New MB owner, a lot of troubleshooting questions!

Hey guys, glad I FINALLY found a good msg board for us benz owners. I bought a 1980 300TD (wagon) last month with 170k miles in good condition, but there are a few irksome problems which I'm trying to get fixed. Advice is MUCH appreciated, since Im not only a new benz owner but a new car owner as well.

Firstly, the heater in the car does not work. The A/C doesn't work either but I was told it was because it just needs freon. It blows out air fine, no problems at all, but if the weather is cold outside, it blows cold air in the cabin. If its hot out, it blows warm air.

Second, the dash indicators are acting up. The engine temp gauge will start out around 220 degrees when I turn on the car, then 30 minutes later it goes down to about 150 after driving hard for a while. (According to the temp gauge) Is this normal? Also the gas gauge jumps around like mad and the lights that light up the dashboard at night won't come on unless I smack the dashboard 3 or 4 times. Could there be some loose connections or is it faulty gauges?

Next up: Cruise control. It just plain and simple doesn't work. At all. Nothing no matter which way I move the lever.

Last (for now!): The auto leveling rear suspension doesn't work. At all. I'm riding on springs right now, I was told by the previous owner I just need to replace the nitrogen reservoir in the rear, as the system will cease to work when those run out of gas. I ordered 2 of those from thebenzbin.com but they aren't here yet. Anyone else had this problem with their benz?

Thanks for all the help guys, expect to see me participate here a lot, cause even tho my car has some small issues I love it to death already!

Anthony Ryan

[engatwork]

Anthony - do a search on each of the listed subjects and you should come up with quite a bit of answers to your questions. Plan on spending some $$$ to resolve all of your issues with the leveling being the most costly - and this is with you performing your own wrenching. The easiest thing to fix will probably be the heater - especially since the fans seem to work.

Ain't it funny that on old cars the only thing wrong with the a/c system is that it just "needs freon" - LOL.

In case you don't know--those two middle vents above the heater controls blow only fresh air. Whatever the temperature of the outside air is what you will get through these. All the others are controlled by the heater/air conditioner.

I agree--there is currently an active post on the cruise control issue. Do a few searches and you'll come up with a lot of info. If not, post back here and you'll get a good start on some advice.

Its the 2 middle vents that don't blow anything in my car, the far left and right blow out air depending on the type of air outside, but I don't think its fresh air.

I'll do a search for cruise control and see what I can figure out, thanks!

One more thing: Fixing the heater is primary concern #1 right now, I can live without cruise control and I have a good idea how to fix the gauges on the dash, but I have NO idea where to begin with the heater, and since its below freezing at nights now and i have to drive a lot at night, its a requirement to be fixed asap.

[SW]

Regarding the heater, maybe check that the thermostat to see if its not stuck open. If so, the engine might not be getting up to normal temps and just circulating the cold coolant unnecessarily through the radiator. Thus, little or no heat especially if you are driving in below zero temps.

[Aaron]

Anthony,

If the leveling system isn't working, it could be due to a faulty pump. The way to tell if the spheres are bad is if the car bounces alot when going over a bump. The struts could also be bad. If the spheres are indeed at fault, you should also get a new filter and new MB hydraulic fluid ONLY! Don't use anything else!! I think about 5 litres will suffice for a complete flush. If you need help on replacing the spheres, e-mail me and I'll give you instructions. There are a few things you'll need to know.

I can also help you with the other problems. I just don't have time right now to write a long post. Gotta scoot!

Ok thanks for all the input so far guys!

SW: Where is the thermostat in the 1980 300TD? I checked around but couldnt find it, friend who owns an Audi 4000 said he couldn't help me cause diesel cars have their own system for everything.

Aaron: Car bounces like MAD when driving, small bumps or potholes bounce the entire back end! Also, the previous owner told me he has had to replace the spheres about once a year. Is this normal?

Thanks again!

Anthony Ryan

[Aaron]

Anthony,

Ok, if the car bounces like that, then the spheres are definitely worn. But they last 10-15 years or more in some cases without needing replacement! I'm willing to bet he did not install them correctly. You have to bleed them out once the new ones are on and must be very careful when disconnecting the lines from the old ones, as they are under great pressure. You have to crack the line open and then go just a little more every couple minutes until all the pressure and fluid stops releasing. When you put the new ones on, tighten everything up (start the flared line connection before mounting sphere!), and fill the system with fresh oil. Start the car up and bounce the rear up and down to bleed the spheres. You can crack the lines once again to let some air out or else just let it run for a while, keep checking the fluid level and also take it for a ride to further assist in bleeding. They will self-bleed if you just drive the car over some rough surfaces or keep bouncing on the back end.

The t-stat housing is at the front of the engine and is held together by three 10mm bolts. The upper radiator hose connects to it. Follow it from the radiator and you'll see the housing. Another note: The diesels tend to develop air pockets whent he cooling system is opened, so the thing to do after installing the new t-stat is to reconnect everything, but disconnect the upper hose from the radiator and SLOWLY fill the 50/50 mix in through there. It will take a while but will assure a much less chance of having an air pocket. Of course, when you start the car, put the heat on high and let it run till warm. I usually leave the radiator cap fastened only to the first detent to let pressure escape when bleeding.

On the cruise control: If you lift the lever and nothing happens, either the actuator or the switch is bad. If you lift the lever and speed increases but drops immediately, the amplifier is bad. They usually run around $180 for a rebuilt unit, exchange.

The erratic dash lights are most likely due to a faulty rheostat. They're about $40 and are easily installed.

Aaron: Thanks for the tips on installing the spheres! I will be sure to use them when I do it this weekend. Few questions tho about stuff I didn't understand: Quote: "the flared line connection before mounting sphere!" -- What exactly do you mean by that?

Also, when you mention to fill the system with fresh oil, do you mean entire car or just the rear leveling system? If just the rear system, where do you add oil for that area at? Sorry such a newbie at this stuff.

And as for the cruise control, nothing happens period. No fast jolt or anything. Its a dead lever.

Anthony Ryan

[psfred]

The flare fittings are the little hydraulic lines to the spheres. Bouncing like mad is the accumulators, for sure. Should last quite a while -- I just replaced the ones on the 88 last year, first replacment at 198,000 miles.

Make sure someone hasn't plugged the hose to the heater core to "fix" a bad monovalve -- the flow to the heater core is controlled by a solenoid valve, the diaphram of which can break, causing a full heat all the time problem. I've heard of "mechanics" plugging the line rather than replacing the valve (about $40). Also, the solenoid winding can go bad, and the valve won't close. Check for circulation before anything else.

There is also a water circulation pump to boost heat -- if this is bad you won't get much heat, either.

Check for a loose connector on the dash -- you have either a bad ground or cracked circuit board. Most likely loose wires.

You may have a bad temp sender, too.

Peter

This is NOT a picture of under my hood, this is a '82 300TD but its very similar, my question: Is this the correct location of the thermostat?

[psfred]

Anthony:

Yes -- three 10 mm screws, if I remember correctly. Rubber gasket, no sealer needed.

Peter

Ok cool at least I know where it is now. Its going to be a pain to get to it tho, I'll have to disconnect a bunch of hoses just to get the old one out. I'm hoping the weather here warms up this weekend so I can get all this maintenence out of the way before hard cold sets in. She only really needs the heater and those accumulators and she's almost in perfect shape. I'll post pics as soon as I can.

Btw I was reading some of the old threads, one especially "What makes our diesels endearing to us" and I'd have to say I totally agree with that thread. I could listen to my MB idle all day long.

Tony

[psfred]

Tony:

That looks like an AC hose on top -- don't disconnect it unless you want to be sprayed with freon! You should only have to remove the four screws and lift the top radiator hose/fitting off the thermostat and winkle the 'stat out from underneath. Easy on my brothers 300D, but it is a W115, and the AC hoses aren't in the way!

Drain some coolant first to avoid a bath in glycol!

Peter