Hey guys, its getting past 100 degrees here in Texas, so i figured its time to look into the non functional AC. Its a 88 series3, v12 and has been converted to R134.

Put manifold gauges on it, zero!. So much for POs "just needs topping up".
Connected a vaccum pump, wont hold vacuum for more than 30 secs.. so my usual approach of using a electronic sniffer is not gonna fly. Can not see or hear any visible leaks, looked at all hoses and joints. The exp valve barely visible behind the v12 shows signs of some putty like soft flex material covering it. I assume thats PO's attempt at sealing, surely its not stock, right? See pic..

Any suggestions for conclusively tracking the leak or known weak areas? That exp valve looks like a bugger to get out, I'm praying its not that. If i have to throw parts at it, i suspect that will be the first candidate?

 

Not being picky but you might be on the wrong forum here.
If you are running a Series III (XJ12) then you might get better help on that group.
Whilst there are obvious similarities with the V12 setup there were detail changes, especially with the Van den Plas models.
Anyway, it's 117 in Egypt, what are you complaining about!

 

Putty at the expansion valve at the firewall? That's not unusual, my car has putty sealing up the hole where the lines run in.

Why don't you put in the UV dye and see where it shoots out? That's what any shop is gonna do.

 

It's not a sealing putty. it's heat insulation. Common.


http://cdn3.volusion.com/klmat.yytxn...jpg?1425797380

Cheers
DD

 

If it won't hold a vacuum, an A/C specialist would probably fill with Nitrogen to find a leak like that.

Paul

 

Get a can of R134A that contains dye, and get an ultraviolet inspection flashlight. The refrigerant with dye is only a little more expensive than regular refrigerant, and I got a decent UV flashlight for about $12 on ebay. Shake up the can to mix the dye and put a little into the system, use the flashlight to find where the dye comes out. Once you fix the leak you can put the rest of the 134a/dye into the system so if you spring a leak again it will be easier to find.

 

I don't know about the US, but over here it's illegal to put an A/C gas into the system knowing that it will leak. That's why A/C firms have to use something like Nitrogen if a system won't hold a vaccum.

Paul

 

They sell the dye separately. You can send the dye in and try to pressurize with air, no?

You may as well start shopping for a drier now. You'll certainly need that. You can decide whether or not you want to get a new expansion valve (not expensive) and start looking for a condenser, just in case. All much cheaper if you buy it on your own.

 

there is no problem changing the expansion valve on either series 3 or xjs, just need the correct assortment of tools, if its gassed loosen the valve and leave it over night to drain out it would go in the atmosphere if you had a leak so whats the difference? but not good for your eyes evidently.

 

If the leak is that bad, you'll be replacing the drier and evacuating the system anyway, so just plug compressed air into the system to find the leak.

 

Thanks, thats the direction that seems logical to me as well, don't want to wantonly release R134a into the atmosphere, so dyes and sniffer are out. Will put some new Schrader valve cores and pump it up gradually and check with soap water if i don't hear any hissing.

So the putty is, er, was stock, huh?

 

I realised after I had posted that Vee had already mentioned using compressed air as well. Personally, I'd just plug the air into it, regulated to say 50pis and test with the air on, then you are sure the system is staying pressurised as you search. It sounds like a decent leak.
A leak sniffer should still detect a compressed air leak if it is an ultrasonic type detector. If not, the old soapy water works just as well as anything fancy, it's just messier!
The putty is fitted to all A/C systems, it serves to insulate the TX valve sensor from engine bay heat to get a more correct reading of the gas temp from the valve. I can't recall owning a car that didn't have the putty.

 

Hi , What tools are needed to replace the expansion valve on XJS V12 1990 please ?