Tstat replace, burped, now runs hot, help? - Page 3 - PeachParts Mercedes-Benz Forum

Knightrider966 · #31 03-22-2008, 03:41 PM

Quote:

Originally Posted by imagesinthewind

Okay, I was wrong, I'm not fixed.
I was on the hwy today and the gauge went to 110. I turned on the defrost to get some of the heat off and it went back down to 100. Driving more, the gauge went to 90, up to 105, down to 85, up to 100. No rhyme or reason to the fluctuation.
The gauge just goes up and down, with the heat on, with it off, at high speeds at lower speeds.
When I got home I unplugged the mono to default to highest heat and let the car idle. It went back down to 85 with the defrost on (mono unplugged) and when i turned it off the heat the gauge is creeping up slowly. 8 minutes or so and still at about 95.

The good news is the WVO tank is now showing 152*. Which is the reason I changed the tstat in the first place, the car AND the oil couldn't both heat up before. Gauge would show 65-70 and the oil would show 100-105. When the heat was turned n the gauge would drop and the oil temp would drop. (all oil references here is WVO not engine oil).

Should I jack up the front of the car to get the head higher or put in another tstat?
I'm on an incline now but maybe not high enough?

The tstat came out of the parts car. It's new too, and the DH told me this morning that his car always ran right around 100* since no one told him that was kinda high he never through twice about it. Shop did his tstat, not him. So you think the tstat is bad?

Thanks

Well if your temp guage was not acting like that before, then yes, I think the thermostat is defective or the incorrect operating range. My 240D and my 300D both run at 85*C in Arizona in the summer heat!

So there is a problem here somewhere. I would believe that the temp swings your looking at are now caused by the opening and closing of a questionable T-Stat. I would replace it with a Stant at 85*C or 170*F and report back.

ascalise · #32 03-22-2008, 04:56 PM

No improvement whatsoever. In fact it seems to get hotter quicker now. But the strange this is the gauge will jump back down to 90 pretty quick sometimes now but will only stay there about 20 seconds. I went to advance and bought a stant tstat. I will install that later and let you guys know what happens.

JimSmith · #33 03-22-2008, 06:31 PM

Rapid temperature fluctuations are not being caused by a thermostat that is opening and closing quickly. Thermostats fail by wearing out to the point where they no longer respond to coolant temperatures. They can stick open and give you a car that won't heat up unless it is at full load in Death Valley in the summer, or they heat up instantly because they won't open.

Rapid temperature changes come from air failing to be purged out of the system and being circulated in the block and head. When a bubble goes by the temperature sensor you likely see a different temperature than when water is running by. And, in the engine, when the air bubble is moving along, or sticking in one place until it grows big enough that the water flow begins to drag it along, you get a hot spot. When water comes by again you get good heat transfer and the engine cools but the water gets hot. And may boil, making another bubble.

The answer, unless your thermostat is stuck closed, is to vent and vent and vent. It has been noted that the thermostat is supposed to have a small hole drilled in the flange. This hole must be located in the housing at the high point. The thermostat is not installed "level" so one side is higher than the other. This hole goes on the high side so it will let bubbles through, even when the thermostat is closed.

So, I would try venting. I drive mine up onto a pretty steep hill on my property. You could try using ramps under the front wheels if there is no convenient hill. I will typically do the job as described earlier, but, then I fill again after putting the hose in place, and with the engine running and at temperature. At this point I fill through the radiator cap (240Ds don't have a reservoir) with the heat on full and let it run like that for a while, checking and filling.

Good luck, Jim

ascalise · #34 03-22-2008, 06:50 PM

Ive done this at least 6 times in the last week. With ramps, jacks, hills, you name it.

79300sdtd · #35 03-22-2008, 06:56 PM

ginny,

go to my post here:
http://www.peachparts.com/shopforum/alternative-fuels/217221-tstat-fixed-but-wvo-second-tank-not-getting-hotter.html?posted=1#post1801278

kerry · #36 03-22-2008, 07:08 PM

Temperature senders also sometimes fail. Are you confirming the temperature fluctuations with a non-contact thermometer?

ridgerunner · #37 03-22-2008, 07:41 PM

Don't take this the wrong way; if you put the thermostat in backwards (its been done) you'll have the exact same problem. High temp, flucuating temp etc.
Just a suggestion.

imagesinthewind · #38 03-24-2008, 01:03 PM

Tstat is in correctly, still not staying in range.
Replaced coolant with 50/50, still not staying in range.
Will buy new tstat today and replace again.

Can I reuse the coolant?

Eric Eliel · #39 03-24-2008, 07:15 PM

Try testing the thermostats on the kitchen stove in a pot of water. I have found that some brands will open wider (and therefore flow more) than others. You can also test for the proper opening temperature. Verify the quality of the thermostat operation first before you start tossing thermostats and wasting time and money.

t walgamuth · #40 03-24-2008, 10:10 PM

The stove test is not always definitive. I had one recently that seemed fine on the stove but didn't work right in the car.

Tom W

Palangi · #41 03-24-2008, 10:29 PM

What works for me is the 75 degree Wahler thermostat from an old 450SL. This will take off 5 to 10 degrees compared to the "correct" thermostat. The gasket that comes with this one will not work on a 617 though. Use the gasket appropriate for your year of 617 (probably the kind that wraps around the rim of the thermostat).

http://catalog.worldpac.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=2BW1BVKT22BW1BWD7M&year=1975&make=MB&model=450-SL-001&category=G&part=Thermostat+Kit

imagesinthewind · #42 03-25-2008, 01:39 PM

Okay.
Stant Tstat, 50/50 blend coolant, filled in upper hose and then in resevoir.
Drove 72 miles (to bar and back) and twice the needle touched the bottom if the 120 numbers, not quite to the overheat point but close enough that I was ready to pull over and stop the engine.

I took the first 'new tstat out of the parts car. The spring part of the tstat was in the part of the housing that you can hold in your hand, the 'left hand' part.
When I took the tstat out of the 81, the tstat was in the same way. I assumed that this is the right way to put one in, spring part in the left part of the housing.

Is this wrong? Tom's car (parts) was running hot all the time. The Tstat of the 81 was bad, not getting the engine to temp. Could BOTH tstats been put into two cars wrong?

Help!
I'm ready to put the broken one back in since it's getting warm here and driving the car with the tstats I have will just lead to overheating.

#43 03-25-2008, 01:45 PM

It goes this way:

imagesinthewind · #44 03-25-2008, 01:55 PM

I saw that. So is the left side of the diagram the front of the housing as you look at the engine?

And Can I reuse the coolant in the system now or get new, again.

#45 03-25-2008, 01:58 PM

Yes, the left side of the photo is the front of the engine (the part you remove). There is no reson not to reuse the coolant unless it's contaminated somehow.