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#1
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AC Overhaul
Symptoms: AC feels normal at low ambient temps (<70F or so). Once it gets warm, the driver side blows roughly ambient temp air and the passenger side blows may 10 degrees cooler. Refrigerant sniffer detected a slight leak in the vents, suggesting an evaporator leak. First thing: evacuate the AC system. Took it over to a buddy's house who has a refrigerant/AC cert to recover the R134a. With engine off, the low side was measuring 75 PSI. On engine startup, the low side was ~25 PSI and the high side was ~250 PSI. After shutting the engine off again, pressures went to 50 PSI and 200 PSI. Buddy suggested that could be an indicator of crap at the expansion valve, which is an indicator the pump is going bad. As of the time I am starting this thread, the dash is out, and I've removed the heater lines and components from the engine bay. Looks like someone has been under the dash once before as there is some weirdly cut foam around on of the ducts. Can't tell if the blower motor is original or not; it's a Siemens unit and it's been making a super high pitch (almost inaudible) squeal for years. Today's goal is the get the rest of the heater components out and then remove the box for access to the evaporator. |
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#2
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Refrigerant sniffers can be triggered by moisture so many times will show an evaporator leak when there is none so don't be fooled by that.
__________________
1988 325is (purchased new) sold 2004 X5 3.0 2005 X3 2.5 2008 X5 3.0 (new to me) |
#3
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Before the dash removal...how long did it take between refills/recharge the system again with freon?
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#4
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AC Overhaul
Quote:
I tried one recharge at my buddy’s place; the delta was pretty small. Same issue. I recognize the low side pressure read was kind of low based on what I found on other threads around here; might have been worth a quick shot from a 134a can to give ‘er one more go. But here we are. I’ve had a compressor lock up when just recharging with an off the shelf can (I was young and didn’t know what I was doing, but still), so I was wary of just dumping some more refrigerant in. Last edited by nahvkolaj; 10-15-2024 at 09:24 AM. |
#5
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AC Overhaul
Good questions asked so far. In hindsight I probably should have done some more thorough troubleshooting on this forum before committing, making 100% sure I needed to break into the AC system. That said, the car has over 180,000 miles on it and I’ve been putting off replacing that blower motor for years. Now all that I can do is forge ahead, do all this stuff “while I’m in there,” and let this record remain to hopefully help anyone in the future.
This is where I was at when I started work yesterday. Sucks that the dash has to come out for the blower motor, but now that I’m this far I would like to not have to get in here again. Got the box out and got to work. There was a TON of lube oil that dripped out of the evaporator plumbing. It made a freaking mess. Damn near have to completely disassemble this thing to get the evaporator out. Thankfully the box is very clean inside. Previous owners must have kept the cabin air filter in decent condition. The hardware securing the plumbing to the evaporator was in bad shape. New Nissens evaporator prepped to go in. I added the foam around the perimeter myself to try and match the OE unit as much as possible. The unit itself looks damn new identical to the old one; it does not look like it suffers from cost cutting manufacturing. New heater core and expansion valve with pipes are Genuine BMW parts from BMW Northwest. A nice hiss came out of the evaporator when I went to connect the expansion valve and pipes, so it should be in working condition. The block that passes through the firewall is plugged to keep the system clean. Took apart the expansion valve. A little gunky; not sure what passes for “clean” this deep into an AC system. Finished everything off with new sensors, blower motor resistor, and circulation/fresh air door servo motor. Shout out to tacairlift and their post here: https://xoutpost.com/bmw-sav-forums/...ement-diy.html. This helped me know what to expect getting the dash frame and blend box out. |
#6
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I've learned a few key things to do on A/C systems. The recent compressor on mine is blowing ice cold. The cooking thermometer reads as low as 36F.
The weakest and most most common leak points are schrader valves. I replace them. If the system empty, replace the pressure switch. It controls the AUX fan. Replace the dryer. Super easy. Use a bolt threaded into the sock assembly to pull it up. If possible, always use a vacuum test for leaks. A 45 minute vacuum and at least 15 minute hold is sufficient. Recharge a system using a R134a pressure chart. Refill to the low side of pressures. For hot climates, charge to the higher end of specs. Open all the windows when adding R134a. Set the climate controls to MAX.
__________________
'06 X5 3.0i - bought @143,123 miles (12/26/20) |
#7
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Several years ago when I changed out the evaporator and had concerns of sticking vent flaps. I opened the heater box and found goo over the flap edges and rotating points...took butter knife and scraped away the decomposing foam which turned into the goo.
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#8
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One of the ways I found helpful in determining if my evaporator core is leaking was to check under the car after the AC had been running for enough time to drip water under the car. If the system has UV dye in it you'll see it in the water with a UV light. It's faint......but if it's leaking......it'll probably be there.
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#9
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Quote:
The foam in my heater box seems to be in good shape. Not decomposing or crumbling at all. It’s kind of surprising. It’s worth giving everything a second look though to make sure Sent from my iPhone using Tapatalk |
#10
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As part of this project I am replacing a lot of the cooling system hoses that I have reasonable suspicion of being over 10 years old. Unfortunately, it appears PN 6421838353 (HOSE F ENGINE INLET AND WATER VALVE) is NLA. Both ECS and the dealership cancelled my orders. Not seeing an aftermarket alternative too. The hose that I currently have is by Corteco and appears to be in good condition.
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evaporator, hvac |
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