Why Is Temperature So High - PeachParts Mercedes-Benz Forum

NY2LA · #1 03-20-2007, 02:30 PM

Recently I was driving on the freeway and I noticed that my temp guage went as high as 120c but not into the red... the temp. outside was not hot maybe around 78*. I replaced the themostat and flushed the radiator and added new coolant... then took it out on the freeway again with outside temp at around 60* and the needle went from 40-89 in about 4-5 mins but never went above 90...
Someone made the remark that the radiator could be losing pressure around the tank seal. It is not losing coolant. I have not had to put coolant in the resevoir in over 2 yrs.
Is it possible for a temperature rise to be caused by a radiator that is losing pressure and how do I determine if that is my problem. Could there be anyother problem I am overlooking?

rrgrassi · #2 03-20-2007, 02:42 PM

Quote:

Originally Posted by NY2LA

Recently I was driving on the freeway and I noticed that my temp guage went as high as 120c but not into the red... the temp. outside was not hot maybe around 78*. I replaced the themostat and flushed the radiator and added new coolant... then took it out on the freeway again with outside temp at around 60* and the needle went from 40-89 in about 4-5 mins but never went above 90...
Someone made the remark that the radiator could be losing pressure around the tank seal. It is not losing coolant. I have not had to put coolant in the resevoir in over 2 yrs.
Is it possible for a temperature rise to be caused by a radiator that is losing pressure and how do I determine if that is my problem. Could there be anyother problem I am overlooking?

The build up of pressure helps to keep the coolant mixture from boiling out. The cap is there to regulate pressure. It is possible that you had a stuck closed t-stat as well, and replacing it solved the problem. But at two years it is time to look at the expansion tank itself and the cap.

gsxr · #3 03-20-2007, 02:43 PM

After the work you did, the temp never went over 90°C, right? Sounds like the problem is solved. If not, it would help to know the year and model of your car...

vito · #4 03-21-2007, 08:36 PM

Quote:

Originally Posted by gsxr

After the work you did, the temp never went over 90°C, right? Sounds like the problem is solved. If not, it would help to know the year and model of your car...

So you would say 90c is normal? Mine moves around 85-95c. When I turn the heater on it will quickly drop to around 80+1-2.

anghrist · #5 03-22-2007, 01:29 AM

Quote:

Originally Posted by NY2LA

Recently I was driving on the freeway and I noticed that my temp guage went as high as 120c but not into the red... the temp. outside was not hot maybe around 78*. I replaced the themostat and flushed the radiator and added new coolant... then took it out on the freeway again with outside temp at around 60* and the needle went from 40-89 in about 4-5 mins but never went above 90...
Someone made the remark that the radiator could be losing pressure around the tank seal. It is not losing coolant. I have not had to put coolant in the resevoir in over 2 yrs.
Is it possible for a temperature rise to be caused by a radiator that is losing pressure and how do I determine if that is my problem. Could there be anyother problem I am overlooking?

That sounds like you've fixed it. Out here in the high desert, we have to sysle the A/C on/off to keep the temp below 100C when the summer heat gets up around 120F.

tobybul · #6 03-22-2007, 08:34 AM

Per my Haynes manual, the temp should top out at around 94 deg C. Looks like you are now on target. Must have been the tsat.

mespe · #7 03-22-2007, 10:09 AM

MY diesels always run around 80C. Replace the radiator cap, and you might drop another few C's

vstech · #8 03-22-2007, 10:43 AM

if it's sitting around 95C and you are not running the a/c I would flush the motor with fresh water, and drain all the coolant from the block, then do a real citric flush. AMAZING what will come out of a "super flushed" block. that acid really does get all the gunk out.
John

gsxr · #9 03-22-2007, 12:03 PM

Quote:

Originally Posted by vito

So you would say 90c is normal? Mine moves around 85-95c. When I turn the heater on it will quickly drop to around 80+1-2.

Yes - 90°C is normal. Actually anything between 80-95°C is absolutely, totally, perfectly, normal. Between 95-105°C, that's still fine if it's very warm outside and you have the AC on, or if you are climbing a long steep grade. BUT.... above 110°C, unless you're in Death valley, something isn't right.

There's no need to try to achieve 80-85°C all the time and on some cars, you never will. My 84 was usually 85-90°C, my '87 stays at 90-95°C year round, and my new 93 has been right at 90°C all winter (haven't driven it in summer yet.)

If you're not using Mercedes or Zerex G-05 antifreeze, I'd strongly recommend it. Read this link (2MB PDF file) for more info. I use one gallon of a/f, and add one bottle of Water Wetter.

tobybul · #10 03-22-2007, 12:17 PM

Quote:

Originally Posted by vstech

if it's sitting around 95C and you are not running the a/c I would flush the motor with fresh water, and drain all the coolant from the block, then do a real citric flush. AMAZING what will come out of a "super flushed" block. that acid really does get all the gunk out.
John

Where do you usually find citric acid for this purpose?

gsxr · #11 03-22-2007, 12:28 PM

Quote:

Originally Posted by tobybul

Where do you usually find citric acid for this purpose?

You can order it with the Mercedes part number, 000-989-10-25, which is a 0.5kg bottle. You need 1.0kg (2 bottles) for most engines. It's about $15/bottle wholesale. Or, I've been told you can buy it in bulk from chemical supply stores cheaper. More details are in this PDF file:

http://www.w124performance.com/docs/mb/OM60X/citric_acid_flush.pdf

Totally flush the system at least 3 times afterwards, getting the engine up to operating temp each time, and having the heater on max. This takes hours... not a fun process.

cmp · #12 03-22-2007, 12:40 PM

Mine was overheating, particularly at idle...

I replaced the thermostat, and flushed. Still happened. After replacing my belts, all is back to normal. Maybe loose belts are causing the problem?

gsxr · #13 03-22-2007, 12:52 PM

Belts could definitely be an issue on any engine with V-belts (OM61x), as you learned first-hand.

The newer OM60x engines all have serpentine belts with a spring-loaded tensioner. Overheating at idle with these is, in many cases, due to internal desposits inside the radiator (after all the 'basic' stuff has been checked - Tstat, cap, clean fins, good fan clutch, flush, etc etc).

vito · #14 03-22-2007, 01:52 PM

Quote:

Originally Posted by gsxr

Yes - 90°C is normal. Actually anything between 80-95°C is absolutely, totally, perfectly, normal. Between 95-105°C, that's still fine if it's very warm outside and you have the AC on, or if you are climbing a long steep grade. BUT.... above 110°C, unless you're in Death valley, something isn't right.

There's no need to try to achieve 80-85°C all the time and on some cars, you never will. My 84 was usually 85-90°C, my '87 stays at 90-95°C year round, and my new 93 has been right at 90°C all winter (haven't driven it in summer yet.)

If you're not using Mercedes or Zerex G-05 antifreeze, I'd strongly recommend it. Read this link (2MB PDF file) for more info. I use one gallon of a/f, and add one bottle of Water Wetter.

thanks for the info...

#15 03-22-2007, 09:13 PM

Quote:

Originally Posted by cmp

Mine was overheating, particularly at idle...

I replaced the thermostat, and flushed. Still happened. After replacing my belts, all is back to normal. Maybe loose belts are causing the problem?

Belts will do it if they are slipping. I've also replaced my fan clutch twice in the last 200K miles when it heated up in stop and go traffic.

I recently replaced my radiator (due to broken neck) and it seems to be running about 5C cooler than it did with the old radiator in summer (90F) conditions.