83 TD. So after a long trip, it seems the fan clutch has given out. Anytime I stop, the temperature goes up.

After one hot episode of bumper-to-bumper traffic (managed by the heater, haha), the oil pressure decides to go crazy. I am talking about the needle bouncing madly enough to make a buzzing noise. It settles down to a twitch when the car is cool. Anyhow, the pressure has twitched (a little) like this one or two times before (months ago?), I put it out of my mind since it wasn't continuous. Well now it is continuous.

So any advice on what to do? I was thinking about sticking some 15w50 in it or something. Oh, and a reminder on how to diagnose fan clutches would be nice, might swing by a jy and grab one.

oil pressure- check your oil pump.

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1986 300SDL, 211K,Dealership serviced its whole life
1991 190E 2.6(120k)
1983 300D(300k)
1977 300D(211k)

Hi

Before changing oil etc., you might want to verify what the oil pressure really is using another direct read guage.

"Twitching" is unusual. Perhaps some sludge has broken loose and is partialy blocking a line or relief valve - or you have a faulty guage.

Good Luck,

Joseph

It's a mechanical guage... not much to go wrong with it, is there?

check your O-rings on the oil filter canister. If they are hard they might not be sealing right. Is it fluctuating at idle or under load?

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92 300D 2.5L OM602 OBK #59

Hi

True. But with an unusual problem it pays to cover all possibilities starting with the easy ones

Its easier to rule out the guage and a partialy plugged oil line than to drop the pan and check the oil pump.

On the other hand it might be good to drop the pan and see whats there.

Joseph

The oil pressure relief valve is screwed into the bottom of the oil pump, and has been known to loosen up and even fall out. This is covered in the FSM, if you can determine that you don't have a gage problem, the relief valve could be a possiblity. The FSM says to reinstall loose valves with retaining compound--I called the dealer and they said use locktite.

The vibrating and buzzing of the oil pressure guage is a problem with the system itself. There are threads on the topic. I think there was a technical service bulletin on the problem and the fix is a small insert that goes in the line near the guage. Someone here bought the insert and posted pictures of it within the last couple of years.
The problem typically occurs after sustained driving at high speeds.

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

X2, I had a '79 SD which also saw the needle dance after it was driven hard but those o-rings hadn't been changed since Jimmy Carter was in the white house. I replaced them and all was well after that...try it first!

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Marty D.

2013 C300 4Matic
1984 BMW 733i
2013 Lincoln MKz

It would not be uncommon for a pressure reading gauge to have a cushioning/dampening fixture associated with it... .hope that is the problem..
Concerning the pressure relief falling out of the backside of the oil pump... this is true on many models but it is located elsewhere on some... and if one does have to go there be sure to put in the newest model available from MB as the replacement... there are different pressures associated with the different designs... ( I think " C " shown in the FSM is the latest ).

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1980 240d ,

chain elongation, cam marks reference:
http://www.peachparts.com/shopforum/showthread.php?threadid=10414

http://www.peachparts.com/shopforum/diesel-discussion/305365-9-degrees-chain-stretch.html

evap fin cleaning:

http://www.peachparts.com/shopforum/showthread.php?t=156207&highlight=evaporator

A/C thread

http://www.peachparts.com/shopforum/diesel-discussion/297462-c-recommendations-mb-vehicles.html