Increasing engine temp - PeachParts Mercedes-Benz Forum

clint77002 · #1 05-05-2006, 10:40 AM

81 300D N/A
new thermostat (1 week ago)
radiator flush w/ MB Citrus (1 week ago)
MB coolant mixed 50-50

Today as I drove to work (without A/C), all seemed well, then the temp quickly went from 180F to 200F. I turned on the defroster and the temp went back to its previous level. I turned off the defroster and the temp stayed at the 180 level. What is happening here? I am concerned at the quick temp rise before I turned on the defroster and that something is stuck and not letting coolant in or something else.
Any clues?

Diesel Giant · #2 05-05-2006, 02:51 PM

Could be lots or reasons. You may have the infamous hot run syndrom. Here is some things I did as a last resort.

http://dieselgiant.com/thermostatreplacementandmodif.htm

clint77002 · #3 05-05-2006, 03:23 PM

I had considered removing the thermostat altogether. I live in Central Texas and it rarely gets very cold. My dad used to remove thermostats in his Ford pickups in West Texas (where it gets much colder). Does anyone forsee any ill effects from removing the thermostat?
Thanks,
clint

Diesel Giant · #4 05-05-2006, 03:29 PM

Dont remove the t-stat. Just modify it and you get the benefits without the lack of the t-stat.

t walgamuth · #5 05-05-2006, 05:54 PM

personally i dont recommend modifying your stat.

you may have a plugged radiator even though it has been flushed.

also could be water pump. these often leak when failing but not always. sometimes they spin the impeller. or the blades get eaten away sometimes too.

tom w

300SDog · #6 05-05-2006, 06:11 PM

Yeah a wornout water pump can be insidious with blades corroded down to nubs even if its not leaking. By modifying the T-stat folks are talking about drilling out the collar with small holes. Or there's usually an original T-stat hole that should be pointing up at its highest point. This prevents air chamber from forming at one side or another of the T-stat.

And if it was me, I'd flush it again for good measure using valvoline 6 hr radiator flush. Meanwhile have you thought about a manual toggle switch for the auxiliary electric fan to bypass the automatic fan control?

tangofox007 · #7 05-05-2006, 06:22 PM

Quote:

Originally Posted by clint77002

I had considered removing the thermostat altogether. I live in Central Texas and it rarely gets very cold. My dad used to remove thermostats in his Ford pickups in West Texas (where it gets much colder). Does anyone forsee any ill effects from removing the thermostat?
Thanks,
clint

On many engines, removing the thermostat results in essentially the same condition as an open thermostat. But it does not work that way on engines with a bypass type thermostat.

Diesel Giant · #8 05-05-2006, 10:04 PM

The t-stat is a last resort mod as I said earlier. I had a car that I did everything to and it just would not run cool. Did the mod and would run a solid 82 celcius in the hottest weather and never did overheat again.

In the winter I just slid a piece of cardboard between the radiator and condensor and it warmed up fast and ran a perfect 82 also.

Who knows why it works so good, but it does.

t walgamuth · #9 05-05-2006, 10:40 PM

i just cant imagine that the mb engineers would design a thermostat housing that restricted the flow at all.

and if that is true, then drilling holes in the stat body won't help.

just my opinion. i think it is pretty hard to think and get ahead of the factory engineers.

well maybe on the frankenstein ac bracket on the 115 and early 123 cars!

tom w

300SDog · #10 05-06-2006, 12:53 AM

Tom, I think its close tolerances and tight clearances where MB screws up alot. When turning on the heat drops coolant temp by 5 degrees, you can bet there's not alot of play in a cooling system that finely tuned.

After hitting a deer with my 240D couple of years ago, installing a junkyard Mitsubishi radiator made all the difference in the world - vastly improved engine cooling in Summer months and never ran cold in Winter either. And the Mitsubishi rad was a perfect fit that even left room for the oil cooler.

t walgamuth · #11 05-06-2006, 06:17 AM

maybe.

but a little here a little there, and it all adds up to something. personally, if everything is working correctly, i havent ever had a problem.

lets see, am i remembering correctly that you dont run your radiator shroud? mr dieseldog? this an element of the cooling system, and directs the air and will affect cooling for sure especially at idle. just one little element in a big picture.

course, i am further rnorth but we have our days here that the summer can be a lot like new orleans 100 degrees with same humidity about. but we just have them occasionally and after three or four days i usually gives us some relief.

tom w

signalredcoupe · #12 05-06-2006, 09:18 AM

I've never had a problem with the two 123's I came across except for one thing. When I first bought my coupe, while driving it down from up North, the temp. was fine until I hit Northern Florida. Then it started to climb to about 100c & remained there till I got it home. What I found was the radiator was plugged in between the fins with fine grit like sand. A garden hose & compressed air fixed it. These cars are 20-30 years old. Plenty of time for stuff too small to notice to restrict airflow. my 2c Enjoy Paul.

300SDog · #13 05-06-2006, 02:50 PM

Quote:

Originally Posted by t walgamuth

...lets see, am i remembering correctly that you dont run your radiator shroud? mr dieseldog?

Tom, all sorts of unwanted fiddly bits were boned from my '79 240D...... vacuum locks, cruise control and the entire A/C system. I've got it down to just one vacuum line (engine shut-off) leading to the engine. And just a couple of electrical lines too - the temp guage and glow plug wire.

Meanwhile Autozone carries a steeper pitch universal aluminum fan blade that replaces the original 240D shallow pitch plastic fan. And the Mitsubishi radiator was greatest improvement of all. Who needs a fan shroud with the cooling system souped-up with superior Non-MB components?

Am amazed that anybody tolerates the fan shroud constantly getting in the way. I've got no patience for over-engineered junk that MB throws into their cars. They should probly fire half their engineering staff and recruit craftsmen instead. Much of the crap they put into these cars is truly laughable.

MB builds the finest engines, drive-trains, suspensions and coach - extremely well ballanced. But then they go overboard with junk tech accessories. Look at the manual sunroof, genuine work of art replaced by screwball electrical cable operated unit that's a howling joke.

Panzermann · #14 05-06-2006, 03:57 PM

the new stat could be defective. Happened to me once. Check it or replace it. Drilling holes in the thermostat to allow some baseline coolant flow is one approach, or you can use a thermostat from the 1970's 450 models, which opens at 76 C instead of 80 C (the stock). I installed one due to some overheating in summer stop/go traffic here in tucson with the a/c on and it made a real difference.

t walgamuth · #15 05-06-2006, 04:25 PM

Quote:

Originally Posted by 240DieselDog

Tom, all sorts of unwanted fiddly bits were boned from my '79 240D...... vacuum locks, cruise control and the entire A/C system. I've got it down to just one vacuum line (engine shut-off) leading to the engine. And just a couple of electrical lines too - the temp guage and glow plug wire.

Meanwhile Autozone carries a steeper pitch universal aluminum fan blade that replaces the original 240D shallow pitch plastic fan. And the Mitsubishi radiator was greatest improvement of all. Who needs a fan shroud with the cooling system souped-up with superior Non-MB components?

Am amazed that anybody tolerates the fan shroud constantly getting in the way. I've got no patience for over-engineered junk that MB throws into their cars. They should probly fire half their engineering staff and recruit craftsmen instead. Much of the crap they put into these cars is truly laughable.

MB builds the finest engines, drive-trains, suspensions and coach - extremely well ballanced. But then they go overboard with junk tech accessories. Look at the manual sunroof, genuine work of art replaced by screwball electrical cable operated unit that's a howling joke.

i agree with the overengineered stuff, like automatic ac controls. but i wouldnt put the fan shroud in that catagory.

tom w