617 turbodiesel.

Previous owner is a family member and swears the T-stat is "not old." Last few weeks the car has seemingly never come up to operating temp. This morning was quite cold (18F) and on my 40-mile drive, temperature gauge never got over 60C.

Heat is marginal in the car but I know the monovalve is bad and I plan to fix that issue this week.

Are there other ways besides the presence (or lack thereof) of cabin heat to tell if I'm looking at a cold-running 617 or just an inaccurate temp gauge? Or would you recommend just replacing the T-stat?

It's either the thermostat or the gauge. Since you describe less than stellar heating I would suspect the thermostat. They do get stuck open. My 300CD was when I bought it and had the same symptoms. A new thermostat solved it and now it has plenty of heat. The part is cheap and it is an easy one to replace...just be sure to get all of the air out of the system when you refill it. There are plenty of threads about that.

Your lack of cabin heat could also be caused by the auxilliary coolant pump being bad. I think that when the monovalves fail they usually fail open causing excessive heat...not sure though. I do know that if the aux coolant pump isn't working it can cause weak cabin heating.

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Marty D.

2013 C300 4Matic
1984 BMW 733i
2013 Lincoln MKz

OK, how do you bleed the air out? Is there some trick? Got a good link?

__________________
81 Mercedes 300SD 289k.......SOLD
82 Mercedes 300CD 252k......slow ride

82 mercedes 300 SD...mi Unknown
83 Mercedes 300D ????ksniff..gone too
84 Mercedes 300D 148k........SOLD
85 Mercedes 300TD 386k and holding some one elses project

I take the top hose off and fill that first, then the rad. I think thats the best way.

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-Randy Wakefield

1969 220D 4 speed (parts car)
1976 280C
1976 280S
1981 240D 4 speed (parts car)
1982 300D
1983 300TD (Ivory)
1983 300TD (gold)
1985 300TD (gray)
1987 190D 2.5
1970 280SEL (sold)
1977 240D 4 speed (sold)
1974 280 (rusted to death)
---
1927 Chevy 4 door sedan
1938 Chevy 2 door sedan
1950 Willys Jeepster
1955 Studebaker President 4 door
1977 Ford F250
1979 Glastron 17'
1948 John Deere A
1960 John Deere 2010
1979 Satoh S650G
--
2000 Bichon (Doby)

Well, first, try the "Sans-a-Stat" Just kidding!

Best way to bleed it, is to burp it. With the front end raised up, fill the system through the upper radiator hose. Take the hose off of the radiator, but leave it hooked up to the t-stat housing. This will also fill the radiator since the hose level is higher than the top of the radiator. Keep filling until some coolant dribbles out of the upper radiator hose connection on the radiator. Then connect the hose back, add some coolant to the tank, start the car and check for leaks.

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RRGrassi


70's Southern Pacific #5608 Fairmont A-4 MOW car

13 VW JSW 2.0 TDI 193K, Tuned with DPF and EGR Delete.

99 W210 E300 Turbo Diesel, chipped, DPF/Converter Delete. Still needs EGR Delete, 232K

90 Dodge D250 5.9 Cummins/5 speed. 400K

Gone and still missed...1982 w123 300D, 1991 w124 300D

Thanks.....I would have just tried filling through the tank.

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81 Mercedes 300SD 289k.......SOLD
82 Mercedes 300CD 252k......slow ride

82 mercedes 300 SD...mi Unknown
83 Mercedes 300D ????ksniff..gone too
84 Mercedes 300D 148k........SOLD
85 Mercedes 300TD 386k and holding some one elses project

No prob. Search the forum for "burping" and you will see quite a few posts on that.

__________________
RRGrassi


70's Southern Pacific #5608 Fairmont A-4 MOW car

13 VW JSW 2.0 TDI 193K, Tuned with DPF and EGR Delete.

99 W210 E300 Turbo Diesel, chipped, DPF/Converter Delete. Still needs EGR Delete, 232K

90 Dodge D250 5.9 Cummins/5 speed. 400K

Gone and still missed...1982 w123 300D, 1991 w124 300D

Thermostat. Heat on max temp at full blast should hurt your hands should you dare place them close to the vents, and you should hear the laments of your suffocating passengers

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1985 CA 300D Turbo , 213K mi

it could be new and still bad.

it happens occasionally.

tom w

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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.

I wouldn't condemn the 'stat just yet. If the engine makes 60C., it's not stuck open.

If you fix your monovalve and get proper heat, the problem is the gauge. If you don't get heat (and you won't get much at 60C.), then I'd look to the thermostat.

If you can borrow an infrared temperature gun, it would provide your answer in about two seconds. The cylinder head typically runs 180-190F.

The records on my car I bought this past July indicated T-Stat work done in May 2006. Well, my car would not get above 60 degrees on a cold day either. So, I checked the t-stat. That so called t-stat work was just a removal of the t-stat and placing the housing back on "sans a t-stat"

__________________
RRGrassi


70's Southern Pacific #5608 Fairmont A-4 MOW car

13 VW JSW 2.0 TDI 193K, Tuned with DPF and EGR Delete.

99 W210 E300 Turbo Diesel, chipped, DPF/Converter Delete. Still needs EGR Delete, 232K

90 Dodge D250 5.9 Cummins/5 speed. 400K

Gone and still missed...1982 w123 300D, 1991 w124 300D

I like that. A new term. I've got a "sans-a-stat" installed on my vehicle.

Thanks! Yeah! With the new "Sans-a-Stat", cold running is virtually guaranteed in cold weather. I wonder how many of those I could sell?

__________________
RRGrassi


70's Southern Pacific #5608 Fairmont A-4 MOW car

13 VW JSW 2.0 TDI 193K, Tuned with DPF and EGR Delete.

99 W210 E300 Turbo Diesel, chipped, DPF/Converter Delete. Still needs EGR Delete, 232K

90 Dodge D250 5.9 Cummins/5 speed. 400K

Gone and still missed...1982 w123 300D, 1991 w124 300D

If you talk it up properly, you can probably sell a ton of them. The guys who have that "fuel" conditioner that attaches to a fuel line and breaks up the fuel molecules are probably retired by now...............

You got that right. I saw the "Fuel Master" magnet on the Harbor Freight catalog. That all rates up there with the "Fuel Pills", which was just brown colored mothballs, and Diesel Secret Energy. The fuel pill people got shut down, luckily.

I have an idea...You make up a Stainless Steel "Sans-a-Stat" gasket that replaces "the old, worn out, out of date" T-stat housing gasket, and we can supply it to Lovecraft, guaranteeing "full coolant flow" to his "maintenance free" WVO filter system. I think $29.99 plus S+H is a fair price...

__________________
RRGrassi


70's Southern Pacific #5608 Fairmont A-4 MOW car

13 VW JSW 2.0 TDI 193K, Tuned with DPF and EGR Delete.

99 W210 E300 Turbo Diesel, chipped, DPF/Converter Delete. Still needs EGR Delete, 232K

90 Dodge D250 5.9 Cummins/5 speed. 400K

Gone and still missed...1982 w123 300D, 1991 w124 300D