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  #1  
Old 12-30-2007, 09:52 AM
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380 SL problems

Ok so i have a 83" 380SL that i have been having some major issues with lately. When i try to start the car in the morning i find my self having to open the hood removing the breather and missing with the flap every time to keep it on. Once warm it runs great. Here recently it has been overheating on me. I took it to a mecahanic and they are telling me that in order to do more testing on it i would have to replace the warm up regulator. The warm up regulator cost $500 + , but even then that wont fix all my prob. Does anyone know where i can purchase a cheaper warm up regulator and what to do about my overheating issues? Thanks
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  #2  
Old 12-30-2007, 11:11 AM
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Rebuilt warm-up regulators are available for less. I got a used one for my '85 from eBay and got lucky. I looked over what it takes to rebuild one and with the right test setup, spare cores, and a few custom gaskets, it is possible to rebuild this item to be as good as new. I "rebuilt" my bad one with adjustable cold pressure, but it remains to be seen how well it does on the car.
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  #3  
Old 12-30-2007, 11:57 AM
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There is a low-budget fix that you can try to revive your WUR.

Remove the large line from the top of the WUR. Use a pick to "fish" the metal mesh filter out of the opening in the WUR. Be sure to get all four layers. Use brake or carb cleaner to blast out any crud or debris in the filter. When you are sure that it's clean, carefully replace it in the WUR and reconnect the line.

If this filter is crudded up, it will keep the control pressure too high, which will make it hard to keep the car running until it warms up. In extreme conditions, where the control pressure approaches system pressure, it can prevent starting.

If this doesn't work, you should probably go for a rebuilt unit unless you can measure control pressure and know how to adjust it. Try Phil at Fastlane or germanstar.net. They are very easy to install.

When is the car overheating? At idle? Does the temp come down when you drive off? All the time? How high does the temp gauge go?

The first line of defense is usually a new thermostat, being sure to "burp" the cooling system when you refill with coolant. You will find several posts on this if you do a Search.
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'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe

Last edited by ctaylor738; 12-30-2007 at 01:14 PM.
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Old 12-30-2007, 03:24 PM
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Hmmm...I tried to pick out the filter from the top, but I don't think I can do it without damaging it. It did look fairly clean, and I gumoutted/brake fluid/chevronned the heck out of both sides.

I would have done this from the other side when I had it apart, but I was afraid to go in there. As it is, I think this would be a pretty serious fire hazard if not reassembled properly or if a gasket or two lets go.

I did the "plug tap" adjustable screw/nut for the small plug on the WUR as per Porsche experts on the Internet. Actually, there is a lot of info for Porche Bosch CIS systems that should be very applicable to MB's. I have the fuel pressure gauge kit and one of these days, I'll try my "rebuilt" out. I didn't have any incentive to try it now because the used replacement worked fairly well. However, I may still have to do CO2 adjustment, because I think the PO messed with this (a common thing to do to mask a pressure problem, apparently).
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http://juliepalooza.8m.com/sl/mercedes.htm
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  #5  
Old 12-30-2007, 04:19 PM
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Trouble is, it's a sandwich of four layers. Coarse mesh on top and bottom and two fine mesh in the middle. The crud accumulates in the fine mesh so you may not be able to see it. You can get it out intact with a pick or piece of fine wire.

The other critical piece is the o-ring in the valve. If it has lost it's ability to compress, then there's only a limited amount of control that can be applied to pressure. For a 380, it's a 1.5 x 14 N70.

Then if you hold vacuum on both sides, and have resistance through the heating element, you should be able to adjust the CP and be good to go. Carlos at JCP Motorsports recommends setting it cold CP to 1.0 bar and then try to get warm to 3.4. This works really well on mine.

There is really no gasket involved, since the fuel flow is only through the valve, and the o-ring provides the sealing.

Over-richening the mixture is a compensation for a bad WUR. The trick is too not ritchen it so much that the lambda system can't get control when it's warmed up and in closed loop.
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Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe
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  #6  
Old 01-03-2008, 09:44 PM
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Join Date: Jul 2007
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First off thank you guys for all this info.

Ctaylor the car temp does go down when i take off. I have also noticed when i run it for for about thirty min and arrive at my desination i can hear the water boiling. Shortly after that the water drains .
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