I'm replacing the AC expansion valve while everything is apart as I am upgrading the system to R134a. I note the old (original) valave had a plastic cap on one end with some insulating material, but the new one doesn't come with one. Unfortunatly the old cap doesnt fit on the new EV (its too big) so before I fabricate something does anyone know if the cover is really required? Various photo on the forum show some EVs fitted with a cap and some without.

 

That's a shipping/storage cap. Invest no worry in it.

 

Thanks. Surprised to hear that as the PO left it on for 33 years.

 

Not a shipping / storage cap. The expansion valve is thermostatically controlled and adjusts to the temperature of the system with the help of a diaphragm and a small capillary tube. The cap is there retain the insulation which prevents thermal influance from the ambient environment having a undesired influence / effect on the performance of the valve.

 

Thanks! I'll see if I can make the ID of the old one smaller so I can use it

 

Send me the exact OD of the ring it fits over, in thousandths of an inch, and I'll make you one. Then PM me your address.

 

That's very kind of you but I managed to source one locally (I'm in the UK so postage would have been too much trouble for you)

 

Darn, I already had it designed in my head. The only problem I was concerned about was the size - - whether it is too small to fit over the inside points on the jaws of my three jaw chuck in my lathe. I even have a nice chunk of black plastic that I think I could make it out of. I send a lot of stuff the the UK, so no big deal on the postage.

 

Jerry--

Great to see you back in the group!

The Behr replacement/spare I have (in original Porsche packaging...) has no insulation or cap around the diaphragm. Installed, the while expansion valve may or may not have insulation around it. Mine had none originally, A few that have passed through have been wrapped in gluey foam that had rotted with age/heat. The cap tube "samples" heat on the low-pressure port, and that typically ends up being about the same temp as the aluminum valve body. The diaphragm sits at the same end, so housing temp at that end will be about the same as what the probe end of the cap tube sees, plus/minus the small change from ambient delta.

Bottom line is that I'm not sure how insulation or no insulation only on the outer end of the diaphragm would make any significant difference in the expansion valve function.


Anyway, back to your regularly-scheduled activities.

 

Just to offer some more data here, my 84 parts car has one of those caps on the expansion valve (thread on style fittings) while neither of my 86.5 cars (which looked to have original? egelhof expansion valves to begin with) did. Neither did the oe replacement I put on my blue 86.5. I've never seen a cap on the diaphragm on any other car that I can think of either.

 

1. What model year 928 do you have? The very early 928's had some significant differences- mainly the compressor model/hoses and conceivable that the expansion valve on those models was also different but i do not know that for a fact.
2. Not all expansion valves are the same. Your picture tells us you have a Behr packaged item made by Egelhof- was that offered as a confirmed 928 spec part or is it something that fits but not necessarily the 100% correct item? We have had recent examples where expansion valves were supposedly for the 928 but under performed and then the same system worked well when a part supplied by one of our recognised parts gurus was installed.
3. For all S4/GTS variants non were supplied with any kind of cap in the position shown. The disc assembly on the end of the valve is the actuator for a spring loaded needle valve of some kind. There is a bulb inside the valve wherein under certain conditions the liquid vapourises- this creates a pressure that passes through the capillary tube and moves the diaphragm. The external equilibrium conditions in the area are more or less constant on any given day so difficult to visualise why any kind of insulation would be needed. If such were needed it would have been supplied with the valve and such is just not the case.
4. The first and only 928 supplied with R134a was the GTS and even that model was originally supplied with R12 on models such as mine until some time around mid 93 I believe. The expansion valves for both systems have the same Porsche part number in PET.

 

Hello the car is an 85 so will have originally run on R12 which isn't sold in Europe anymore so am upgrading so R134a and the Behr EV you see was the correct 134a one specified for the car. I'm rebuilding the car pretty much from the ground up (talk about mission creep!) and in the process have replaced all the AC hoses, drained the miniral oil out of and resealed the compressor, and will be fitting a new condenser and dryer once the engine is back in

 

As I am aware the evaporator is the same as later models not sure about the condenser. Maybe a kind soul can confirm the situation. It is one thing being told it is the correct valve it is another knowing for sure it is. Perhaps you can advise the source of your info.

A closer squint at your photo shows the valve to have been made in China. As I am aware genuine Egelhof valves are made either in Germany or France so that raises some doubt as to whether it is a knock off component.

 

It was bought from a reputable parts supplier so it's certainly not a knock off. Many western brands have factories in China nowadays so I don't think that really matters.

 

Last time I checked Egelhof had factories in France and Germany- possibly the States as well. They may well have opened a factory in China as well- that is not really the issue- what matters is that it has the correct spec. We have seen listers with alleged credible sources but unless it came from Richard [Ritech] in the UK or the likes of Roger and our other specialist 928 suppliers in the States I ten to be a bit suspicious of the supply line until I have good reason to be confident which you may well have.

Presumably you will be changing all the O rings with the correct spec for R134. Presumably you have migrated to the correct barrier hoses. I trust you may also be changing the third captive hose whilst the engine is out- that thing is a sod [nigh on impossible?] to change out with the engine in situ.

Sounds as though you are going about things with appropriate diligence.