I recently completed a 2,000 mile cross country trip in my '82 300d from ohio to utah running on biodiesel and straight veggie oil while filtering WVO on the way (cross country for free, that's a good feeling). When I got into Kansas I noticed the benz was running a little hot...in between 100 C and 120 C. When I got to the mountains of Colorado it overheated a couple of times so I changed the thermostat in Brekenridge.

I was pretty loaded down with veggie oil and a new thule roof rack, but it's still running hot. When I run on cruise at about 75 mph the needle stays around 110, then it will just jump up to 120. Then i'll back off to 60 mph for a while, let it cool off to 100 or less, then bump the speed back up or i'll just pull over to let it cool. Also i hooked up the aux. fan straight to the fuse box and this didn't help at all.

Should I change the radiator or just have it flushed?

How much would I expect it to pay for a new radiator (i'm going to install it myself) and where is the best place to look for one?

Thanks.

i got a used one for 50 bucks off ebay...

I am brave but your doing something i would not do...
I never let my car go above 90 I would totally remove
the thermostat.... and I would turn the car heater on when it
hit 95....

I would jumper the ac fan so it blows all the time...

red line sells a product that they claim will bring the temp down 8 degs.
its in a little bottle and the liquid is red.

sometimes the plastic neck of the radiator breaks and we dont know that it
has popped and you could be loosing preasure and coolant there causing it to over heat... the newer radiators have a metal insert to keep it from happening.. and if you still have the older radiator and your letting it get to 110 then your really risking having that neck pop... It popped on mine when it was at 100.... sometimes it can break and you not be able to tell it broken.
that is the neck where the top radiator hose connects...

From your post it doesnt seem like you checked the fluid level? did you check to make sure there is no coolent leaks that may be the cause of the over heating?

__________________
Current:
05 E320 CDI
07 GL320 CDI
08 Sprinter
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2004 E55 AMG
2002 C32 AMG (#2)
1995 E300
1978 300D
1987 300D
2002 C32 AMG(blown motor :[
1981 300SD
1983 300SD
1987 300SDL
2002 Jetta TDI
1996 S420
1995 S500
1993 190E 2.6
1992 190E 2.3
1985 190E 2.3 5-Speed

Yes the coolant level is maintaining a constant level and it barely moves. When it's running hot it seems like the coolant reservoir starts to get filled up with more coolant. Then when it cools down the coolant level in the reservoir gets lower, if that makes any sense.

that makes good sense....

remove the thermostat and see if it still runs hot...
also i have heard of fellows drilling 6 holes in the outside of the
thermostats so that a little water will flow...

diesel giant specializes in the holes

I have heard that removing the thermostat is not a good idea...will this make it run cooler? It is 100 degrees here in Utah now.

You are correct, you do not want to run a 617 without a thermostat. The thermostat is required to ensure flow through the radiator.

You can try "water wetter" and see if it helps, I tried it once and didn't notice much of a difference.

1. You need your thermostat for MPG. My engine was running cold (70C) and my economy stunk. I change the thermostat and gained about 2.3mpg in fuel economy.
2. Try to flush the radiator.
3. Be sure there is air passage in the radiator. Years ago I flushed a radiator thinking my problems were over however, the car would still over heat due to all sorts of junk that blows into the radiator fins. I recommend removing the radiator, examine it, and do what is necessary. Long term it will be well worth the time.


Note: A new radiator or recording your radiator may seem pretty expensive, however, it has a big impact on the health of you engine that cost even more. Are you willing to nurse a bad radiator at the expense of you engine.

i disagree i own a 617 and i remove the thermostat back before i
replaced the radiator...

dieselgiant has a section on drilling holes in the thermostat....
go and read that....

You have a new thermostat, so now I would remove the radiator and blow out all the fins and flush it.
Then reinstall but just run straight water for now and see if it still gets to warm.

read this and you will find your answer

http://www.dieselgiant.com/thermostatreplacementandmodif.htm

Note that DieselGiant's write-up includes the following statement:

"My recommendation on t-stat modification is that it is a LAST ditch approach. Replace or repair all the items I listed a few lines above, before you do this modification. You may find that one of them was your problem. Unfortunately none of them solve my problem, so I did the t-stat modification."

buy a water pump, do a cooling system flush, replace your radiator cap if it is at all questionable, keep the thermostat.

__________________
Cheers,
Robert

1984 300d Turbo 139k
Replace The Radiator And Remove The Top Hose To Radiator And Fill The Hose With Water You May Have Air In System, A Water Pump Leaks You Have To Add Water. Your Fan Clutch Replace $160.00 Diy

just for the sake of disclosure,
If you were on a long trip with your benz and it begins to run hot 110c
how many of you folks would pull over, call aaa and have it towed to a mechanic.



How many of you folks would take out the thermostat and finish your trip.



I predict that those that choose option A are also those that use mercedes benz coolant....