Hi All,

We picked the car up in LA on Friday afternoon, stopped at Trader Joes (please open one in Alaska!) and headed west. We arrived in Jackson Wyoming on Saturday night for a visit with some good friends and a day skiing on Sunday on the WY powder (well I snowboarded and it was pretty well packed...)

The car looks GREAT on the outside...no rust (CO origonal, then to AZ and then to Laguna Beach). The interior is good, except the drivers seat which has been abused by a 2,000 pound gorilla! I can see I'll be searching the site for seat rebuilding advice soon. The blower motor was nonfunctional but shims to the brushes and it works now (thanks for the information found here!). I changed the oil and filter to synthetic 5w30 and changed the airfilter and washer fluid. The car does 75 with ease and has minimal smoke. Starting in cool weather is difficult and I'm going to pay for a valve adjustment in Missoula. It will be the only time I pay for it from now on...

The advice needed:
--the heater works great at MAX but pushes cool air at any setting below max. What would cause this?

--the oil pressure gauge is at the max. A diesel mechanic (truck not MB) suggested that the sensor might be dead since old engines tend to have low pressure not high pressure. What do you think? The oil is 5w30 synthetic and is not overfull...

Thanks in advance!

The oil gauge should always be above 1.5bar (22.05psi) at idle and peg at 3bar+ (44psi) before 2000rpm. The TD uses a gauge driven directly by oil fed to the gauge in the instrument cluster. What kind of 5W30 oil? I hope it's CF or higher rated. If it's only S rated, you should change whenever you can.

As for the heater, do a search for "monovalve" and you should find what you need to change it.

Check the glowplugs to see if they work. That should greatly help your cool starting problems.

If you mean that oil pressure is at max when the rpms are up, that is good. The gauge should peg at anything above about 1K rpm and can drop as low as .5 bar at hot idle. If you mean the gauge pegs as soon as the key is on, before the engine has started, then yes it sounds like a bad sender.

Not sure what model/year we're talking here, but I would suspect a bad monovalve. When bad they typically produce heat when the car is stopped and blow cool when cruising at speed. Should be able to get a rebuild kit for about $30 or so.

__________________
Mike Tangas
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72

'02 CLK320 Cabriolet - wifey's mid-life crisis

2012 VW Jetta Sportwagon TDI...at least its a diesel

Non illegitemae carborundum.

Oh yea - make sure the engine is cold when you swap out the monovalve. Changing it out is an easy job.

__________________
Jim

I've had similar heating oddities in my 85300td. I'm pretty sure my problems lie in the electronic control mechanism. Try using the different buttons to see if things change. Sometimes if mine cools down on the far right heat button, I can get heat if I push one of the other buttons. Sometimes if I put it on defrost, it will solve the problem.
Have you been glowing more than once in the cold weather and waiting for 20 seconds or so after the glow light goes out?

__________________
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

The oil pressure gauge will show maximum at all times if:

1) The wiring to the sensor is broken, or disconnected from the sensor.

2) The sensor is defective.

To check for wiring problems, ground the wire to the sensor. The gauge should go to Zero. If it doesn't, then you have a wiring problem.

If the gauge does go to Zero when the wire to the sensor is grounded, then your problem is the oil pressure sensor. Change it

Phil

Is this car a 123? I thought all 123's had manual oil pressure gauges, not electric.

__________________
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

If you're still in WY, I have a few good monovalves and two good heater fan/motor assy's. Also, could re-solder the climate control if that's the problem. Could do a road trip if need be, email me.

Also, if it's a 123 model, the oil press should be pegged while driving, don't worry about it.

__________________
1984 300D Turbo - 4-speed manual conversion, mid-level resto

1983 300D - parts car

1979 300TD Auto - Parts car.

1985 300D Auto - Wrecked/Parts.


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"If you don't know where you are going, any road will get you there". Lewis Carrol

Yes, the 126 is electric.

Sorry folks, it is an 84 300d...

Thanks for the oil pressure info. The guage is at 1.5-2 at idle and pegs when above that so it sounds good. I was a little worried, but not anymore.

The car provides good heat when the temperature selection wheel is at MAX but only cool air at any temp selected below MAX. Sound like the monovalve? Or? Any chance of instant failure with this type of problem or will it continue as it is? Max heat north of Missoula is what I want I'm sure!

Thanks again.

check the foam tube behind the glove box.

__________________
The Golden Rule

1984 300SD (bought new, sold it in 1988, bought it back 13 yrs. later)