Unlike my '82 300SD which seems to have a faulty temp gauge, my '84 300td always runs at temps well below 80C - gauge reports slightly above 40C. Today, in 90 plus degree weather in Napa, gauge climbed to close to 80 but still more like 60C! I need to shoot t-stat with thermal gun and take a reading -at this point, beginning to wonder if I have a t-stat that is just stuck wide open (not closing) Any thoughts?

Thermostat, open as you suggest or perhaps absent.

any ir gun will verify your temps. but 50ish c is what you would read with no thermostat...

at 50C you could hold your hand on it without burning it. I think water below 60C wont burn you, if its that cool you have a good cooling system, just replace the thermostat.

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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.
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My 300D did that when I first bought it; the thermostat was installed backwards.

Haha . . yep, stuff like that happens when you buy a used car with certain unknowns . . . time to pul t-stat and check -thanks!

No stat should result in poor cooling performance regardless of weather, running cool in winter and hot in summer.

This case sounds more like inaccurate temp guage to me.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

50C logically should be around 106F... (1/2 of 212... not sure if it's linear or not, but makes sense.) and you can safely touch up to 130F surfaces briefly with your fingertip and not burn yourself. mind you, 130 will hurt, it will not burn unless you submurse yourself in a fluid that sticks to you. a dry surface will not damage you. so if you can touch the metal for an instant, it's below 200... however, if it's above 140, you risk 2nd degree burns with this method of testing... I'd use an IR tool...

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
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My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

thanks - I will be curious to see what happens when I pull t-stat. I have to run an errand today and will confirm temp at t-stat housing with thermal gun