C90 Thermostat - PeachParts Mercedes-Benz Forum

VegeMan · #1 04-25-2007, 01:42 PM

Anyone know where to get a C90 rated thermostat for a 1981 300D? I want to run my WVO MBZ a bit hotter (good or bad idea

) to allow for a quick warm-up and switch over to vegetable oil.

VM

vstech · #2 04-25-2007, 02:14 PM

the higher temp thermostat will not get your water hotter any quicker... it will just take longer for the thermostat to open.
John

rrgrassi · #3 04-25-2007, 02:56 PM

IIRC, the NAPA ones are 90c by default.

VegeMan · #4 04-25-2007, 03:04 PM

Quote:

Originally Posted by vstech

the higher temp thermostat will not get your water hotter any quicker... it will just take longer for the thermostat to open.
John

The C80 rating is when the thermostat is fully open. However, while the car is heating up the thermostat partially opens at temperatures below the rated temp. If you can delay this partial opening then would not the car reach operating temp faster? Maybe the difference in time would not be noticable, but in theory it sounds good.

VM

vstech · #5 04-25-2007, 03:12 PM

if that is so, they your theory may be sound, I was unaware of this. I doubt there would be any measurable difference. make sure that whatever temp tstat you put in, it does not have bypass holes in it.
John

rrgrassi · #6 04-25-2007, 03:15 PM

A partially opening t-stat would take the car longer to heat up, IIRC, especially in winter. Driving them heats them up faster.

VegeMan · #7 04-25-2007, 04:34 PM

Exactly. If the partial opening of the tstat occurs at a higher temp, then the car will reach operating temp faster (right?). It is my understanding that tstats do not spring open at their rated temp, but slowly open as the temp rises. If this slow opening is delayed, the vehicle will start cooling later in its warming up process.
VM

#8 04-25-2007, 10:53 PM

Use an electric heater.

sailor15015 · #9 04-26-2007, 12:25 PM

Quote:

Originally Posted by VegeMan

The C80 rating is when the thermostat is fully open. However, while the car is heating up the thermostat partially opens at temperatures below the rated temp. If you can delay this partial opening then would not the car reach operating temp faster? Maybe the difference in time would not be noticable, but in theory it sounds good.

VM

Buy a new proper "C80" t-stat and boil it on your stove and see when it opens. You'll be surprised. 80 is not the temp at which it is fully open, but rather when it begins to crack.

Ether · #10 04-26-2007, 03:47 PM

Quote:

Originally Posted by sailor15015

Buy a new proper "C80" t-stat and boil it on your stove and see when it opens. You'll be surprised. 80 is not the temp at which it is fully open, but rather when it begins to crack.

That is correct. I did this experiment on a new one last weekend and 80C is when it begins to open. It is not fully open until well above 90C.

With a brand new radiator and new Tstat my car is running between 90C and 100C so I would like to find a Tstat that begins to open at around 70C. But all the parts stores I've been to seem to only have 80C or 90C available. Anybody know a source for lower temp tstats?

vstech · #11 04-26-2007, 09:55 PM

if your car is getting to 100 with new radiator and tstat, I would verify the tstat is opening, at the correct temp, then look into a bad water pump, or a dirty block water jacket. I would also test the head for a blown gasket.
John

#12 04-27-2007, 08:43 AM

Quote:

Originally Posted by vstech

if your car is getting to 100 with new radiator and tstat, I would verify the tstat is opening, at the correct temp, then look into a bad water pump, or a dirty block water jacket. I would also test the head for a blown gasket.
John

I agree, mine runs a 80 - 90C or just a little above, it shouldn't be getting close to 100C unless it's under a heavy load for some amount of time (i.e., big mountain on a hot day).

Ether · #13 04-27-2007, 09:17 AM

I'm pretty sure it's an issue with the tstat, though I won't know for sure until I pull it and check. I will be curious to see how the one in there now compares to the new one that i tested last week.
The car was actually running too cool prior to installing the new tstat. This past winter I had to go with cardboard in front of the radiator in order to get up to decent operating temp.