Parts Catalog Accessories Catalog How To Articles Tech Forums
Call Pelican Parts at 888-280-7799
Shopping Cart Cart | Project List | Order Status | Help



Go Back   PeachParts Mercedes-Benz Forum > Mercedes-Benz Tech Information and Support > Diesel Discussion

Reply
 
LinkBack Thread Tools Display Modes
  #1  
Old 06-26-2009, 02:02 PM
Needs More Boost
 
Join Date: Jun 2008
Location: Washington DC
Posts: 39
325-350 psi at 2500-3000 RPMS on the A/C high pressure line? What could cause this?

The car is a 1987 TD

The Mercedes shop - a very very well respected indy shop here in Northern Va - has had my car for over a week now. I brought it in because the A/C was blowing hot once again. Well the clutch on the compressor was fried. Mercedes warrantied the compressor, they put it on, and filled with R12.

Now this is the 3rd compressor I'm on so they wanted to keep the car and drive it for a while to see why they keep going bad. Today i spoke to them and apparently at idle the pressure on the hide side is fine, right where it is supposed to be. But once the car gets going and the tach hits 2500 RPMs the pressure reads at 325 psi and hits 350 psi at 3000 RPMs.

They seem stuck at this point on how to get the pressure down. I trust these guys completely - they have done great work on the car and are always honest with everything. Just curious if any of you guys have ever experienced this and if so what your solution was (if any). Thanks.

__________________
87 300 Touring Diesel - 197K
Bosch Euro Corners

Reply With Quote
  #2  
Old 06-26-2009, 03:09 PM
Registered User
 
Join Date: Dec 2003
Location: Festus MO
Posts: 762
Expansion valve.

My money's on a clogged expansion valve. The smallest bit of debris can clog the valve, then the refrigerant has no place to go.

SteveM.
__________________
'93 190E/D 2.5 Turbodiesel 5-speed (daily driver)
'87 190D 2.5 Turbo rustbucket - parts car
'84 Dodge Rampage diesel - Land Speed Record Holder
'13 Ram 2500 Diesel
'05 Toyota 4Runner
Reply With Quote
  #3  
Old 06-26-2009, 03:22 PM
dannym's Avatar
I'm not here
 
Join Date: Oct 2004
Location: Deltona, Florida
Posts: 2,360
That could be it. Did your indy tell you the low side pressure at 2500 rpm??

Usually high pressure on the high side is air in the system. But it could be the TX valve or even the compressor.

I'll place my bet on air in the condenser.

Danny
__________________
1984 300SD Turbo Diesel 150,000 miles

OBK member #23

(\__/)
(='.'=) This is Bunny. Copy and paste bunny into your
(")_(") signature to help him gain world domination
Reply With Quote
  #4  
Old 06-26-2009, 03:36 PM
Needs More Boost
 
Join Date: Jun 2008
Location: Washington DC
Posts: 39
The mechanic did not give me the low side pressure at 2500 RPMs. But both of those things sound like possibilities. I know they evacuated the system obviosuly when they replaced the compressor and put the r12 in - you would think that would have removed any debris. But air in the condenser could be it.

I am hesitant to call and suggest a course of action - they typically hate that... what do you guys think?
__________________
87 300 Touring Diesel - 197K
Bosch Euro Corners

Reply With Quote
  #5  
Old 06-26-2009, 03:42 PM
Registered User
 
Join Date: Jun 2000
Location: Plano, TX
Posts: 2,574
Depending on temperature and humidity it doesn't sound that far out of spec. I don't have the 124 service manual handy, but it runs higher than you would expect on the high side.

If the expansion valve was clogged you would get reduced cooling due to the restricted refrigerant flow. If it cools OK, doubt you have a problem there.

No such thing as air in the condenser. Any air in the system would circulate, along with the refrigerant. Definately not a good thing having air in the system, but doubt this is an issue.
Reply With Quote
  #6  
Old 06-26-2009, 04:58 PM
Registered User
 
Join Date: Mar 2008
Location: South Carolina
Posts: 245
Sounds like the system is overcharged. What is the low side pressure?
Reply With Quote
  #7  
Old 06-26-2009, 05:00 PM
Needs More Boost
 
Join Date: Jun 2008
Location: Washington DC
Posts: 39
Quote:
Originally Posted by jcyuhn View Post
Depending on temperature and humidity it doesn't sound that far out of spec. I don't have the 124 service manual handy, but it runs higher than you would expect on the high side.

If the expansion valve was clogged you would get reduced cooling due to the restricted refrigerant flow. If it cools OK, doubt you have a problem there.

No such thing as air in the condenser. Any air in the system would circulate, along with the refrigerant. Definately not a good thing having air in the system, but doubt this is an issue.
Mechanic believes it is about 50 to 60 PSI too high. pressure should high 200s so I'm told.

__________________
87 300 Touring Diesel - 197K
Bosch Euro Corners

Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On
Trackbacks are On
Pingbacks are On
Refbacks are On




All times are GMT -4. The time now is 07:50 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2024 Pelican Parts, LLC - Posts may be archived for display on the Peach Parts or Pelican Parts Website -    DMCA Registered Agent Contact Page