W124 cooling questions *yes I've used the search button ;-)
 

Hi,

I know that the W124 runs hot. I know that my car runs between around the 80 hash mark and once in awhile during the summer it might edge to the 100 hash mark...but thats only if the car isn't moving. Once the car moves it the needle quickly goes back to the 80 hash mark.

During the winter it always just below the 80 hash mark.

Recently I've noticed some things. With the AC on it more @ the 100 hash mark and during stop and go or when the car is stopped the temp is more between the 100 and 120 hash mark. Open the hood and both fans are spinning away. The needle rises too quickly from the norm but stays between the 100 and 120.

Today the weather was like 35 degrees the whole day..but the needle was at 100 during my commute to work (20miles all highway) and when I put it in park it shoots up to between 100 and 120....but more towards the 120 side.

I called my mech and he said I maybe leaking coolant and to check the coolant level once the engine has cooled down. Well the coolant level is at the correct level and I have not seen any fluid leak on my driveway....I let the car idle for 30mins.

Anyone have any ideas or insight? I'm thinking everything is fine and that somehow the thermostat might be faulty...thats just an educated guess after going through all the post regarding "temp" and "cooling" with the w124.

Last fall I had the dreaded head gasket taken care of and flushed the entire coolant. Before I had noticed that my car never ever ran above 80 even during the summer with full AC on. After the repair....during the winter the car would normally run at around 80 during the entire winter and now runs close to 100 when the temp is warm (above 60).

Thanks once again for any help....sorry about this long winded post. Thought I'd give all the details I could think of.

-Reny

Check in between the A/C condensor and radiator for blockage by dirt, leaves, etc, junk can get trapped in there and reduce cooling efficeincy.
Make sure the fan blade in mounted the correct way on the clutch- seen 'em backwards, I think bodyshops are known for getting them backwards.
After that I guess I'd try having the radiator tested at a radiator shop, they have a way on testing for internal blockages (plugged core).
Gilly

I believe someone in the past had similar issues, and cured it by replacing the coolant overflow reservoir cap. Cheap place to start, anyway.

Another thread at http://www.peachparts.com/shopforum/tech-help/19937-overheating-am-i-missing-something.html?perpage=15 found the problem to be an intermittent fault in fuse D in the fuse box, for what it is worth. Good luck.

Damn the fuse is fine....I was so hoping the fuse went bad or something.

The fans work fine...i think it has to do with the actual cooling part.

Now looks like I'll have to investigate a bit further. Blocked radiator....bad thermostat....?

Today the ambient temp was like 37, the temp remained @ 100 pretty much all the time.

When I got off the highway and drove to my work parking lot (1 mile), the temp shot up to the usual 115 and remained there until I shut the car off.

**One new item I noticed...there are two connections on top of the whole thermostat housing...the one closest to the front was a bit moist. The one next to it was dry.

I would second Gilly's recommendations and check the radiator for blockage. When the car is fully warm, touch each side of the radiator and check for hot and cold sides. If you feel a cold side then one of the radiator passages is blocked and not cooling at full efficiency.

Good luck

~Paul

____________________
'91 300E, 210k miles

In addition to the excellent suggestions from others, I would suggest checking the thermostat since they eventually fail. They can fail several ways including not opening enough which will lead to the engine running hot (they can also open too much and the engine will run cold, get stuck either open and the engine takes longer to heat up or closed and the engine will really overheat).

Good Luck!
Tom

Thank you all for the quick responses

I guess during lunch or when I get home I will try and feel the sides of the radiator and hope for the best.

Also will check into the thermostat.

If my radiator is indeep plugged....do I need to replace it or is there a way to clean it?

-Reny

Reny,
 

The thermostat is cheap and easy to replace. Make sure you get a new seal.
As far as the radiator, if it is plugged and it is the original, I would replace it with a new one or, at least, a remanufactured with warranty. You will save money at the end.
Good luck with whatever YOU decide!:cool:

when the aux fans go on at high speed it should cool that sucker down real fast. that radiator cap is one place to start, also trapped air can cause problems. the bleeder valve is on top of the thermostat housing - could it be leaking from there if you saw some moisture on one of the terminals? please post whatever you find. i have similar but milder symptoms after i had my head gasket done. i am keeping temps under control (under 100) with the resistor mod, but i have a sneaking suspicion that something isn't exactly right and summer is coming up so i want to be ready.

I replaced the line from the expansion tank to the overflow (in the right front wheel well) 2 weeks ago. It had been disconnected since we got the car, and I assumed it was only to catch the spills if we overheated. I was surprised to notice that I went from a normal operating temp of just over 90c to just over 80c with no other changes and it stayed there through our hot spell last week. Another example that these cars are made up of whole systems.

K...went to lunch...drove the car around (all city speeds) for like 10mins....temp went up to 100...so i headed back to the office and have a look/feel.

Felt the radiator:

- On the right side where there is hose that goes right to the radiator...well that side is kind of warm.

-On the left side...its cold...very cold.

After my commute back home....I'll check the sides and bottm.

Damn!

If I really need to change the entire radiator then I'm also gonna change the thermostat and its housing...they were cheap in terms of the parts price...also the coolant res' tank and cap. My tank is a little crudy looking from the whole head gasket problem.

I was disappointed but I guess I'm glad I can deal with this problem vs being stranded somewhere.

-Ren

Ren:

Don't do this if you feel it is too dangerous but I had the same exact problem and "unclogged" my radiator by happenstance. I opened up the radiator cap while engine was hot (to first detent for a moment, then all the way off when some pressure released -- use large towel if you do to not get burned) and the backflow of pressure/water had released a small blue strip of rubber that was the culprit.

Is this your original radiator? A radiator shop can unclog it effectively for around $35, unless it is really bad inside there. They symptoms you described, however, suggest that something got lodged in there just recently. (not a slow buildup of scale or grease), so I'd try the fix first before dishing out $220 for a new one.

Good luck with whatever you decide...

~Paul

__________________
'91 300E, 210K miles

Paul,

Ur giving me hope!!!

Hopefully this is the case....I think down the line I'll change the other parts....maybe end of summer.

Yes my radiator is the orginal one.

-Ren

k dumb question...where is the radiator cap?

I would think it would be top but I didn't notice any

-Ren

PS I have the Behr version

It is on the overflow tank on the passenger (exhaust manifold)side of the engine.