Where should the temperature be and why would the reservoir overflow?

[86560SEL]

Normally my 85' MB runs below 80*C on the highway and even sometimes in town if the traffic flow is good. Today was the warmest day we have had since I have owned the car (In the mid 60s) and I had to go a good deal of stop/go driving. I noticed that the temperature gauge had went above 80*C and was actually slightly above horizontal. When I would start back out, it would go back down to slightly above 80*C. When I got back on the highway, it dropped slightly below 80*C. Is this normal?

One thing I am concerned about is that when I made one stop ran in, then back out. The car was probably turned off for about 5 minutes. I came out and saw anti-freeze leaking out under the car. I got home and checked it and it had been leaking out of the overflow tank, as if it was overfull. I let it cool off and checked it a little while ago and now it is at the 1/2 mark. What is going on here? The car was recently driven 300 miles on the freeway with no problems.

Any advice appreciated.

[Hatterasguy]

Generaly they should run between 80C-100C depending on the conditions.

Is the cooling system building a lot of pressure? Hmm I'm a little stumped on this one. I'm used to diesels, in 603 world lots of cooling system pressure would be a cracked head or bad head gasket.

[86560SEL]

Oh- thanks. Well, it was not going past 100*C. In fact, the highest was barely above the horizontal. About 85*C?

Oh Lord- please do not mention cracked head or head gasket. That would kill it for me. There is no water (anti-freeze) in the oil, nor oil in the water (anti-freeze), so I am sure that is not it. It did not even overheat, but I was unsure as to where this should be.

I am thinking that the PO had added some to bring it up to par for the winter months and may have been overfilled?

I will just drive this car until the wheels fall off I guess.

Originally Posted by Hatterasguy

Generaly they should run between 80C-100C depending on the conditions.

Is the cooling system building a lot of pressure? Hmm I'm a little stumped on this one. I'm used to diesels, in 603 world lots of cooling system pressure would be a cracked head or bad head gasket.

[sbourg]

First thing I would check is the pressure cap. Is it sealing? If not holding pressure, your coolant will boil where it is resting in the head and block after it stops circulating. This will force coolant out past the poorly-sealing pressure cap.

Steve

[86560SEL]

I am assuming that it is, because it is not coming out of the cap, but one thing that I failed to mention is that the "overflow hose" where it comes out of the tank is busted right where it comes out. Would this cause it to overflow?

That is where it was coming out at.

[420 SE]

It shouldn't unless the break is below the pressure cap or as the previous post said the pressure cap is faulty.

If not, then there is a build up of pressure and it's overflowing as it should, albeit through a broken outlet. So what is the cause of the pressure build up?

Your temp is in the normal range - if fact some posts I have read even say up to 95 is OK. Is there a chance it was overfilled?? The temp sensor may be faulty giving you a falsely low reading.

As you said, you don't have oil/coolant mixing so that is a good sign.

Can't think what else.

[jbaj007]

With a faulty cap or gasket the coolant doesn't necessarily come out of the cap, but, rather, the interior part of the cap raises and allows excess out the overflow hose. I still like the cap as a suspect since it's the easiest and least $$ solution.

[86560SEL]

Thanks. I am thinking perhaps it was just overfilled, as it seems there is not a lot of extra room in these tanks. I am thinking that the PO may have added some coolant to get it to "par" for the winter. I want to change out the green coolant anyway and install the MB coolant or the Zerex coolant. The green coolant may be the problem anyway.

[haasman]

Also, if the coolant is green, most likely you have a clogged radiator.

NEVER use green coolant in these cars, NEVER. Use the proper coolant. It is well known that although expensive, Mercedes coolant is quite remarkable and is best for these cars.

To check the radiator for being clogged, after driving and the engine is fully warmed up, with the engine off reach in carefully through the fan area and see if regions are cool and others warm. If so clean and/or replace the radiator.

Haasman

[86560SEL]

Yeah, but that is what was in the car when I bought it 2 weeks ago.
If I change it out now, do you think it will be OK?
Also- how do I "clean" out the radiator if I have to?

[haasman]

You should try a citrus radiator flush. Follow instructions on the product.

You can also have a radiator shop try cleaning the system.

Be VERY careful with the old coolant. It is very toxic, kills pets by crystallizing their kidneys and they like it because it smells sweet. Please do yourself, your family, your friends (four footed and two), properly dispose of your old coolant. Do not flush it down the drain or into storm drains. Pay if you have to have it properly recycled.

Replace coolant with something compatible with alloy radiators, like the orange stuff.

Haasman

[86560SEL]

Thanks. Yeah we have cats around here, so I may just take it to the radiator shop to have them change it out if needed.

[sbourg]

Originally Posted by 86560SEL

I am assuming that it is, because it is not coming out of the cap, but one thing that I failed to mention is that the "overflow hose" where it comes out of the tank is busted right where it comes out. Would this cause it to overflow?

That is where it was coming out at.

If the cap is bad, it will come out the overflow tube, busted or not. Remove the cap and check the integrity of the rubber sealing gasket. Cheap enough check is to just replace the cap, though.

Steve