctuate from cool air to hot. The temperature gage was straight up between hot and cold. I got home into my driveway and powered off. Got a burst of steam from the front end. Lots of cooling fluid was draining, with a good amount of steam from the expansion tank area. I allowed it to cool, and the sun go down later to work on it.

I tore out the radiator assembly and didn't see any cracks anywhere in that plastic expansion tank/radiator assy. Tried to leak test it myself, but the leak was elusive. The hoses looked ok too.

So the radiator is now in my trunk of my other car, thinking of taking it somewhere to be checked professionally. The expansion side of the radiator is definitely where all the steam was coming from. Before I tore it down, I filled with water and did see dripping, so something was leaking somewhere.

I pulled the fan blades, allowing removal of the thermostat housing assy. Over the past winters the car never blew hot air, so I know that thermostat must be hung. I bought a new one a long time ago so now is a good time to replace that, and all the hoses and belts too.

I can now access the compressor. Turning by hand, it certainly doesn't sound good. Reading my Chilton's, I'm not so sure I want to do the A/C work, despite all the folks here talking about it could be done by the weekend mechanic. I think the compressor itself will be $800 parts alone right? Not including a system flush, or other component replacement. So I figure this is going to be pretty costly. Better save up my pennies.

I can't see how the two problems could possibly be linked. Do you?

[BMWBergy]

So you've been driving for several years with a non-functional thermostat? I don't mean to judge, but it sounds like you've been neglecting your car, and these failures were only a matter of time.

You should really consider taking the car to a BMW/Indie mechanic and getting Inspections I and II done - like ASAP.

[BlackjackM]

I have heard that one of the initial indicators of an overheating engine is losing A/C coolness, so they may very well be related.

[mpire]

Strange. I don't see how the air conditioning is even related to the engine in any way other than the belt turning the compressor.

Get an aluminum radiator and do the cooling system overhaul. It is quick and easy once you have the parts.

Then we can talk about servicing the a/c

[BMWBergy]

Strange. I don't see how the air conditioning is even related to the engine in any way other than the belt turning the compressor.

Get an aluminum radiator and do the cooling system overhaul. It is quick and easy once you have the parts.

Then we can talk about servicing the a/c

They're all aluminum, aren't they? Or are you referring to one with AL end-tanks in place of the factory plastic?

He's right, though. Radiator, new thermostat, water pump, hoses, coolant, coolant temp sensor all required for a good overhaul. Parts will cost you ~$300, and you can do this in several hours in your garage if you are a competent mechanic - or have one to assist you.

Once that's done and you no longer have a questionable cooling system with a bad thermostat, you can diagnose the rest... you won't be able to do it properly otherwise.

[dreamrider01]

Compressor - do an e-bay search. You'd be surprised how low a refurbished/used one can be.

System - A good idea, particularly if you have more than one vehicle, is to invest in a set of A/C gauges system. They run about $50-$60.

Questions:
- do you see ice forming on the low pressure side after the system has been running for a while?
- is your high pressure side blistering hot during operation?
- if you already have gauges, what happens to high and low pressure when you turn the system off? No change? Do both go up? Only on side goes up? if so, which?

If you decide to change the compressor, may as well do a full system flush, and replace the dryer and OT (if these bugs have them, that is).

M.

P.S.: I wouldn't recommend just adding 134a without knowing what your pressures are. Also, if replacing the compressor it is best you get one that is "pre-loaded". That means that it has been correctly filled volumen-wise with the A/C system oil. Alternatively, if you have to load it yourself, make sure that you get the right type of oil (PAG-???), as well as fill it to the exact recommended volumen.

[Blacklane]

If I already had the fan, shroud, and radiator out, and I knew I had a bad compressor, I would certainly replace that at the same time. Not that it's too bad of a job to replace it from the bottom, but getting to the bolts on the lines is kind of tricky. Then I would pull off the headlight and replace the receiver/dryer and then take it somewhere for a vacuum/recharge. Actually that is also an easy job, but you have to rent or buy the equipment. The refrigerant capacity is on a green sticker under the hood. It also take about 6oz of PAG 100 oil, but I usually measure what comes out of the old compresser, plus a little more. Often failing compressors introduce particles into the system that clog the expansion valve. Luckily BMW put the receiver/dryer in front of the expansion valve, so any chunks from the compressor will get caught there or in the condenser, where it's not a big deal.

Getting back to the cooling system re-condition. For real peace-of-mind, you want to replace everything made of plastic: thermostat housing, fan, expansion tank, radiator, and cap; everything made of rubber: radiator hoses, expansion tank hose, and both belts; and everything that spins: water pump, idler pulleys, and now compressor.

[BillyBob78216]

Took the old radiator to a radiator shop for leak testing. They said the radiator was intact but the expansion tank def was leaking.

I pulled apart the expansion tank and replaced the gasket seals, both upper and lower parts from the BMW parts shop about $20. Still leaks. Pulled it apart again and applied a $5 silicone gasket sealer. Gave it a day to set then watered up. Dammit! Still leaked.

Pelican Parts had some great prices... Don't mind too much that they aren't BMW. $156 for the Bher radiator ... cost double that for an authentic one. Came as a complete assembly with the expansion tank. Just needed to move the sensor into the new rad.

Replaced in but 30 mins. Took a lot longer to fill and bleed. Ran the engine for about 30 mins satisfied no leaks from the new rad or the new thermostat that I threw in too. Nice action there, the temp gage actually raises to the center now ... I will have heat this winter!

Decided to turn on the A/C. Clutch engages... Good... Oh oh chirping getting louder and even louder still! Thought that compressor was going to blow so I turned it off. I knew that was going to be needed to be replaced.

Dropped the hood and the ragtop and tooled around for a bit. Oh oh CEL! Now have to trouble shoot that lol!

It's no biggie working with the cooling system on this car. When I do the compressor I will definitely rip out the cooling system again to easily gain access to it.

[Blacklane]

You don't have to remove any of the cooling system to work on the A/C compressor. Just remove the bottom plastic splash shield and the right headlight. Maybe the washer fluid bottle, I don't remember (it's just one screw anyway). Lots of room to work then.

[BillyBob78216]

I've been driving now a couple of days, and without the AC it really is a drag. Of course I take down the ragtop, and that is cool. But sometimes the Texas sun is just too much.

Thinking about to do this AC job DIY and I'm determining if I can find it even economical for me to do it or farm the job out. There's a shop called BRING YOUR OWN PARTS here that I have used before, saving crazy parts prices. Goodyear changed out a compressor in my Pontiac last year costing me $1,200, a nasty sting in my wallet there's some motivation to DIY.

Compressor - do an e-bay search. You'd be surprised how low a refurbished/used one can be.

Pelican Parts $471.25 New Behr. Must purchase drier separately, $32.75 New Behr.

eBay $199.99 Reman BMW, includes drier.

I wouldn't go less than remanufactored, and a 300 clam savings does sound good, also keeping within BMW branding.

System - A good idea, particularly if you have more than one vehicle, is to invest in a set of A/C gauges system. They run about $50-$60.

eBay $66.99 I think I like this one, comes with a case.

Questions:
- do you see ice forming on the low pressure side after the system has been running for a while?

No ice noted.

- is your high pressure side blistering hot during operation?

Are you asking to handle the hoses to find out? I think I'll pour some blinker fluid and see if it boils off. Seriously I haven't checked this.

- if you already have gauges, what happens to high and low pressure when you turn the system off? No change? Do both go up? Only on side goes up? if so, which?

No guages yet in my toolbox, but soon enough.

- If you decide to change the compressor, may as well do a full system flush, and replace the dryer and OT (if these bugs have them, that is).

The compressor is going for sure. I will replace the dryer too, but what is the OT? Will need to look up what a Full System Flush procedure looks like.

I figure I could use an AC Vacuum too:

AC Vacuum Pelican Parts $59.50

eBay $24.99

P.S.: I wouldn't recommend just adding 134a without knowing what your pressures are. Also, if replacing the compressor it is best you get one that is "pre-loaded". That means that it has been correctly filled volumen-wise with the A/C system oil. Alternatively, if you have to load it yourself, make sure that you get the right type of oil (PAG-???), as well as fill it to the exact recommended volumen.

Pelican doesn't mention if it is pre-loaded, while the reman does. This only makes the reman more attractive.

So far if I was to do myself roughly $300, not including (X number) cans of R134a. I could be missing something, so i put it out here.

They're all aluminum, aren't they? Or are you referring to one with AL end-tanks in place of the factory plastic?

The expansion tank is always plastic, or at least I don't know if there is an all aluminum version.

He's right, though. Radiator, new thermostat, water pump, hoses, coolant, coolant temp sensor all required for a good overhaul. Parts will cost you ~$300, and you can do this in several hours in your garage if you are a competent mechanic - or have one to assist you.

Expansion tank seals, upper and lower $20 Geniune BMW. Waste of money, did not work to seal leak. Ended up with purchasing new radiator that included these seals with a new expansion tank.

Radiator, Behr $154.75 from Pelican.
Thermostat, Behr $89.99 from O'Reilly Auto Parts. Paid too much, Pelican sells for $50.50
Coolant $14.50 Peak Long Life. I figure I'd buy the Geniune BMW after I am certain no leaks. Besides I'll probably be doing the AC or the Water Pump anyway soon.
Belts, Dayco $47.98 from AutoZone. Both belts looked overdue. Probably overpriced too, but I didn't find both belts available at Pelican.
Rivets, BMW 4 x 0.75 Needed to replace as they get destroyed in removal.

I could have easily justified replacing the hoses but I think they looked replaced recently and in good shape. The chrome BMW clamps cleaned up nice and were reused. Didn't replace the sensor or the water pump yet either, yes I know the pump is a ticking time bomb.

Once that's done and you no longer have a questionable cooling system with a bad thermostat, you can diagnose the rest... you won't be able to do it properly otherwise.

Now that I have a sealed system again, and even a good thermostat for the first time in this car, it is quite worrysome watching that gauge now, because it never before left the blue zone. Now the gauge reads quickly dead center. Today while at idle waiting for a train to pass, I watched the gauge rise just a tad to the right of middle which worried me for a moment. As soon as I was on my way again, the needle returned to its home in the center.

Ready to move on to the AC repair.

[Blacklane]

For a compressor job, I would replace the compressor and receiver/dryer. Inspect the compressor and lines for signs of debris. If you find that the compressor has disintegrated and left debris in the lines, you're going to have to disassemble the lines and clean them with line cleaner available where you buy refrigerant. You will have to remove and inspect the expansion valve, since all debris collects there.

Replace the oil with PAG-100. Measure what comes out of the old compressor, plus a little more. The entire system uses 6 oz, so you should need a little less than that.

Evacuate the system for an hour or so.

There is a green sticker under the hood that specifies the amount and type of refrigerant to use. I use a cheap digital scale from Harbor Freight to measure the weight of refrigerant I'm installing. Once you have enough refrigerant in the system to allow the compressor to start, run the engine at 1500 RPM to suck in the rest of the refrigerant until you have installed the required amount, and no more. Watch the gauges and you should end up at about 35 low and 225 high inches of mercury (inHg), give or take depending on temperatures and RPMs.

[PatAz]

I had this condition fixed with a new compressor and dryer installed.