Hello,

I'm a new owner of 85 Vanden Plas and I'm getting familiar with the car - and its problems. I have an oil leak that appears to be originating from the plumbing to the cooler show in the attached picture.

I cant' find this part in any catalogs or manuals - though I admit I may not be looking in the right places. Its attached to the freon compressoer and has the evaporator outlet plumbed to the forward side and then the freon exits to the rear and into the compressor. What appear to be lube oil lines are also plumbed to it. One comes from the lower rear of the engine and the other exits and runs up to the front under the intake manifold and appears to then enter the back of the head. So my guess is its purpose is to cool oil being fed directly to the cams?

Anyone seen one of these before? I've worked on lots of cars and never seen anything like this. My A/C system is inop so it can't be providing any cooling - and at any rate would only provide cooling if the A/C were running.

Thanks, Ben.....

 

That's a fuel cooler.

Unused fuel goes thru the cooler and then back to the fuel tanks. If you look closely you'll see that those are fuel hoses. One side eventually goes forward and upward to the front of the cylinder head and the other goes down an rearward toward the back of the car.

The climate control system is designed so that the compressor runs in all modes....even when heating is called for. Thus, fuel is always being cooled. Providing, of course, the system is operational, as you say



Cheers
DD

 

Also seen in your picture are the power steering hoses....which might be the source of your oil leak.

And you can also see the air conditioning pipes/hoses....which, if leaking, can drip a bit of refrigerant oil


Cheers
DD

 

Thanks, Doug. I now see similar fuel coolers listed on parts sites, but its difficult to find this exact part in the catalogs. Who has the best catalog or is there a good on-line parts manual (1985 Vanden Plas)? SNG Barrett seems to have a good on-line catalog but doesn't show this part.

I'm gonna have to do some more searching for the oil leak. I may reorient the pipes/lines exiting the cooler anyway as one of the fuel lines is hard up against a refrigerant line (below the blue cap) and I'm concerned it'll rub through. Fixing the A/C is high on my list so now's a good time to be loosening fitting and making things right.

Thanks again for the quick reply.

Ben....
Columbus, IN
1985 Vanden Plas

 

I suggest buying an actual Jaguar parts catalog. Look up your parts then Google the part numbers you need. Plus, the illustrations are very useful when working on the car. Money well spent

79 87 Jaguar XJ6 Parts Manual Catalogue Book XJ 6 Series III 3 XJ 6 1985 1984 83 | eBay


Cheers
DD

 

Thanks for the link. I've used digitized versions of factory pubs before and the paper is handier, but also pricier. I spent some time under the car today and found the hoses to the transmission cooler appeared to be the major source of the leak. I replaced those and will now wait to see how much of the leak that clears up.

The front crank seal and oil pan gasket looked pretty dry and I didn't see any major leaking from the head or valve cover area so I'm hopeful that was most of it.

Thanks again,

Ben Z....

 

Well, I thought I'd provide a quick update.

Replacing the tranny cooler lines stopped any leaks from there, but it was still leaking.

Then I loosened and replaced the fuel line exiting the cooler and reoriented the cooler and A/C line so they didn't rub. There was a pretty good divot in the rubber fuel line. The fuel spilled during that work cleaned up the area below and made it clear the PS lines weren't leaking.

That leaves the A/C. It wasn't working anyway, zero pressure in the system, but the compressor clutch still engaged. Is the no low pressure cut-out switch? I can't see the exact source yet, but once I disconnected the compressor clutch the leak stopped. I am going to pull and replace the compressor and have the lines upfit with new R134a hose while I'm at it. Hope to get that done before warm weather hits.

Ben.....

 

There should be a 3-prong thermal fuse clipped to the compressor bracket. When the 'superheat' switch in the back of the compressor closes then the circuit is grounded and the thermal fuse blows, cutting power to the compressor. Perhaps this has been bypassed or removed on your car?

Later cars (late 1987 model year) went to an "HSLP" (High Side Low Pressure) switch system. This eliminates the need for the thermal fuse. Sometimes when compressors are replaced the "Superheat" type is replaced with the "HSLP" type. Either way, though, the compressor should not operate when there is no pressure....so something is bollixed up as you obviously suspect

Cheers
DD

 

Doug,

Thanks, I'm familiar with that type of system. My TR8 had that style plus a Ranco switch for the electric fan control. I replaced both with a trinary pressure switch that did the low pressure clutch cut out and the high pressure fan cut-in. Looks like installing a low pressure cut-out switch in the compressor will be simplest here since fan control isn't necessary.

Regarding fan control though, I see there is an auxiliary electric fan. Is that coolant temp or freon pressure controlled? From reading through the manuals it looks like its coolant temp controlled from a temp switch in the water pump housing?

Ben.....

 

It is temperature controlled only. The switch is radiator mounted, RH radiator tank, hard to see and reach. It closes at about 94ºC.

Some of the Jaguar diagrams/manuals suggest a tie-in with the compressor circuit but in reality only the V12 cars were built that way. And it's the V12s that have the temp switch mounted in the pump housing

Cheers
DD

 

Doug,

I did a little investigating about how to replace the current superheat switch setup on my '85 VP with the later high pressure switch setup. Ran across this "how to" from 4Seasons (attached).

One assumption I'm making is that the mounting bracketry didn't change from '85 to '87. Do you know if that's true? I know these GM A6 compressors were largely the same, but that there were some differences. The 4Seasons 58096 with a high pressure switch is what is listed for the '87 and the '85 on RockAuto while some of the other brands specifically list w/superheat models for '85. This leads me to believe they're interchangeable except for the type of protection circuit.

The biggest advantage I see for getting rid of the superheat setup is that I won't have to replace the fuse every time its low on freon. Also, the non-superheat models are quite a bit less expensive - I'm guessing just because they're more popular.

Ben.....

 

I have that same document

Jaguar went to the HSLP switch towards the end of 1987 model year. VIN 471xxx or something like that. Don't draw any firm conclusions from the parts listings from Rock Auto and the like. They have things all bollixed up.

HSLP vs. Superheat compressors have different end plates at the rear. AFAIK the end plates can be swapped in either direction. Mounting-wise the A6 compressors are interchangeable with metric vs. non-metric fasteners being the only difference I'm aware of.

Watch for different pulley sizes....but even then a simple belt change is all that's needed to makes things work

Yes, the HSLP system makes more sense

Cheers
DD