My 1983 240D has been running a bit hotter than I like lately. Today I had the needle go above the 100c mark, and I usually like to see it between the 80 and 100 marks. I did a cooling flush, but it didn't help really. As I noted in another post, I have the solid mount fan, so the clutch problem would not come into this. It does have air conditioning but I do not use it. I was just wondering if any of you had any ideas.

Thanks,
Nitro

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Nick
*****
2002 Sprinter 2500 140" High Roof :

Recently installed new water pump in my 240D.... the old pump was not entirely shot, but cast iron blades were eroded into nubs.

Valvoline has 2 types of coolant flush.... one 10 minute flush and the other you use for 6 or more hours. I've had good luck with the 6 hour flush.

thermostat would be one culprit to check, try taking it out and testing it

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83 240D four bagger stick diesel 276K

Thanks Maxwell, you reminded me I've been driving without a thermostat since replacing the water pump and flushing the system in July.

That's another thing you can do..... discard the thermostat entirely during Summer months.

Taking out the thermostat would be fine if the only purpose it served was keeping the engine cool.. but it is also supposed to get the engine up to operating temperature as fast as possible... since most wear happens between startup and that time....

240DieselDog,

Run without the thermostst in the summer? Show me where it says that in the MB manual and I will do it. Otherwise I will leave my themostat where it belongs, in the engine. Once the engine temp is above the opening of a properly functioning thermostat, the thermostat has little effect on the engine temperature.

For summer overheating, I would take the radiator to a radiator shop for flow testing and profesional cleaning.

Although running at temperatures above 100C may seem hot to us, its not hot to an engine. They are designed to run hot. As long as the coolant doesn't boil, an engine won't be damaged buy running hot. Look where the red mark is on the temperature gage. As long as temp stays below red mark in hot weather or up long hills, engine won't be damaged.



P E H

"discard the thermostat entirely during Summer months."

running w/o the thermostat will cause the engine run HOTTER because MB uses a bypass system and the coolant will BYPASS the radiator if the thermostat is removed.

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1985 Euro 240D 5 spd 140K
1979 240D 5 spd, 40K on engine rebuild
1994 Dodge/Cummins, 5 spd, 121K
1964 Allice Chalmers D15 tractor
2014 Kubota L3800 tractor
1964 VW bug

"Lifes too short to drive a boring car"

For me this has been Summertime SOP for years and years:

1)Remove thermostat..... 2) Flush the cooling system 2 or 3 times, finally running 95% straight water with just a little coolant to prevent rust....... 3)Install thermostat and add coolant in the Fall.

*footnote: the most effective way to flush cooling system is to remove thermostat first.

Haiges - MB manual is not gospel.... For example, they've got that idiot fan shroud that should be ripped right out of every car - No, it doesnt make the car run cooler for its being there.... yet it discourages ordinary maintenance and repair, creating huge hassle (just in case someone is stupid enough to jam their hands into fan blades)...... Also, just for grins, ask your dealership about putting a trailer hitch on the 4-spd. 240D. They will crap in their pants!! Sorry, but the MB manual is not the gospel.

Quote: "As long as the coolant doesn't boil, an engine won't be damaged buy running hot. Look where the red mark is on the temperature gage. "

This may be OK for you, but not for me.... aint never gonna get even close to overheating my engine - and i think on anyone who DOES overheat an engine as being incompetent for not watching the guage and not taking preventive/maintenance measures first.

Stevo - If your theory is correct, then logically a fully open thermostat also prevents the radiator from getting any water. If anything I'd expect the opposite to be true - whereby closed thermostat cuts off the radiator, channeling water through the engine instead. I dunno much about the radiator bypass system, maybe you can explain it.

Experience teaches me the '79 240D runs cool as cucumber at/near 175* without thermostat after effective coolant system flush. And warmup time is not outrageously lengthened either.

On my sailboat, the bypass cooling system allows the waterpump to circulate water without passing thru the engine block until the engine gets up to temperature. At that point, the thermostat opens and blocks the loop that bypasses the block, forcing the coolant to circulate thru the block.

I'd be curious to see a diagram of the operations of an MB cooling system since it is not clear to me exactly what is happening.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

Replace the 240D radiator with one from a nat. asp. 300D. I did 1.5 years ago and the temp never gets above 195. The radiator drops right in and you can still use the 240D hoses.

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Fred Johnson
1977 240D
1983 300SD

"they've got that idiot fan shroud that should be ripped right out of every car - No, it doesnt make the car run cooler for its being there.... "

Sorry , you are completely off on that one... air works like any fluid.... and follows the path of least resistance... and the path of least resistance is NOT THROUGH THE RADIATOR... which is where you need to air to go...
If that shroud is not there the air will be sucked up from under the car and blown across the engine... and if you are at a stop it will then be RE SUCKED UP and blown across it again...

I hope everyone will leave their shroud IN PLACE...

What should have happened.. was MB and all other car makers should have made the shroud in two pieces,,, and easily removable...

Wow...I have started quite the cooling war! I think I might have to try the 300D radiator route, that sounds like a viable alternative to me. It's either the rad. or the H20 pump because I replaced the thermo a few months ago.

Thanks for the advice guys

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Nick
*****
2002 Sprinter 2500 140" High Roof :

240DieselDog

Check your PMs, I sent you the diagrams from the service manual which should explain how the system works. I haven't time now to try and figure out how to post it. I have never run w/o the T stat or the fan shroud but if it works for you, what can I say. Here is something that should not work but worked for me... My "79' 240d was overheating last year and I drilled a small hole in the round flat part of the T stat that closes over the bypass line and the car ran cooler. Logic say that should not work but it did.

Steve

I don't know why you are surprised that helped.. Sube for instance has a small hole in the Tstat.. and SPECIFIES it be installed with that hole UP...

'Sube for instance " Whats that?? What I'm talking about is the part that closes over the bypass, the round part that is below the main body of the T stat.

Steve