Automotive Air Conditioning Information Forum

I replaced the condensor, compressor, receiver, expansion valve and some (not all) lines on my '89 BMW 325i as part of a R134a conversion. It cools well when charged but looses a charge relatively quickly - within a day or so. I have tried UV dye and a "sniffer" but have failed to locate the leak.

I suspect it may be the old rubber hoses. Is is common for these to leak on older cars, and does the R134a exacerbate this? I

Any other tips for finding leaks?

That is a significant leak. You should be able to find one that big with soapy water.

If there is no dye or hits on the sniffer under the hood, you need to check the evaporator. Try the sniffer in the vents inside the car.

I did give the vents a solid sniffing, with the A/C running, just after it was off etc. I'm a bit at a loss...

I have nearly zero experience in this, but I'm interested to hear what you learn. I thought I had read that you need to upgrade the barrier hose on older cars to make sure R134a doesn't leak through. According to this article, freon may leak through that a sniffer and UV dye will not detect: https://griffiths.com/mr-ice-project/ba ... e-upgrade/

Are you sniffing while the engine fans are running? Maybe leave the engine off while you use the sniffer so the freon isn't being blown around/away from the leak point or diluting the readings.

When you test at the vents, do you have the ac blower on low? I wonder if the blower is moving so much air it's diluting the leak and preventing it from being detected.

Have you checked the sniffer to make sure it's able to detect freon? Maybe you could test it by releasing some freon from a can to make sure it's working.

It seems logical to me that if the UV isn't visible under the hood it is probably leaking somewhere hidden under the dash or through the hoses themselves.

Perhaps you should try that sniffer on a known refrigerant source.

A leak that large would be hard to pinpoint with a good sniffer - it might go off at the grille with the hood closed.

As for the Porsche site nonsense - no. He is selling an upgrade.

Barrier hose is somewhat better, but an '89 probably already had lined hose. It came in to play in the mid 80's.

You have a gross leak if you lose 12 ounces in 48 hours.

Leaks can be evasive at times. Try sniffing the drain tube after the vehicle was running, put a plastic bag around the front of the compressor. The size of your leak should not be that difficult finding. Do not put your sniffer at the opening of a can of refrigerant. Too much refrigerant will trip it off and not give you an accurate indication if it works or not. A better way is to hit the Schrader of a second and after a minute or so, try the sniffer. A Schrader will usually show a hit with a good detector without releasing refrigerant. Schraders are not designed to stop all leakage...the caps are the final stop areas.