Tstat replace, burped, now runs hot, help?
 

Okay, so the greasecar wouldn't get warm for a long time. Unclipped mono and no change so decided it was the tstat. Replaced it today, car warmed up at idle very nicely. Too nicely.
Now at idle it can get over the 100 mark on the gauge.
Burped by putting nose up (drive is uphill so put it in the driveway) and idled for 40 mins or so. Started getting hot at about 20 mins. I turned the defrost on high and that allowed the gauge to go down. But only to just above 80.

Went to pick up the DD, about 8 miles, and the temp gauge went high again. Went lower with the defrost on. But again, not to 80 mark.

I want to drive it tonight to the bar but don't want to overheat on the hwy.

Any other ways to burp?
Thanks

Remove the upper hose from the radiator and fill the head completely with coolant right to the top of the hose. Quickly reinstall hose.

Drive vehicle.

Problem solved.

I am having a very similar problem with my 240 that all started when i replaced the radiator hoses. I have not be able to improve it at all since. My car will warm my up in less than 2 minutes. It will run fine then all of the sudden temp just goes up to 115 or so then back down to 100 driving around town. I have noticed temp gauge is pretty erradic. It jumps around a bit sometimes pretty quickly. If i run on the highway for a while i can get it to 90 and it will stay there until i come back to stop and go traffic. Running heater will instantly drop temp to 85-90 but then it will climb back up. I've checked everything. I had the radiator rotted out and cleaned, i flushed the system and put new antifreeze in. Checked for air and doesnt seem to have any in the system. This all started when i changed my radiator hoses. It never once went above 85 degrees prior to that. Also, i have NO leaks. I'm stumped. Sorry for hijacking your thread btw.

I'm not.

Read post #2.

Follow it.

did you test the thermo first??

Thank you Brian.
Problem solved!
Took another 3/4 gallon of coolant!

I'm a girl and still get a bit misty eyed every time you come to my rescue.

Good job.

Everybody who has not done this procedure finds the same result........overheating........not enough coolant in the head.

Help is what we do here!

I dont understand how you can get more coolant in that way. As soon as you tilt it down it will spill out. if i take it off right now i'm sure all lose quite a bit. but, i guess it won't hurt to try.

Plus, how does it get past the tstat this way?

Ok, just tried this. As i assumed, the hose was full. I lost more coolant that way from the top of the radiator then i could put in the hose. It took none this way.

You don't understand because you don't realize that you cannot fill the head via the expansion tank. The thermostat is in the way and it prevents filling of the head.

When you fill via the upper hose, the coolant can go nowhere other than into the head..........when the thermostat is closed.

For one thing, i dont have a tank. I have a 240. Only way the thermostat is open is when its hot and under pressure. How can you get anything past that when its closed?

I'd still wager that you've got air in the head. Get the vehicle on an steep upward incline so that the radiator is higher than the head...........and run the engine for 20 minutes.

Then, after it cools, repeat the attempt to fill the upper hose.

two nights ago i removed the bolt in the thermostat housing after it had been sitting for over 4 hours and coolant shot out of there non stop until i managed to get the bolt started. Wouldn't that indicate that the head is full?

...with the heater on full blast.

I don't think he understands that the upper hose connects to the head inboard of the thermostat.

Since you clearly don't wish to follow our suggestions........maybe you've got one of your own that you'd like to try?

If so, let us know how you make out with that.

I didnt say i wouldn't do it, i'm waiting for the car to cool completely. Craig, i understand how it works now in there, i've never seen a setup like this.

It's called a bypass thermostat system. It doesn't work like most systems in US cars which block of the flow of coolant through the block until it warms up. MB's circulate the coolant through the block until the engine heats up and then the thermostat forces water through the radiator and not the block anymore.

If overheating persists despite filling the head via the upper radiatior hose, suspect the thermostat. I went thru two garbage Behr T-stats prior to buying a Stant T-stat at Advance Auto Parts, which then allowed my car to run at the proper temperature.

The thermostat doesn't decide to take a dive at the precise moment the radiator hoses are changed..........it's not that brilliant.

Does the 240 have a fan clutch? It seems that going down the highway and cooling to 90, even though warmer than it should be, could be an issue with not eneough air across the radiator when going slow?

Brian has had a alot of these fixed by doing this, maybe this one is a differant issue? is there a hole next to the t-stat on the 240 like the 300sd? maybe drain it some and refill through the radiator hose?

When I filled mine through the upper hose, I kept filling until the coolant started coming out the rad where the hose would go. Then I put the hose on with just a bit of it open so I could keep filling. Then finished putting on the hose. Still had some burping to do, but it seems good now.

No, the 240 does not have a fan clutch..

Long time no hear from you, leathermang. Hope all is well.

The reason water gushes out when the engine is warm and still not completely full is the air inside is now hot and wants to expand. With no where to expand it, along with the steam from the boiling of the coolant, pressurizes the closed volume of the coolant. You open a path, anywhere, and either hot air and vapor will come out, or, if the hole is below the water line, water will come out. Jim

opening up the heater valve by running the heat full blast may get uncomfortable, but I've found this method works very well since it allows the head to have more than one open passage to circulate coolant in. It needs a high RPM like a couple of miles down the freeway to do this and yes, a Stant thermostat is what I would use too. ;) Makse sure you have no leaks, turn on the heat when you leave the driveway and keep it on full and go. I've never had a problem burping this way!:D

Thanks Jim....I had to take a break...

I think this is a good time to bring up something about overheating in general on 20 plus year old cars...

In the old days when someone rebuilt a block they would take everything off of it...and take it to a place that would boil it out... it would be really clean everywhere... but the part that mattered most in the long run was inside the water jacket of the block ( head counts too ... but focusing on block here)... there is a place typically at the lower back part of the water jacket where the flow rate slows down and stuff is deposited over the years.... and often on these heavy blocks you hear of people renewing sleeves, pistons, rebuilding head...and heading into the future thinking they have a new engine...

Then some summer arrives and they see slowing climbing temperature readings.... and they do all the 1st and 2nd level cures which people suggest....and sometimes that works... but sometimes the fudge area has been taken up by the lack of cooling at the lower part of that old block and those fixes don't work...

If the other stuff does not work.... I suggest taking out the freeze plugs and making something which can be pointed into the lower corners of the water jacket while suctioning water out at the same time... I say it this way because you can't just let the water get into the way and still have enough turbulence and pressure reaching that area of crud.... and it may need to be at the same time as an acid flush happens....and it may need to be done repeatedly to be successful ...
Greg

Ok all this was done twice. Head will NOT take any more coolant through upper radiator hose.

Ok...go test it and report back....

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.:)

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.

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

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

ginny,

go to my post here:
http://www.peachparts.com/shopforum/showthread.php?p=1801278&posted=1#post1801278

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

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.

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?

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.

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

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

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.

:)

It goes this way:

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.

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.

Welp, then my tstat is in backwards. But BOTH cars has tstats in backwards.

Gonna go get dirty now, back in an hour or so with results.

Thanks Craig.

It's not that unusual, when I bought my car it had the thermostat backwards too. In my case, the car was running too cool. Let us know what happens.

I didn't think you could close the cover without damaging the thermostat if it was in backwards.

In the attached photo, "D" is port from which hot water exits the engine, the outlet marked "A" is hot coolant from the engine going to the radiator. "B" is coolant returning, presumably cooled from the radiator. "C" is normally a mixture of hot coolant from the engine and cooler coolant from the radiator, going back into the engine. With the engine cool the thermostat is pretty much as shown in the photo. The circuit involving the radiator is closed off at the return line "B" so there is no flow through the radiator. Warmed coolant is short circuited back into the engine (going from "D" to "C" as the arrows show in the photo) to speed up the engine coming up to operating temperature. As the coolant warms up the path to the radiator is slowly opened. When the engine is hot, the path back from the radiator is fully open and the "short circuit path" is closed, forcing all the coolant flow through the radiator.

If you look at the housing and the thermostat, there is a surface on the fixed part of the housing that seals on the moving part of the thermostat (closes to close off the short circuit path) that is not covered by the spring. If you put it in backwards, you should inspect the sealing surfaces of the housing and the thermostat. I do not believe the thermostat is the same axial length on either side of the wide, seating flange that locates the thermostat in the housing.

By analysis, if the thermostat is in backwards it is highly unlikely the thermostat will close off the "short circuit path" for coolant to bypass the radiator. As a result, even if the closed when cold part opens, the flow through the radiator will be at something less than the maximum flow as the coolant in the engine gets hotter. This may make the water coming from the radiator colder, which may cause the thermostat to close, giving you fluctuations in temperature.

Sorry about the prior mis-diagnosis, but you have to understand no one can make a diagnosis at a distance when there are basic parts installed backwards. Good luck, Jim

Turned the tstat around, put coolant back in and drove on the hwy.
Now stays right around 85-88*.
Think we can call this fixed?


Now to tackle the air that I think is getting into the primary filter.
Hard starts and when I pull up the filter I can see bubbles.

Not at all!
I never expect any of you all to know absolutely from 1500 miles away what might be wrong with a car. All we can do is throw out ideas about what might be the problem based on prior experience.

I put the tstat in the same way it came out. Backwards. On BOTH cars. Interesting but it happens I'm certain. It's all good now and I learned a great lesson.

Also need to change out a headlight today, and add ATF. It's a little low.