[No4Mk1]

I've tried searching and can't find anything quite like what I'm experiencing, so any help is appreciated.

Bought the vehicle 2 years ago with about 60k miles, and at that time replaced the water pump. Vehicle today has right at 94k miles. Have serviced regularly and had minimal problems with it.

Prior to the last 3 weeks, my vehicle has always stayed right at 80-85 regardless of outside temp. In the last 3 weeks it first started edging up around 90, then closer to 100, then suddenly one day on the freeway jumped to 120, then dropped almost immediately back down to 90.

During this time I took it to a mechanic (not a dealer, but specializes in MB) who first did the 100k mile service on it. Didn't resolve problem, in fact, now the reserve started overflowing when it would get up around 100. Next changed thermostat. Still not resolved as of today.

I'm about at my wits end and really fed up with this mechanic who seems to know next to nothing about cooling systems (I had to suggest to him replacing the thermostat), so I'm looking for suggestions on what might be going on.

Could the water pump be bad again? Could the radiator be cloged?

Thanks in advance!!

 

[marcelc]

What made you replace the water pump in the first place?

Does the heater work normally? - that also can get clogged.

Better get the computer codes checked to see if there are indications of any problems there.

Is the engine running with normal power and smoothly?

 

[No4Mk1]

When I purchased the vehicle I had it inspected and in that inspection they determined the water pump was leaking. That was why I replaced it.

Heater does work normally. In fact, when the temp jumped last (has done that twice now) I cut the heater on immediately as I was in heavy traffic and couldn't get over quickly. This moderated the temp and I left the heater on all the way home. Believe me... it works... [:0]

The engine seems to be running with normal power and smoothly, but has had some rough starts from cold that started about the same time(i.e. when I first crank it will idle very rough, if I kill it and restart runs fine.)

Thanks marcelc!

 

[John_L]

Have you checked the Aux fan fuse? Its an known issue that they blow.

Bulletin T-B-83.30/62 involves installing an updated wiring harness and 40 amp fuse to correct this issue.

 

[No4Mk1]

Fuse is good, and I have observed fans working.

 

[Andrew2004az]

Sounds like a bad sensor or possible bad gauge. When it went to 120 did you smell anything burning or see any smoke from under the hood?

 

[cmitch]

Is there a such thing as a thermostat on these things?? It sounds like a sticking thermostat.

 

[No4Mk1]

cmitchprint - 4/15/2006 8:44 PM

Is there a such thing as a thermostat on these things?? It sounds like a sticking thermostat.

That was my first thought. Already replaced the thermostat, didn't resolve.

As for smell, etc, there is a definite smell of coolant boiling once it gets over 95 or so.

 

[Andrew2004az]

If you are getting a smell then you got something really major wrong. I suggest taking it to the dealer its to expensive of a car to keep guessing what wrong with it. The cost to replace the motor will be a lot more than the cost of a dealer visit. Even if you go and just get them to give you an estimate you can take that and go to an independent shop since the dealer will tell you what is wrong and what needs to be replaced.

 

[AC_ML]

There are two set of radiator fans. One dedicated for the engine and the other for when you use the AC.

When you said the fans are working are you referring to both sets..? That is the main radiator fan and the AC fans. If the auxiliary fans don't work when the AC is on and the outside ambient temperature is hot, then your car will tend to run hot..

Another question, what coolant type/brand are you using and what mixture of water/coolant did you used for your radiator...? Boiling point will vary depending on how much water you used in your mixture.

AC

 

[No4Mk1]

AC_ML - 4/15/2006 9:20 PM


There are two set of radiator fans. One dedicated for the engine and the other for when you use the AC.

When you said the fans are working are you referring to both sets..?

Yes.

Another question, what coolant type/brand are you using and what mixture of water/coolant did you used for your radiator...? Boiling point will vary depending on how much water you used in your mixture.

Don't know. Was (theoretically) flushed and replaced when I did the 100k service, but I'm not so sure.... Also was re-filled when the thermostat was replaced, but again, not sure what brand/mix.

I'm starting to feel like everyone who works on MB's in this area is either a crook or incompetent..... I've now spent about 2k on this vehicle in the last month and the problems are getting worse rather than better. I never had these sort of problems finding decent/honest mechanics when I owned US and Japanese cars. Guess I should have stuck with what worked.....

 

[rudedude]

#1,Just because the thermostat is new doesn't mean it's good. I would test the thermostat to make sure that is is opening and closing properly.

#2, you could have debris in front of the radiator

#3, the radiator could be plugged up

#4, you could have more serious problems like a blown head gasket.

#5, there may be air in the cooling system from being low on coolant.

#6, you could have a bad cooling system cap.

 

[marcelc]

No4Mk1 - 4/16/2006 1:03 AM
The engine seems to be running with normal power and smoothly, but has had some rough starts from cold that started about the same time(i.e. when I first crank it will idle very rough, if I kill it and restart runs fine.)

Well, it is a long shot, but I would consider timing and maybe replace the CPS (as it is fairly cheap and simple to do), your problem is intermittent which tends to make me think it is less likely to be a blockage, plus the CPS could be responsible for the poor starting.

I assume you are using the correct mixture of coolant and that it has been replaced at the correct intervals (3 or 4 years).

 

[ttaleric]

I was told one of my fans are no longer working also, but i have not had the engine over heat, and i have been driving in 90+ weather this week. Maybe I just need to pay attention more often.

 

[jmarenas]

Fuse #24 needs replacement, most likely blown, common problem. This powers the fans

 

[No4Mk1]

Thanks for all the suggestions folks. I've checked fuses and the're good, and all the fans are working anyway.

I've decided to take it on into he dealer and just pay the piper. Better that than risk having to look for a low-mileage used engine at junkyards.....

Now, anyone in the Houston metro that can reccomend a reliable/honest MB dealer? My experience with MB of Sugarland has been less than stellar to date.

 

[ttaleric]

Is your coolant levels good?

Also I found that my box fans work. No idea what the dealer was talking about. Thevin fools! [}]