Hello everyone,

I am a proud new owner of a 300d . . . my first Mercedes and planning on running on a WVO/diesel mix for my commute is 45 miles each way. Purchased it with no records from a kinda shady dude, but it was in good condition with 162K miles. Everything works except the Radio and the Heater. It's a pleasure to drive and it loves to go 75 mph. I had a couple of questions for y'all if you'd be so kind to lead me in the right direction. I did tons of searches and have read conflicting answers.

Heater: I had the monovalve and its housing replaced to no avail. I was told it was the temperature controller not grounding and needed to be replaced, but I didn't want to be had for another $300. All the buttons work, but the center vents do not blow air.

Operating Temperature: I replaced the thermostat with a new 80C unit, but my engine hovers at +/- 100C. I heard that this is normal from some people, and too hot from others. I plan on doing a whole coolant flush, but is there anything else I can do to keep the temp lower?

Blowby: I have some, but how can I gauge how bad it is? My filler hole blows steam when the cap is taken off, but the cap slowly jiggles as it's loosened and doesn't act like ol' faithful.

Gas Mileage: It gets around 21-23 MPG average. That's taking the miles driven divided by the amount of diesel to fill the tank. Is this normal? And is there any way to increase the #'s? 45 mile commute each way and could take a toll on my pocketbook. I heard diesel purge . . . but any other suggestions.

Rough Idle: Rough idle, but smooth sailing while cruising. Mechanic said that the IP dampener is the culprit, but don't know if it's related to the blowby and poor gas mileage. help . . .

I thank everyone for reading this and for offering your priceless knowlege.

Heater: What's the problem you're trying to fix? The center vents could be a bad vacuum pod or it could be the temp controller thinking it should be in heat mode and therefore no air should go to the center vents (for MBs of that vintage, that's a feature).

Operating Temperature: Seems high to me unless your commute is uphill both ways. Make sure the clutch fan engages when it should. Make sure the electric fan engages when it should. It might be worth pulling the radiator for a good cleaning. Clean the condenser core while the radiator is out. Consider Redline Water Wetter and no more than 40% coolant. Less if it will work where you are.

Blowby: With the engine running, plug the hose from the valve cover to the air cleaner. Measure the time it takes for the engine to shut itself off. Report back.

Gas Milage: Try running it on Diesel Keeping the engine in a good state of tune is the best you can do. Check fuel filter condition, valve lash, timing belt stretch, IP timing, etc.

Rough Idle: Replacing the rack damper is easy. If the exposed end of your rack damper is silver in color, consider a newer style replacement with a gold color end. Check the condition of the engine mounts and engine shocks. Don't forget the transmission mount. If you don't know the history of the car, it might be a good idea to have the injectors pop tested and balanced for peace of mind.

Sixto
95 S420
87 300SDL

is normal if you are driving 75 to 80 imho.

if the temp is always at 100 that seems high. did you test the stat with boiling water and a thermometer? actually i usually skip the thermometer and just watch it.

just a couple of additional thoughts... the above post, all is good.

__________________
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

Thanks guys for your replies. The heater problem I'm trying to solve is to get it working . . . no hot air blows out of the center vents no matter what the heater setting is. If the temp controller thinks it should be in heat mode, there's no heat, can it be the temp controller that's bad?

Thanks for your help on reducing the operating temperature. The clutch fan always spins so I think it's working. Also, I don't think the electric fan comes on at all. Is it operated by a temperature sensor? I'll pull out the radiator as you suggested and have it professionally flushed. I haven't tested the t-stat in boiling water when I got it so I'll do that when I flush out the system I'll look into cleaning the condensor core as well. I live in CA and the temperatures aren't too extreme to raise the operating temp of the car.

For the gas mileage, I calculated the MPG running on diesel. I replaced both fuel filters under the hood, had the valves adjusted, haven't looked at the timing belt (I thought it was a chain?) and I'll look at the IP timing issue. What is the average MPG on these cars. I've heard ~25-27 MPG.

For the Rough Idle issue, I'll go and do what you said. I don't know what rack damper I have, but I will replace nonetheless if it's not too expensive. Do you have a good source for cheap oem parts? I've ordered from mbsautoparts.com, but don't know if they'll have what I'm looking for. I'll also change all the mounts etc. How do I get the injectors pop tested? I heard of a great fuel injector shop in SSF, CA so I'll take my injectors to him.

Thanks again for all your time & advice!

If your only problem with the heater is that you can't get hot air from the center vents then you're SOL. The ACC system of your car is designed to not let heated air flow through the center vents. I won't talk about this anymore because it's a sore point with me. Part of the reason I got the S420 is because MB C O R R E C T E D this P R O B L E M in later cars.

The basic test of the clutch fan is like this. Get the engine over 100*C if you can then shut off the engine. Spin the clutch fan. If it spins freely, the clutch mechanism isn't working. If it advances a blade or two then very likely it's working. The exact engagement temperature of the clutch is in the archives. That would be the temperature at the clutch, not what's displayed in teh temp gauge.

The elctric fan should come on at low speed when the coolant gets to 105*C and at high speed when the AC compressor is engaged and pumping refrigerant. To be clear, 100*C under load is not a problem. 100*C while idling or relaxed cruising is.

It is a timing chain. I don't know why I said timing belt. I haven't had a car with a timing belt in over 5 years. Not that it means anything

The rack damper is a bolt with a spring loaded pin inside it. It bolts to the back of the injection pump. Look for a 10mm head bolt held by a nut that takes a 13mm wrench. The procedure to adjust the rack damper is in the archives. You might want to give adustment a try before you replace the rack damper. From what I hear the silver color ones have weak springs and don't last as long as the gold color ones.

A great source of parts is a click away through the FastLane button at the top of this page. No one will take care of you like Phil will and you'll be helping the economy that keeps this website going. BTW, FastLane calls the rack damper as governor idler adj. pin. Woah! They were under $50 a couple of years ago.

Pacific Fuel Injection in SSF is a good place. I hear good things about Coast(?) Fuel Injection in San Jose but Pacific is almost exclusively a Bosch shop.

Sixto
95 S420
87 300SDL

Thanks Sixto for your reply. Well, the heater problem is that it just doesn't work. No heat at all. I had the monovalve and housing replaced, and was told it was the temperature controller, but I wanted to verify before plopping some $ down on a new one or one from the local pick-n-pull.

The rack damper is a gold bolt and nut setup. I think it is closed all the way, and I might need a new one. No more adjustment is available for it is bottomed out. I'll check out what parts Phil has and will keep the $ in the clan. This site has helped me out sooo much with so much helpful and friendly advice.

Thanks again for all your help.

For your economy...

have the valves adjusted, have the timing chain stretch correct with a woodruff key, then time the IP. That should get you spot on, if not forgive me I've been out all night and it's after 3am here . Next, sounds lame but slow down a bit even 5-7mph will help a good deal.

Still running the stock tire height or taller? A taller tire will effect the MPG calculation.



The radio...

could be the lil fuse on the backside of it. If so, PM me I have a few extra I'll just 1st Class one to you.

__________________
I'm not a doctor, but I'll have a look.

'85 300SD 245k
'87 300SDL 251k
'90 300SEL 326k

Six others from BMW, GM, and Ford.

Liberty will not descend to a people; a people must raise themselves to liberty.[/IMG]

If you have a CA model '85, then your mileage is about right. The sticker on mine showed 21 city and 22 hwy. I had a tough time getting more than 24 mpg's with mine. Now that I run WVO in it I don't care about the mileage. If I had to buy diesel with the price that it is now, I would have dumped the car long time ago.

__________________
DJ


84 300D Turbodiesel 190K with 4 speed manual sold in 03/2012

Thanks again . . . well, the sticker explains the crap*y mileage then. I guess if the EPA says 21-22, then I can't squeeze 28 out of her. What did they do to the 85 calif. edition to lower the gas mileage? If it's some emission stuff to remove, please let me know.

About the radio situation, thanks for offering the fuse, but I'm planning on slappin' in an aftermarket stereo and installing some 6x9's on the rear dash, subwoofer in the trunk, and either tearing up the doors for some components or replacing the little 4"? speakers in the dash. Anyone out there with some stereo setups they want to show off?

As far as the heater goes, I'll try and find a temperature controller at the pick-n-pull to throw it in for pennies compared to a new one. What is the purpose of the center vents? I have seen people install gauges (I have boost and oil pressure VDO gauges on the way) in the center vents that look really clean. Anyone out there know of a A-pillar gauge pod source?

Thanks again for your advice everyone. I have been learned a lot!

about the ca model from experience but from this site i have observed that the entire intake and exhaust are different. they can be swapped with a 49 state setup as the engine internally is the same. if you can find a parts car cheaply or the parts it is doable.

tom w

__________________
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

Have you tested the ACC in defrost mode? Disconnect the signal to the AC compressor and run the ACC in defrost. You should get full heat. If you don't get full heat then there's something wrong the monovalve or the signal to the monovalve... which is really odd because the default setting of the monovalve is full open/full heat. Perhaps a frustrated person put a block upstream of the monovalve? I've been tempted to do that so the heater core doesn't heat soak when I leave the car for a few minutes, then get blasted with warm air while the AC re-establishes order.

Sixto
95 S420
87 300SDL