Overheating Issues.. Flushed System, Fresh Coolant, New Pump, Thermostat - Page 2 - PeachParts Mercedes-Benz Forum

oldsinner111 · #16 04-13-2009, 01:13 PM

keeping engine clean helps cool also.

sd300td · #17 04-13-2009, 01:23 PM

Quote:

Originally Posted by kerry

How fast were you driving at 4500rpm's??

+1, I'd like to know too...that'd be pretty much WOT in my wagon which'll heat things up a bit though I wouldn't go as far as saying its the cause of the overheating. Certainly couldn't help.

dieseldiehard · #18 04-13-2009, 03:01 PM

I'd place my bet on the radiator. If its over say 10 years old, just replace it. I also saw a thermostat problem that caused overheating. even a new thermostat is to be suspect. A sticking thermostat will mimic a bad cooling system.

LNGfish · #19 04-13-2009, 04:08 PM

Try 125 MPH and see if it cools off a bit. Much more air flow.

tangofox007 · #20 04-13-2009, 04:39 PM

Quote:

Originally Posted by dieseldiehard

A sticking thermostat will mimic a bad cooling system.

If the thermostat is malfunctioning, the cooling system is bad.

leathermang · #21 04-13-2009, 06:26 PM

Ok... I just got through reading the FSM instructions about flushing and refilling my car...

Given how involved they are... my money is on wrong procedure for refilling...

How about telling us in DETAIL ... leaving out no process... how you refilled your cooling system...

300SD81 · #22 04-13-2009, 07:12 PM

I just replaced my radiator cap today, and have a lower radiator hose on order, since mine was really soft. Will be draining and refilling coolant tomorrow in order to install the new hose.

The radiator is like new, no bent fins at all. I don't remember the exact process I used to refill, since it was quite a while ago.

Looks like that overheating caused my coolant to boil out as well, my coolant tank was extremely low when I checked it today, but was normal less than 3 days ago. It holds pressure, so I doubt that its leaking.

leathermang · #23 04-13-2009, 07:18 PM

Quote:

Originally Posted by 300SD81

Will be draining and refilling coolant tomorrow in order to install the new hose. .

Do you have a ' plan' for that ?

CarlG · #24 04-13-2009, 07:43 PM

Quote:

Try 125 MPH and see if it cools off a bit. Much more air flow.

Well put. I'd be willing to bet that the problem is your driving style rather than your cooling system. I'm usually not one to to back seat drive, especially from my computer desk, but seriously, slow down. You're only hurting your car if you don't.

As for your 85C at idle and 90C driving, I'd say these are perfectly normal. The factory service manual says that the operating temperature of these cars is supposed to be something like 80-90C.

Also, the factory manual says a 55/45 mix of 55% water 45% coolant, not the other way around.

JonL · #25 04-13-2009, 08:24 PM

Quote:

Originally Posted by 300SD81

I just replaced my radiator cap today, and have a lower radiator hose on order, since mine was really soft. Will be draining and refilling coolant tomorrow in order to install the new hose.

The radiator is like new, no bent fins at all. I don't remember the exact process I used to refill, since it was quite a while ago.

Looks like that overheating caused my coolant to boil out as well, my coolant tank was extremely low when I checked it today, but was normal less than 3 days ago. It holds pressure, so I doubt that its leaking.

Well, I HOPE I'm being a nervous-nelly... With a good pressure cap and 40% glycol, you'd have to get it REALLY hot to boil out the coolant. The high temperature and loss of coolant might mean head gasket (or worse). Of course, it could also be that you had a nice big slug of air in there... reference Leathermang's comments about bleeding the cooling system.

JonL · #26 04-13-2009, 08:25 PM

And I wouldn't worry about the speed (other than the safety of others on the road). People commonly drive for extended periods at 100MPH in Europe where these cars were born.

exhebetche · #27 04-13-2009, 08:37 PM

My .02 cents: check the wire going to the coolant temperature sensor, located on the injector pump side of the motor. Beige brick's temperature was never 100% perfect, then it started overheating, Oh NOOOO....!

Then, after a long process of elimination; thermostat replacement, water pump checks, coolant line checks, it all boiled down to the coolant temp sensor wire being so corroded that it pulled off from the sensor when I barely yanked it. Resoldered the connection between the wire and the sensor, and the car stopped 'overheating' and is still fine today. When the wire was disconnected the dash temp reading was maxed out.

Just another thing for you to check, if you fix/replace everything else and do everything by the book as to flushing the cooling system, and the car is still toasty.

leathermang · #28 04-13-2009, 11:20 PM

Quote:

Originally Posted by CarlG

Also, the factory manual says a 55/45 mix of 55% water 45% coolant, not the other way around.

I assume that was directed to me....

Here is the quote from the 1981-1993 MB maintenance manual.
supplement 5 , March 1993. Page 2080/3

" Corrosion protection/antifreeze....

approx 50 percent by volume of antifreeze must be added to the water. The concentration provides antifreeze protection down to approx -37C.
A higher concentration is only practical with even lower ambient temperatures.
Exceeding 55 percent by volume of corrosion protection/antifreeze agent reduces the antifreeze protection as well as the heat dissipating ability of the coolant.
55 percent by volume of corrosion protection/antifreeze agent proves (SIC) antifreeze protection down to approx -45 C.

Checking Coolant in service

...
When refilling after coolant loss ensure that the coolant contains 50 percent by volume of corrosion protection/antifreeze ( protection down to -37C).
... "

The way I read that is that 50 percent antifreeze is the lowest amount recommended.....and 55 percent antifreeze is the highest...

which I wrote as " For long term MB suggests the 50/50 or 45/55 ( water/AF ) partly due to the anticorrosion features.. "

If they changed the recommendation can you point us to the literature ?

300SD81 · #29 04-14-2009, 03:43 PM

Just changed the lower radiator hose, and filled with 50/50 mix, didn't drain the block though, so I'd guess it has about 55/45 inside now. Its still running hotter than my other car, staying around 90 at idle and 100 driving. The other one only ever went to 90 under heavy load in the summer... Maybe it is my sensor, will try getting a new one. I checked the wire, and its fine. Does anyone know what the resistance should be at certain temperature?

JonL · #30 04-14-2009, 03:47 PM

Did you correctly bleed the system? Do you have heat? I'm still curious about where your coolant went before when you found the level to be low.