Differences in thermostats - Page 2 - PeachParts Mercedes-Benz Forum

Tymbrymi · #1 02-02-2007, 12:32 PM

Quote:

Originally Posted by stephenson

What if tstats had evolved the same way - imagine a sensor based electric system that measured water in 3-5different places, also using inputs from other thermal sensors and position sensors to anticipate loads so that as you start up a hill, the tstat opens in advance of the load -maintaining temp +/- 1 degree ALL THE TIME. If it is gonna be electric, why not make the coolant pump electric, too (I think this is already in the works with move to higher voltage systems) - and then the pump could work with the sensor system and the tstat to completely control thermal issues without belt drive - it could even operate off the battery when the belt does through itself .... pretty cool!

They're working on that now.... automakers are trying to get every last bit of MPG out of their big engines (one day they will figure out small displacement and turbos....), and the system you've described is one of those efforts. Why take HP (as little as it is) to pump water when you don't need to? IIRC, a big beneifit of an electric water pump is also to allow the engine to warm up quicker (and that is an emissions requirement).

Actually, I think there is a production vehicle with an electric water pump already... the Colorado maybe? Don't know if it has any funky control algorithm though.

ConnClark · #2 02-02-2007, 01:32 PM

I have had thermostat problems too. My thermostat that the car had when I bought it started to fail and kept temps from exceeding 60 degrees C. I replaced it with a new one and it would seem to hold temps at 85 degrees C. The previous one used to keep temps at just above 80. The new one started to fail recently and its not even a year old. If I keep my heater on full blast I can still maintain about 83 degrees C temps in the winter. If I turn it off however the temps slowly climb to 100C. Temps rise to the 80 degree range quickly then creep up slowly from there.

I have bought a new one from napa. Last night I drilled 3 3/32 holes around the edge in the new one. This will provide some flow but it won't interfere with warm up much.

I do have something to say that I haven't seen stated here yet. If you have an engine that has run at 80 degrees C all its life and you change thermostats to one that causes it to run at 90, it will cause excess wear due to thermal expansion. You want a thermostat to hold a temp closely no matter what to limit this.

stephenson · #3 02-02-2007, 11:48 PM

Brian,

Perhaps the fan clutch? Have heard of a lot of radiators being replaced with no real change ...

softconsult · #4 01-07-2007, 07:07 PM

I was on K6JFR's website looking at his section on Water Wetter. He describes assuming that his water to coolant ration should have been correct given that the car had been serviced at the dealer. He found it to be incorrect.

I have the same scenario. Car had it's 90K dealer service at 99K and coolant was changed. Think I will buy the little Prestone ratio tester and check it out.
Maybe the coolant to water ratio is too high, which would cause the engine to run slightly hotter than I was used to in the 124's.

Steve

Steve

123euroowner · #5 01-07-2007, 08:01 PM

Which stat will make the motor run warmer...my 617 seems to run much better at an elevated temperature..and which makes it run coolest

anarchy · #6 01-09-2007, 01:32 AM

i am so confused on what thermostat to buy, at the moment my car doesnt have one, it hasn't had one for 4 months because the ones ive put in make the car over heat or run at 120

MarkM · #7 01-09-2007, 05:53 AM

Buy a Wahler from Auto Zone...it runs coolest...just above 80C

t walgamuth · #8 01-09-2007, 07:57 AM

Quote:

Originally Posted by anarchy

i am so confused on what thermostat to buy, at the moment my car doesnt have one, it hasn't had one for 4 months because the ones ive put in make the car over heat or run at 120

i bet you put them in backwards.

tom w

retx · #9 01-09-2007, 12:24 PM

well i just ordered one from dieselgiant. does anyone know off hand what the ones he sells are rated at? just curious.

also, other than the tstat working or not working correctly, not being the right temp rating for the right car, or having being modified....i have a 93 ford e150 van, it runs "hot" when on tour. but its really not. even when not loaded down and just using it as a daily driver...it reads hot. its because the temp sending unit is not accurate anymore. so even though the engine/tstat/coolant is correct and running cool and smooth, the gauge is showing hotter. the location of this sending unit, cost and the fact that its a van, being hard to work on, i have decided not to change it. have had it for four years, numerous tours across the states and have had no issues with it. just a thought.

Shorebilly · #10 01-09-2007, 03:06 PM

Quote:

Originally Posted by t walgamuth

i bet you put them in backwards.

tom w

Although I did not make the attempt, from what I saw when I changed my thermostat about 10 days ago......I don't think it can be inserted backwards.....do not think that the thermostat will clear the housing if inserted backwards.....

SB

BUT....don't forget the arrow....

t walgamuth · #11 02-01-2007, 08:07 PM

Quote:

Originally Posted by Shorebilly

Although I did not make the attempt, from what I saw when I changed my thermostat about 10 days ago......I don't think it can be inserted backwards.....do not think that the thermostat will clear the housing if inserted backwards.....

SB

BUT....don't forget the arrow....

oh yes they can be put in backwards!!!!

don't ask how i know!

tom w

Old300D · #12 02-01-2007, 08:18 PM

I just don't buy the excuse that the temperature gauges are not accurate. It's easy to say, but I've never seen one that really was. All the gassers I've ever had sat right on the thermostat setpoint regardless of operating conditions. The Mercedes diesel seems to be a completely different beast that varies it temperature depending on load -- mine sits around 80C +/- 5C until I get up to freeway speeds, then it rises, and if I'm cruising up a hill, especially at high altitude, I can get close to 100C.

I also hear the thermal load for a diesel is higher, but I cannot understand how. A diesel is a more efficient engine, and in theory should shed less heat to the radiator as more heat is used doing work -- it has a cooler exhuast and better mileage than a gasser.

nhdoc · #13 02-01-2007, 10:01 PM

So, what is the purpose of the arrow on the thermostat anyway? I used to think those were on the models which had the little bleeder valves in them but I noticed there is an arrow on the MB one I just removed even though it has no bleeder...why does the arrow need to point up? It seems like the thermostat is symmetrical and there is nothing special about it when it points up.

864Lightning · #14 02-02-2007, 11:37 AM

While we are on the subject of cooling,,, try blowing out your radiator fins with compressed air . Apply the air from the back , fan side. I was amazed at the amount of crap that came out of my 79SD..

I have to do this all the time with my tractors when I am bush hogging.. My tractors have screens to catch the big stuff , but a radiator will get clogged with dust over time.

tobybul · #15 01-09-2007, 02:05 PM

There are a lot of factors affecting the quality and performance of products including tsats as we all know.

In theory, it should work as designed... but thats in theory and may not always work as designed. Thats why not same products perform the same. Variables include workmanship, material, installation, other components in the cooling system, etc.

As said, Dieseldiant has a pictorial on drilling holes to help adjsut the temp. I believe that one big factor (covered in a discussion in this forum) affecting cooling performance is the oem radiator vs aftermarket. Based on the performance of my 84D (aftermarket rad) vs my 85D (oem rad), I beleive that the oem rad does not cool as well. The cooling performance of the rad has a direct bearing to the engine temp. I don't think this means that the oem rad is no good. Its just the the non-oem maybe more efficient (more surface area?).

Of course the stat is a key element. The oem stat is designed to work with the other oem components in the engine.

my 2 cents