1989 Mercedes 300E problems

I have 3 problems with my car.

I drive a 1989 Mercedes 300E with 710,000km (all original).

Problem 1.

When driving the car I turn the A/C on and it works fine. After about 10 min of driving the heat will kick in. I pull over and turn the car off for about 5 - 10min. I turn the car back on and the cold air comes back. This problem does not happen all the time. I changed the push botton control panel to see if this was the problem but there was no change. (The replacement part was from a wrecking yard).

Problem 2.

I need to change my alternator. This does not look hard to do. The question I have is How do I loosen the tention on the belt to remove the alternator. I see the hollow 13mm bolt but in what direction do I turn it to loosen the belt and how many turns?

Problem 3.

My starter also needs to be replaced. Is this a hard job to do? What is involved in replacing it?

Any help would be great

Thanks

Fab

[bigblue1]

710,000kms!

Amazing. Your complaints sound incredibly minor.

How may kms have been done in your ownership of the vehicle?

Do you have information on what rebuilds/ overhauls have been done.

89 300CE
155k kms (not even worn in!)

[Rob Pruijt]

1- For testing the AC you will need special tools, it is probably beste to go to a AC worshop. They have the testing equipment. Last year I had an faulty pressure switch, it took them 10 mintutes to find it.

2- If you want to ajust the tension of the belt you first have to loosen the big bold in the center of the (round)rubber tensioner. Just loosen it otherwise the tensioner may drop out of the adapter plate. I'm not sure witch way to turn the hollow nut, but if the treaded rod goes down the tension will increase.
On my 126 it is possible to quick release the tension by removing the lower alternator bold and swivel the alternator up.

3- Starters are generally easy to remove. Don't forget to disconnect the battery first!. It will be easyer it you can acces it from below. Don't drop it on your head, these things are heavy.

1. Cut a piece of paper 1 CM square and hold it up to the little grille near the rearview mirror with the ignition on. It should stay in place. If it does not check the sample blower motor. This is in different locations on different years of the 124 cars. Mine is to the right of and under the glove box.

2. The bolt and hollow nut that Rob talks about are on the other side of the engine from the alternator. The big bolt goes in from front to rear and the hollow nut is almost vertical slanting down toward the engine.

Before going to this trouble, however if the problem is that the alternator is not charging, simply remove the two screws on the back of the alternator and remove the voltage regulator. This has the brushes. Check to see if the brushes are worn out. If so you can buy a new assembly for about $14 by clicking on fastlane at the top of this webpage.

3. I have never had to replace a 124 starter, but I expect it to be obvious how to do so.

Good luck,

The only major things done to my mercedes were at 680,000km rebuilt trany, the original exhaust was changed in February 05, and the head gasket was replaced in november 04.

Otherwise the car is in excellent shape except for the alternator, starter and th A/C problems.

Thanks for all you feedback. I will try all your suggestions this weekend and I will let everyone know what happens.

Thanks

Maybe others are surprised at 710,000 km but not me. It's all in how the car is driven and maintained. Here is a man who very obviously knows to keep the oil changed.

I have a neighbor with an early nineties Chevy pickup with 420,000 miles with the original engine, never been apart. If a Chevy pickup can do it, why should it be a surprise that a 300E can do it?

Have a great day,

[lee polowczuk]

I am extremely interested in knowing what kind of oil is used in that engine and how often it is changed. Quite amazing...isn't that about 400k miles?

Ditto on the voltage brushes...

I have found that many high mileage cars don't get ridiculously frequent oil changes. The reason is that for them to go to high mileage, they are probably driven for long runs on the highway. Under these conditions, extremely frequent changes are not necessary. It is town driving with lots of short hops that deplete the oil additives quickly. My 523,000 mile 240D got oil changes every 3333 miles with Chevron Delo 400. My 280,000 mile 300E gets the same.

Most any premium motor oil is capable of running the engine to this mileage as long as the oil change frequency is adequate.

I too would like to know the oil and OCI.

Have a great day,

[lee polowczuk]

Why Chevron Delo? I have been using any oil that is on sale that has an API "M" rating. I use 20w50 in the summer, 10w-40 in the winter. I change every 3k miles religiously. I think the 300ce is about due for new valve stem seals.

Originally Posted by LarryBible

I have found that many high mileage cars don't get ridiculously frequent oil changes. The reason is that for them to go to high mileage, they are probably driven for long runs on the highway. Under these conditions, extremely frequent changes are not necessary. It is town driving with lots of short hops that deplete the oil additives quickly. My 523,000 mile 240D got oil changes every 3333 miles with Chevron Delo 400. My 280,000 mile 300E gets the same.

Most any premium motor oil is capable of running the engine to this mileage as long as the oil change frequency is adequate.

I too would like to know the oil and OCI.

Have a great day,

[madbch300e]

Originally Posted by fab

I have 3 problems with my car.

I drive a 1989 Mercedes 300E with 710,000km (all original).

Problem 1.

When driving the car I turn the A/C on and it works fine. After about 10 min of driving the heat will kick in. I pull over and turn the car off for about 5 - 10min. I turn the car back on and the cold air comes back. This problem does not happen all the time. I changed the push botton control panel to see if this was the problem but there was no change. (The replacement part was from a wrecking yard).



Fab

Somone above gave advice to have it checked out completely, that is very important, since you said that "the Heat kicks in", you could be having a vacuum problem that is allowing the the heater core to kick in. Also, a bad diaphram in the changeover valve could also let hot coolant into the heater system.

As I said, most any premium oil IF CHANGED OFTEN ENOUGH will have good long term results.

I started using Delo in my diesels about 15 years or so ago. The universal grade oils such as this have much more detergent type additives to deal with the soot present in diesel engines. The oil also, however, has the highest gas engine rating available so I started using it in my gas engines as well. It keeps gas engines squeeky clean inside.

There is a common oil test that is done and the score is called Total Base Number (TBN) Delo has a very high TBN.

In my climate, 15W40 works well year round. In your climate using a lighter oil in the Winter might be warranted.

madbach300e,

The 124 car does not have a vacuum controlled heater valve. It is totally electric receiving its signal from the CCU. A vacuum problem can, however, cause the fresh air door to remain open. This will result in elevated vent temp but not HOT air out the vent.

Have a great day,

Have a great day,

I change my oil every month no matter how much I drive my car. I only use Castrol 10W 30 oil and I only use stock oil filters. Tune-ups get done every 6 months (plugs, air filter). Fuel filters once a year, trany flush once a year, every month the car gets a 101 point inspection by me just to make sure the car is running great.

[haasman]

In terms of longevity, I am not surprised either. But I am surprised by the weight of oil FAB uses, but then again he is changing it monthly which seems a bit excessive, depending of course on how many miles.


The Need for an Engine Hours Meter

The other day I was stuck in commuter traffic and I was thinking about how some engines really have many more "running hours" than their odometers would reveal. For an example, take two identical cars both with say 100,000 miles. One is driven in an urban, stop-and-go, commuter setting. The other is primarily driven in the country with rare and infrequent long periods of idling.

The "urban" car's engine will have been running many, many more hours than the "country" engine. The most dramatic example might be a police car engine or a cab.

It would be great to not only judge a prospective used car purchase by its condition, mileage etc, but also hours of engine running.

Haasman

Since fab chooses not to give his location, 10W30 may be fine. If he's in the Panama canal zone then it is a bit light, but if he's in a cooler climate then it will work fine.

Since he is changing it often, which is no surprise to me, even light multi-grade will work in warmer climates. The problem with the multigrades is that the molecules that change velocity wear out. They are coiled up when the oil is cold and uncoil when they get hot to stiffen the oil. These things wear out if they coil and uncoil too many times. Changing this oil often allows the oil to continue functioning as a 30W oil when necessary

Have a great day,

Sorry guys I live in Toronto Canada.