'89 BMW pressure is high

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'89 BMW pressure is high

Postby jsf252 » Wed Jun 29, 2005 10:07 pm

I'm sure you guys get this all the time, but I'm having a problem with my BMW and the coolant pressure building up. I am by no means a professional, but I do have the equipment to do fill an empty system. I own 2 E30 BMWs (older bodystyle 3 series). I've retrofitted them with expansion valves, and reciever dryers for R-134a. One of the cars took the coolant great, built up to ~40psi and stayed there.
My other other one, will take one small can (12 oz.) and then as soon as I connect the second it builds up to 70psi. It's not blowing cold air either. I'm thinking that the expansion valve may have been clogged by some debris in the system.

The simptoms are:

70psi when compressor is runnig
90psi when compressor is off.

would this be consistent with a clogged/malfuntioning expansion valve, or something else?

Thanks in advance,
Josh F.
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Postby DNT » Wed Jun 29, 2005 10:13 pm

Critical to know the high side pressure for a proper diagnosis but just from what you posted I would suspect a stuck open TXV or a weak compressor. high side pressure readings will be neccasary.
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Postby jsf252 » Wed Jun 29, 2005 10:47 pm

DNT wrote:Critical to know the high side pressure for a proper diagnosis but just from what you posted I would suspect a stuck open TXV or a weak compressor. high side pressure readings will be neccasary.


Low = 65psi
High = 65psi

I'm guessing that there is something definately wrong, as the "high" side should be "higher" than the low side. Hopefully you can now tell me if its the expansion valve, or Compressor. My guess is the compressor, as it's probably shot over the years, and I'm sure it has been open to the atmospere since I bought it (last winter).

TXV = Thermal Xpansion Valve???

Thanks,
Josh F.
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Joined: Wed Jun 29, 2005 9:57 pm
Location: Gainesville, Ga

Postby Guest » Wed Jun 29, 2005 11:26 pm

If the compressor is running, and the "wheels" on the manifold set are cosed, then the compressor lost it's valves..A stuck open/closed expansion valve would still give you great variations in pressures. Another possiblity is the key in the shaft broke, making the compressor spin, but not turn the insides..Hope this helps.
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