8 cylinder front engine iconic vehicle
  • User avatar
  • User avatar
  • User avatar
  • User avatar
  • User avatar
User avatar
By aridaen
#141937
Hi,

I'm finally replacing the carpet in my 86.5 and after I removed the rear center console, it looks like the expansion valve has not been replaced. Supposedly, there was a conversion done by a PO, but looking at the valves more closely, it looks original to me. The A/C blows cold, but never seems to cool the car off on a really hot day. Do these valves look like original equipment to you, and should I go ahead and replace them with known 134a compatible valves while I'm in there just to be sure?

Steve D.

Image
Image
User avatar
By NCporsche
#141942
I am not a 928 guy but I know some about automotive A/C. Yes, change it over to a 134 valve BUT only do it after pulling all the refrigerant out of the system (you will lose it w/o this step) and do the 134 conversion.

Check the system to ensure no leaks and then fill with the refrigerant.
User avatar
By worf
#141944
aridaen wrote: Sat Mar 26, 2022 2:28 pm Do these valves look like original equipment to you, and should I go ahead and replace them with known 134a compatible valves while I'm in there just to be sure?
You are asking the wrong question.

The right question is "Should I replace the four o-rings for each expansion valve because they might be original?"

And the answer is yes. Once the expansion valves are on your bench, your original question answers itself.

If you want your A/C to work reliably for 10 years or more then replace:
- all A/C o-rings (25)
- receiver dryer
- Schrader valves (4)
- compressor
- expansion valves

That's about $550 in parts. Alternatively you can save $400 if you have the wherewithal to reseal your compressor.

Along the way, if you find any black o-rings then it you have found additional evidence - besides the expansion valves - that the r134a conversion was done 'on-the-cheap.'

You should also examine the compressor hoses and verify that they are r134a barrier hoses.

If you want your A/C to be as trouble-free as possible. Delete the rear A/C. It's of marginal utility since the 928's A/C system is condenser limited. And the rear A/C provides 50% of the places from which refrigerant can leak. Furthermore, the rear A/C evaporators, at this age, are usually leaking.

Last, if you want to be thorough there's a hose section from the receiver dryer to the engine bay high-pressure line that, again at this age, can be problematic. But, replacing that hose section with barrier hose is an "advanced procedure."
milrad liked this
User avatar
By aridaen
#141964
Thanks for the replies. I do have this receipt in the documentation that came with the car, and I believe this is where the conversion was done due to the evac and recharge listed. When I did the water pump/timing belt in 2020, I pulled the condenser and fan out to clean and paint them and I replaced the O-rings and receiver dryer then. I will go ahead and order new valves and the O-ring kit along with a new receiver dryer.
Image
User avatar
By ChrisZ
#142373
Question to add onto this: Is there any value to replacing the "serpentine" condenser with a parallel flow one?
User avatar
By worf
#142387
aridaen wrote: Sat Mar 26, 2022 7:10 pm Thanks for the replies. I do have this receipt in the documentation that came with the car, and I believe this is where the conversion was done due to the evac and recharge listed. When I did the water pump/timing belt in 2020, I pulled the condenser and fan out to clean and paint them and I replaced the O-rings and receiver dryer then. I will go ahead and order new valves and the O-ring kit along with a new receiver dryer.
Image
Good news is that they replaced the hoses. A new set of those is excruciatingly spendy now.
Last edited by worf on Mon Mar 28, 2022 9:51 pm, edited 1 time in total.
User avatar
By worf
#142391
ChrisZ wrote: Mon Mar 28, 2022 8:59 pm Question to add onto this: Is there any value to replacing the "serpentine" condenser with a parallel flow one?
I can offer no opinion on that.

If you’d like a guess, then my answer is: probably only a marginal increase in condenser capacity for a lot of hassle.

Why?

Look at how the condenser gets cooling air.

Also,

GB’s ‘high output’ A/C system doesn’t replace the stock condenser. It adds another condenser and fan (in the wheel well in place of the washer tank.) If changing the condenser made a difference, I’d bet he’d have done it. (A/C is a big big deal in L.A.)

With the stock setup, your vent temps should below 32°F (until the anti-freeze switch opens). If you feel like your A/C is poor and your vent temps are not that cold then you’ve got more A/C work to do.
User avatar
By ChrisZ
#143387
Fair enough, I put a parallel flow one in the 944S (which has an even smaller condenser) and it works very well on R134 and PAG-100 DEC oil.

The 928S hasn't had the AC fiddled with in 3 years or so now and seems to work well.... enough but I'm always looking for improvement. When under speed one can run the front and rear AC together and get a more balance amount of cooling through the car. And in the winter the rear AC is *great* to defog the entire car pretty quickly.

If you don't have a washer tank how do you wash your windows?
User avatar
By Hey_Allen
#143429
For what is worth, a parallel flow condenser is the only major physical change suggested when updating a MB w126 car from r12 to r134a.

If course flushing out the old oil and replacing seals and potentially a pair of hoses, but the condenser was required to take the swap from being pitifully ineffective bank up to passable cooling efficiency.
That said, the w126 cars had rather poor AC performance even on r12. Reportedly their systems were a bit undersized by design, at least compared to modern air conditioning designs.
User avatar
By worf
#143460
ChrisZ wrote: Mon Apr 04, 2022 12:23 am If you don't have a washer tank how do you wash your windows?
You use the high-intensity washer fluid tank.

ChrisZ wrote: Mon Apr 04, 2022 12:23 am Fair enough, I put a parallel flow one in the 944S (which has an even smaller condenser) and it works very well on R134 and PAG-100 DEC oil.
Let me be clear: I have no doubt the a modern condenser would be a good thing for a 928. What I am skeptical of is if the end result is sufficiently better than a healthy 928 A/C system to be worth the effort and expense. There isn't a lot of room in the space available. And if the existing system's components aren't performing correctly then a new condenser is "fixing" the wrong thing.

It is also highly-likely that constraints I have (due to having clients) on fit, finish, and future serviceability are vastly different.

ChrisZ wrote: Mon Apr 04, 2022 12:23 am The 928S hasn't had the AC fiddled with in 3 years or so now and seems to work well.... enough but I'm always looking for improvement.
Below is a picture I took of a healthy r134a AC system in a 928 (before the freeze switch opened.) As I wrote above, if your center vent temps are not below 32 at 2000 to 2500 rpm then your existing A/C system isn't performing as well as it could be and any advantage due to a better condenser might not materialize.

All that written, it is not my intention to discourage. If it's something you want to do, and your system is healthy then go ahead.


Image
User avatar
By worf
#143461
Hey_Allen wrote: Mon Apr 04, 2022 9:51 am For what is worth, a parallel flow condenser is the only major physical change suggested when updating a MB w126 car from r12 to r134a.
You can put two 928 motors in that engine bay. Lot's of room for all kinds of solutions. And the w126 cars were made in volume sufficient for after-market development of drop-in upgrades to be economically viable.
Hey_Allen wrote: Mon Apr 04, 2022 9:51 am That said, the w126 cars had rather poor AC performance even on r12. Reportedly their systems were a bit undersized by design, at least compared to modern air conditioning designs.
Germany cars had weak A/C (on average) until the late 90s (more-or-less) as compared to US-designed cars. A/C just isn't as big "a thing" in Europe as it is in hotter parts of the world.
Formula 1 2020 And Beyond

And... both Haas cars in the points.

Bring A Trailer finds

Wow. That's off to a flying start... :rockon:

New 24 pounders are the way to go, but be prepared[…]

I lost my cool with GB and got a PM and my post […]