The Dreaded Evaporator Pressure Regulator

[Jim Van]

Ok, still waiting on my 90 LS400 to come out of the shop. 8 days counting today, I finally went into the shop and asked what the heck....not so nicely....and I was told this EPR was something they have never seen before and they did not know what to do. Now to give the history, bought the car for 1k (which was steal actually) and had Lexus do the pre-sale inspection and the only failure was the A/C did not work no other black marks on the report.

Now the guy I bought it from already purchased the compressor which was still in the box in the trunk (hence why I thought for 1k the deal was to good to be true). Now I had my guys install the compressor, expansion valve, dryer and convert to 134a. Called them on Thursday as they requested since the parts had to be ordered and was told tomorrow for sure, called on Friday and was told tomorrow for sure. Well I into the place and the guy showed me the EPR and asked for my permission to open it up and see if it is plugged up and the cause of my A/C not blowing cold. Ok, we opened it and yep it was full of the remains of the original compressor so we dismantled it all the way down and cleaned it up.

As we reassembled the EPR we notice the rubber skirt was torn about 3/4 of an inch. Well the Lexus dealer here parts department is not open on Saturday (just my luck) but I said put it in and if doesn't work I will go to AutoZone and get a new one (hahahhaha). Put it back together, installed it, charged the system, started the car and hit the A/C switch with our fingers crossed. Well low and behold the A/C blew cold my mechanic was smiling ear to ear because he finally got everything to work. That lasted all about 10 seconds and than the A/C started blowing warm; he cycled the A/C on and off with about 5 seconds in between and the A/C blew cold and had pressure on the Freon gages. Now when the A/C started blowing warm the pressure gages dropped to zero so we believe it is the EPR. Since this is a singe evaporator system what will happen if we gut the EPR and hook everything back up? Will it cause major failures or will the A/C work but I will get A/C "groan" when I shut the car off after driving with the A/C on?

If I must have a fully functioning EPR does anybody know where I can purchase one? (besides the dealer and the junk yard, ebay is part of the junk yard since I cannot find one new).

Thanks,

Jim

[wwest]

Ok, still waiting on my 90 LS400 to come out of the shop. 8 days counting today, I finally went into the shop and asked what the heck....not so nicely....and I was told this EPR was something they have never seen before and they did not know what to do. Now to give the history, bought the car for 1k (which was steal actually) and had Lexus do the pre-sale inspection and the only failure was the A/C did not work no other black marks on the report.

Now the guy I bought it from already purchased the compressor which was still in the box in the trunk (hence why I thought for 1k the deal was to good to be true). Now I had my guys install the compressor, expansion valve, dryer and convert to 134a. Called them on Thursday as they requested since the parts had to be ordered and was told tomorrow for sure, called on Friday and was told tomorrow for sure. Well I into the place and the guy showed me the EPR and asked for my permission to open it up and see if it is plugged up and the cause of my A/C not blowing cold. Ok, we opened it and yep it was full of the remains of the original compressor so we dismantled it all the way down and cleaned it up.

As we reassembled the EPR we notice the rubber skirt was torn about 3/4 of an inch. Well the Lexus dealer here parts department is not open on Saturday (just my luck) but I said put it in and if doesn't work I will go to AutoZone and get a new one (hahahhaha). Put it back together, installed it, charged the system, started the car and hit the A/C switch with our fingers crossed. Well low and behold the A/C blew cold my mechanic was smiling ear to ear because he finally got everything to work. That lasted all about 10 seconds and than the A/C started blowing warm; he cycled the A/C on and off with about 5 seconds in between and the A/C blew cold and had pressure on the Freon gages. Now when the A/C started blowing warm the pressure gages dropped to zero so we believe it is the EPR. Since this is a singe evaporator system what will happen if we gut the EPR and hook everything back up? Will it cause major failures or will the A/C work but I will get A/C "groan" when I shut the car off after driving with the A/C on?

If I must have a fully functioning EPR does anybody know where I can purchase one? (besides the dealer and the junk yard, ebay is part of the junk yard since I cannot find one new).

Thanks,

Jim

Jim,

I think, but certainly am not sure, that the EPR valve has a capillary tube going from it to the expansion valve and that tube has something to do with the expansion valve operation (opening??). But an any case given the "task" assigned to the EPR, regulate the back pressure on the evaporator's refrigerant outlet side, removing it might very well result in "slugging" (liquid refrigerant) at the compressor inlet.

On the other hand I'm not so sure that at times the EPR doesn't itself often result in compressor slugging. On my original, bought new, '92 LS, and the '92 I bought later at 150,000 miles, the compressor low side refrigerant return lines will often be coated with 1/4 to 3/8 of rhime ice after about a 150 mile drive. Also, with both of them I have had instances, periods, of zero, ZIP, cooling with substantial blower airflow while traveling up mountainous inclines. I suspect compressor slugging in both instances.

I think I would figure out a way to install a more standard expansion valve if I were removing the EPR.

On another subject. Methinks that almost all minivans, like my '94 AWD Aerostar, with independent F/R A/C systems include an EPR or some sort of equivalent. So it is a bit surprising to find a shop that has never seen one.

[Jim Van]

I agree about the minivans but they did not equate the two until I spoke to them this morning and they agreed with the rest of us, what is the use of this part on single unit A/C? Well back to my tale, grinded a BIG NOTCH in the small side of the piston put all back together and it leaked like sieve we assume through the torn rubber skirt we saw yesterday (through a factory made hole in the upper bell housing of the EPR no idea why this hole is there). Good news is it blew cold air until the mechanic turned it off because he was concerned about running out of Freon........so we assume the work around is to grind the notch into the piston in the EPR and let the expansion valve do it's job but with the tear in the rubber skirt we cannot stand behind our judgment 100%. Going to the “you pull it yard” tomorrow and if I find an EPR with good rubber skirt going to notch it and run it, what is the worst that can happen kill my compressor? From what I have seen on this forum seems like my compressor is a dead man walking anyways because of the EPR so might as see if I make it a slow walk or a full out run........

[grivlexus]

I've successfully worked around the failed EPR valve on my '92 SC400 with 215k and kickin' you know what. Lexus wanted about $674 for that valve, and even at a discount I could only locate one for $546. A junkyard unit worked for three days before it, too, disintegrated. The rubber just doesn't hold up. (Heck, half the wire connectors on my ignition have all self-destructed.)

But the solution is simple. You'll need a 2" square piece of 1/4" aluminum, quality gasket material and hi-temp silicone sealant.

Remove the failed valve flange assembly from the valve body, accessible via the four phillips screws. Machine the aluminum to about the same size as the outline where the valve went. Create a plate from the aluminum and drill the four holes necessary to mount the plate to the EPR. The red stuff is Loc-Tite on the four phillips.

Cut a gasket to the same size, and when ready, use high-temp silicone to line the area where the gasket will fit on the EPR. I suppose lining both sides wouldn't be a bad thing. Careful not to put too much on - a thin finger glaze will work. Mount the plate and gasket to the EPR, tighten the screws like you would a four-stud tire (cross-wise), and then wait a day for the silicone to cure. Cool your heels. They'll be cooled soon enough by your working AC!

The next day, put your vacuum pump on and clear the system out. If the vacuum holds for a half-hour or so, attach your refrigerant tank (I used Forane 409a). Purge your lines, and then introduce the refrigerant. Note: 409a goes in as a liquid - otherwise you can destabilize the gas mix that makes up 409. I loaded about two lbs (I measured it with a Pitney Bowes scale for accuracy).

I repaired mine over a month ago, and it's tight as a drum.

A note on the EPR: Denso (the manufacturer) has a great little 12 page booklet PDF out there that explains the function of the EPR. http://napabeltshose.com/file_display_common.cfm?thispath=napa_hc%2Fdocuments_module&file=AC_Fundamentals_2-Condensor_Functions.pdf

It's job essentially is to prevent frost on the evaporator in cooler, humid climates. I live in south FL and we pretty don't much worry about that. So I jumped it out. This past June saw days here of 96+ and I was just fine. By the way, my SC is black.

[SupraTico]

WORST advice ever.

Did this to my EPR about 2 years ago and have subsequently had 3 (count them, THREE) compressors fail.  The system has been flushed, the dryer has been changed each time, and the condenser was changed once. 

All of them have been factory units. They all begin failing in the exact same way... they start to get noisy, rattly, and then seize up and fail.  I was told by an A/C tech that this was due to slugging, which was caused by not having this "useless" valve.

On 7/7/2011 at 0:43 AM, grivlexus said:

But the solution is simple. 

 

 

[Exhaustgases]

Define "Slugging".. ????