And when you put it back on, snug it, dont over tighten it.

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1987 300TDT - 195,000 (Original #14 head)
1993 190E 2.3 - 105,000
1981 300D - 250,000

1. do you trust the engine temp gauge? Maybe it's only really 80*C and reading wrong for some reason. Use a IR gun and shoot the head to get a reading.

2. pull the t-stat out to open the flow down there. Pull the upper rad hose engine running - is it gushing out? No? Flush the block.

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Cheers!
Scott McPhee

1987 300D

Fans do not seem to be an issue because the radiator never gets hot. Keep that in mind. Putting it back together and running without a thermostat should take a thermostat issue out of the equation. Stick with it so long as it doesn't cause issues with your family. But really, they are great cars. Cooling issues need to addressed initially on these cars otherwise you will begin to risk the original number 14 head.

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1987 300TDT - 195,000 (Original #14 head)
1993 190E 2.3 - 105,000
1981 300D - 250,000

could you be putting the thermostat in backwards? I know this sounds dumb but i think it is possible if i recall... It wouldn't open if the correct side of the thermostat didn't get hot... just thinking outloud

__________________
1987 300D 180k
1985 300SD 330k Helga
1992 300D Lola 269k- Sold
1986 325 coupe Bessie >300k Original engine(ODO Broke) sold
2006 2500HD Druamax Linda- Tows boat and looks pretty in garage thats about it

Was lying in bed last night and thinking about how cooling system works. So i got a few pics and lets see if I'm right. Because If I am that would explain everything.

First pic is how I found it when I open it the first time. It will only fit in that way because of a little notch that wont let it.

Second and third pic is of notch. Thought it was there so you could not put in backwards.

Forth pic is of how I thought it should go in from the beginning. Because I thought that the second action on the T-Stat " the part on the top " was to redirect the coolant flow. But it dont fit in right because of notch.

I am going to grind away the little notch and try it. Got a good feeling....

Attached Thumbnails

       

__________________
83 300TD Sable 402K " Work Truck "
81 300SD Gray 240K " Loner Car "
04 E320 Blue 90K " My Winter rig "
07 BMW X5 4.4 118K " My Summer rig"
04 Jetta TDI Wagon 168K " Wifes "
08 Toyota FJ 109K " Wifes winter rig "
04 Jetta TDI 120K " Daughters Car "

The side of the thermostat showing in pic 1 goes toward the radiator.
The side showing in pic 4 goes toward the engine.

__________________
85SD 240K & stopped counting painted, putting bac together. 84SD 180,000. sold to a neighbor and member here but I forget his handle. The 84 is much improved from when I had it. 85TD beginning to repair to DD status. Lots of stuff to do.

Well we can see you got the thermostat out.

Have you put in hot water yet?

Dont worry about trying to reverse it, its the right way in your pic 4.

Go and put it in the kettle. If it doesnt open right up well before it boils it no good. You can do that if you dont have a thermometer. Your problem is so bad that as long as it opens well before the water boils it would be unlikely to be the cause.

Is the opening temperature stamped on it?

__________________
Grumpy Old Diesel Owners Club group

I no longer question authority, I annoy authority. More effect, less effort....

1967 230-6 auto parts car. rust bucket.
1980 300D now parts car 800k miles
1984 300D 500k miles
1987 250td 160k miles English import
2001 jeep turbo diesel 130k miles
1998 jeep tdi ~ followed me home. Needs a turbo.
1968 Ford F750 truck. 6-354 diesel conversion.
Other toys ~J.D.,Cat & GM ~ mainly earth moving

In pic one was the only way to put it in. I had to remove the little notch in pic 2 and 3 to get it in like pic 4. I put it in like pic 4 after removing little notch and she still over heats.

Here are some pics of where I have my aftermarket temp sensor put. It reads 190-210 on back roads. lower rad hose still cool.

Attached Thumbnails

   

__________________
83 300TD Sable 402K " Work Truck "
81 300SD Gray 240K " Loner Car "
04 E320 Blue 90K " My Winter rig "
07 BMW X5 4.4 118K " My Summer rig"
04 Jetta TDI Wagon 168K " Wifes "
08 Toyota FJ 109K " Wifes winter rig "
04 Jetta TDI 120K " Daughters Car "

Sorry. I also tested t-stat last night. It opens at 175-180F and second action rises.

__________________
83 300TD Sable 402K " Work Truck "
81 300SD Gray 240K " Loner Car "
04 E320 Blue 90K " My Winter rig "
07 BMW X5 4.4 118K " My Summer rig"
04 Jetta TDI Wagon 168K " Wifes "
08 Toyota FJ 109K " Wifes winter rig "
04 Jetta TDI 120K " Daughters Car "

I am sorry I am not completely up to date on this thread, but for all this testing and modifying etc..

wouldn't it be much simpler to run the engine without the t-stat installed? the engine will run cooler than desired... but its better than over heating.

using regular water during all this dismantling / reassembling is fine. Install the correct fluid once you have a functioning system.

__________________

does your engine have a catalyst on the exhaust, or some other device that might restrict exhaust?

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Was told I cant remove t-stat because she will still over heat when under load. I tried that already. Did not fix the problem. And as for exhaust it does have a cat but she spools up easy and does not seam restricted at all. I had a rig with bad cat, you could hear and feel the restriction.

__________________
83 300TD Sable 402K " Work Truck "
81 300SD Gray 240K " Loner Car "
04 E320 Blue 90K " My Winter rig "
07 BMW X5 4.4 118K " My Summer rig"
04 Jetta TDI Wagon 168K " Wifes "
08 Toyota FJ 109K " Wifes winter rig "
04 Jetta TDI 120K " Daughters Car "

Could the head or block having a crack cause all this? I dont have fuel or oil in Coolant and dont have coolant smell in exhaust. But there's something going on and I have replaced just about everything. The only thing that's not new is the water pump. Mine looks fine but i got to do it. I found a used one 2 hours from here. Going to go get it and give it a try....

__________________
83 300TD Sable 402K " Work Truck "
81 300SD Gray 240K " Loner Car "
04 E320 Blue 90K " My Winter rig "
07 BMW X5 4.4 118K " My Summer rig"
04 Jetta TDI Wagon 168K " Wifes "
08 Toyota FJ 109K " Wifes winter rig "
04 Jetta TDI 120K " Daughters Car "

I thought I needed the T-Stat to redirect the coolant. I will pull her out and try in again. As for the notch I removed from the housing. I had to so the T-Stat could go into the block like pic 4.

__________________
83 300TD Sable 402K " Work Truck "
81 300SD Gray 240K " Loner Car "
04 E320 Blue 90K " My Winter rig "
07 BMW X5 4.4 118K " My Summer rig"
04 Jetta TDI Wagon 168K " Wifes "
08 Toyota FJ 109K " Wifes winter rig "
04 Jetta TDI 120K " Daughters Car "

So gases in the coolant system would make seance. What is " Too Hot " for her anyway?

__________________
83 300TD Sable 402K " Work Truck "
81 300SD Gray 240K " Loner Car "
04 E320 Blue 90K " My Winter rig "
07 BMW X5 4.4 118K " My Summer rig"
04 Jetta TDI Wagon 168K " Wifes "
08 Toyota FJ 109K " Wifes winter rig "
04 Jetta TDI 120K " Daughters Car "