With the engine running while relatively cool, can you see coolant circulating when you remove the radiator cap? Did you burp the system after replacing the water pump? Is your heater putting out heat?

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

I have one of these and use it to burp every engine that I change the coolant on.

Amazon.com: Lisle 24610 Spill-Free Funnel: Automotive

This lets you run the engine with the funnel full of coolant, and as the engine heats up and bubbles rise through the funnel, coolants drops in and fills the system.

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I choose to be happy, even when the Mercedes is being awkward, lol

So I tested my thermostat (on the stove with thermometer method) and guess what it did not open. So I am pretty sure the new thermostat is the culprit I just have a few more questions when I put the new tstat in there is no arrow?

1.How do you know which direction to point towards the firewall?

2.Also when I popped off the tstat I noticed old green coolant sitting there. I just refilled with Zerex G-05 which is orange. Check out the pics.

3. On the tstat housing there is a wire going into the temp sensor and a black wire just sitting there should that be plugged into anything?

If this tube is plugged "BY-PASS PIPE, Banjo pipe MB# 1152000058", the system is very difficult to bleed, and will overheat until the air is out..


DIY Water pump Bypass hose replacement, OM615, 616, 617



.

Yeah check that little banjo hose thing, that goes from the block to the head.

As for the green coolant, did you flush everything completely when you changed the thermostat? When I did mine I started by removing the thermostat, then I drained the radiator, after that I drained the block, and to finish I flushed everything I could with the hose (radiator, since I had the upper hose off because it needed replacing, and then through the thermostat housing, pretty much everywhere I could until it came out clear from the drain in the block)

After all this is ran at/slightly above 80*C, before it would barely get to 60*C since the t-stat was opening up too early. I'm still having some slight overheating at times, which I have suspected for a while is being caused by that little banjo tube.

Anyway, good luck figuring it all out!

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1982 300D Turbodiesel, daily driver. Mods so far: Fram 8038 paper filter, 4 brake light mod, Gen II w126 (front) rotors/calipers, boost turned up to 12lbs, non-egr manifolds, water/methanol injection, 4-speed manual
1980 300SD Turbodiesel, project car, nearly ready to hit the street

1974 240D, New paint

The old green coolant still present indicates no circulation was there after the first thermostat change I believe. Thats if you refilled the first time with other than green. Also check the thermostat you pulled out originally for a very small bleed hole.

I have found that a few times the one I removed had one or a variation of it with a closing plug for one way flow or possibly air release as I do not know everything. The chinese replacements did not but caused me no grief so far.

I always try to remain observant so if a problem of some form rears up..I can take anything unusual into consideration. I really enjoy working on cars as a pastime.

Unfortunatly even at age seventy this year I cannot seem to find enough time from other commitments. I originally told the wife when retiring at age 50. Retirement being not having to go out and earn money to sustain a decent standard of living that is. I have been so busy since then perhaps I should go back to work for the break. Originally I had mentioned to the wife if early retirement did not work out I could always go back to work.

I was always fortunate in changing out thermoststs. Usually a very simple exercise.Even here.

Then there was one of the family buggies last week. The thermostat cover neck had oxidized solid around the two studs retaining it. There was too much wiring harness etc there to use heat. So off came seven coolant hoses. The coil pack and a neck sensor I thought might be damaged from the heat.

Then I unbolted the main thermostat housing from the block. Fired up the torch and heated it up. Took three times before I could get the parts separated.

There was a little distortion to the neck flange part for my efforts. So got to level the flange as well.. This is one thermostat change that took longer than the fifteen minutes I assumed it would.

In the rust belt where we reside you do tend to run into corrosion problems of some sort fairly often. Here if you did not have ox/ac heat on hand I would not touch a car.

You didn't answer my question about burping the air out. How did you refill the system? You need to refill thru the upper radiator hose into the block or you'll get an airlock. Ideally, the car should be pointed uphill on the refill. It's really common for these engines to overheat when replacing the coolant if you don't take steps to avoid an airlock.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

Yes to me it is always a concern that The coolant refill is really getting into all the places. Unfortunatly never basically doing the same line of engines when I change a thermostat I am unaware if it is harder to refil than the last one was.

Old mercededs diesels can retain a large air bubble in there. I would probably raise the front end if refilling one. Not that it is absolutly required.

Lots of questions flying around. Mine is: how did you drain the coolant? Through the drain plug or did you just pull the lower hose?

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Mac
2002 e320 4matic estate│1985 300d│1980 300td
Previous: 1979 & 1982 & 1983 300sd │ 1982 240d

“Let's take a drive into the middle of nowhere with a packet of Marlboro lights and talk about our lives.” ― Joseph Heller, Catch-22

i drained the coolant by unplugging the radiator drain plug. I refilled the coolant by jacking up the front filling up the radiator and running the carto operating temp with radiator cap off. when i put my new tstat should i first drain the block?

when i refill my coolant im going to fill it thru the upper radiator hose with the front jacked up.

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1978 300D non turbo

If you are doing it all again I would follow this procedure and clean the whole system out.

Mercedes Citrus Flush

i put another new tstat in (tested first) filled with g-05 and distilled water on an incline first through the top hose then filled the radiator. It is still overheating im stuck.

Any ideas on a next step. Im going to measure the actual temp with a infared temp reader, but any other thoughts would be helpful.


Thanks for all the great replys!

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1978 300D non turbo

Time to pull the water pump and make sure the impeller is still attached/not rotted.

I had a car come into a Ford dealer that I worked at years ago and nobody could fault find the overheating. I scratched

my head, then yanked the water pump and found the impeller laying in the block.

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I choose to be happy, even when the Mercedes is being awkward, lol

i just put in a brand new water pump. The only thing i can think of is the water pump had different style propeller. The original had a spiral design the replacement has bent fins. But i dont think that would cuase such overheating? Or can it?

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1978 300D non turbo

Verifying the gauge indication would be an excellent course of action.

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When cryptography is outlawed, bayl bhgynjf jvyy unir cevinpl.