Had overheating issues in which the temp reached above 90C so I changed the radiator (cracked anyways and leaking) and all hoses (including the one under the thermostat).

I was very happy results, a cool 82c all day long.

Then I decided to change out the thermostat with an oem 80c rated thermostat, and refilled the system including "blurping" the system. Started to overheat 90-95c again!

So I drilled four 3/8 in holes as directed in the thermostat mods. The trick worked on flat freeway, still kinda on the high around 85c ish. Started going uphill around 40-50 mph at like a 10% grade and started to heat up back to 90c. Turned on the heater and and it went back down to 85c. All of this happened in the morning with an outside temp of 64F. I know it should not get that hot especially in the morning.

Fan is working, and remember that before I changed the thermostat the damn thing wasn't overheating. Maybe put the old thermostat back in?

So what can I do next?

If you run a search in the right way through the forum, you will find that there have been many reports of bad "new" thermostats. You need to use this information to buy the right brand thermostat.

Or, you could put the old one back in. There's no reason any holes need to be drilled in a properly functioning OEM thermostat in my opinion.

Ken300D

Carfaxi is $25 for 30 days.
Autocheck is $25 for 60 days.

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1982 300D at 351K miles
1984 300SD at 217K miles
1987 300D at 370K miles

Change the temperature sender.

Holes are not needed at all. If everything is working correctly it should warm up to 82*c within 10 minutes and stay there all day, especially if you don't have A/C.

thanx guys,

Which one is the temp sender, facing the front of the car, the very front blue sensor or the rear black one one?

It sounds like to me that you are running in a "NORMAL" range. 95c isn't that high.

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My Truck.. 2007 DODGE, 5.9 Cummins, 6spd stick, 4X4. My car..1977 240D, OTHER WHEELS...1955 VW Oval window bug, European Delivery (Holland) with a 1700cc, 2 barrel, Porsche drum brakes. 1939 WILLYS Pick-up. 1967 Triumph 200cc Tiger Cub. 1976 Honda 550F 4cyl Motor Cycle.

motorhead-that is true. And I am assuming that the line above 80c is 90c by the way. But when there is a new radiator and plumbing is should not go that high, especially with a new radiator!


I hope to god it's the temp sending unit because I'm getting really frustrated.

ken300d-By the way, I did do a test and make sure the new thermostat is working by exposing it to temps above 80c and then cooling. It reacts just like the old one.

What kind of radiator did you get?
On a 300D turbo I had a few years ago Stayed at 80* all year round, then when I had to replace it I got some made in Morroco crap from Radiator.com. It then ran at 100* even in the winter...

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Over 21 years I owned several:
w108
w110
w111
w115
w116
w123
w124
w126
w212

BRAND Spanking NEW BEHR OEM EXACT replacement

Did it open as far as the old one? I've read some old threads to that effect on here a while back.

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'83 300DTurbo http://badges.fuelly.com/images/smallsig-us/318559.png

Broadband: more lies faster.

yes exactly the same, they both reacted the same

the mark above the 80 mark is for 100, the next mark is 120, but it's labled. have you drained the block? from the block drain near the starter? and flushed it well? have you done a citric flush?

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 560SL convertible
1987 190D 2.5-5SPEED!!!

1987 300TD
2005 Dodge Sprinter 2500 158"WB
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

Buy one of these and shoot the block with it:

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=93984

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1979 240D- 316K miles - VGT Turbo, Intercooler, Stick Shift, Many Other Mods - Daily Driver

1982 300SD - 232K miles - Wife's Daily Driver

1986 560SL - Wife's red speed machine

I guess I can do that, and what is the citric flush?

citric flush is a flush of the block/cooling system with a solution of citric acid.
search the site for the word citric you will find several threads about it.
follow the procedure and you will have a good cool running car.
John

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 560SL convertible
1987 190D 2.5-5SPEED!!!

1987 300TD
2005 Dodge Sprinter 2500 158"WB
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

thanx vstech I will look it up and let you guys know about my thoughts

-Ive read some of the posts and its really helter skelter on what to do...

take citric acid you buy from ebay
mix citric acid and water (what mix ratio?)
drain radiator and engine block
pour in solution
etch out my brand new radiator and remove rust from the block
run a few minutes with solution and drain. followed by water flush 2x
replace with coolant 50/50 mix?

I understand this helps clean the system, but the car was running cool before. and does etching the entire system promote better interface for heat transfer between the coolant and cylinders? up to 15c? I don't think so.