Overheating caused by thermostat or the water Pump.

Driving on the Freeway on a 10 mile trip. About 7 miles out I was getting smell like a small amount of Oil on an exhaust manifold. Never thought to take a glance at the Coolant Temp Gauge.

Got to were I was going and noticed no leak and I did not look for what I thought was an small oil leak either.

Same thing happened on the way back but when I got home there was a definite leak from the Water Pump. Again I never thought to take a glance at the Coolant Temp Gauge (old age issue?).

About 5.5 years ago I replaced a Japanese Water Pump (it must not have been the original because a blot was broken off) which had been on the car when I bought it and lasted 7 years. I replaced it with a Gates Water Pump which as mentioned lasted 5.5 year before leaking.

After some research I found out hat GMB Water Pumps for my Mercedes are made in Japan that the pics look the same as the one I originally removed. I one and installed that today.

Since I was so in-attentive concerning the overheating I decide I needed to install a high coolant temp alarm. My Thermostat Housing has an empty part on it that is not drilled out but clearly is a spot for a sensor.

I removed it and found that my Thermostat was physically broken, see the attached picture.

Now I am wondering if the Thermostat caused the overheating and that killed the Water Pump Seal causing the Water Pump to leak.

Note my issue but when you overheat for what ever the reason the overheating sometimes ruins the wax casual in the Thermostat. So it is a good idea to replace it or keep a close eye out for it to fail.

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84 300D, 82 Volvo 244Gl Diesel

I would think it's a 50/50 chance that the thermostat caused the water pump to fail. For all we know the water pump just aged out. But glad you were able to make it home instead of being stranded on the freeway.

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1983 123.133 California
- GreaseCar Veg System

If the rest of your cooling system looks like that thermostat, you have much bigger issues at hand.

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Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

I always had the proper amount of antifreeze in it but it likely was like that when I got it in 2007. Never had any overheating issues since the last water pump leaked 5.5 years ago.

When I was a Kid people out here put only Water in their Cars unless they were going someplace like up to the local mountains where it could be below freezing. By the 1970s that changed.

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84 300D, 82 Volvo 244Gl Diesel

Concerning the color of my coolant system. Many years Back when it over heated the first time I had put in some Bar S Block Sealant that as what appears to be copper in it. And after several weeks I followed that up with some GM type radiator sealant pellets which also give the coolant that reddish stain.

I am going to back flush the system but don't plan on using any other type of chemical flush.

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84 300D, 82 Volvo 244Gl Diesel

Pretty gnarly looking system... to be honest, I’d consider a citrus flush ASAP

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1981 240D 4sp manual. Ivory White.

Signs of a neglected cooling system for sure. Coolant hasn't been flushed every few years, who cares if it's the correct antifreeze ratio if the corrosion inhibitors tagged out long ago.


It's hilarious to note that the OP is blaming the water pump for a failed thermostat and the failed thermostat for the leaking water pump. I guess we're gonna gloss over the rust debris and sludge in his cooling system literally ERASING the carbon water seal as it runs. I'm frankly surprised he got 5 years out of it with the mud he's running for coolant. The damage to the thermostat is likely due to a poor weld that finally just let go, not helped by corrosion and poor state of the coolant in the cooling system.

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Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

It is hilarious that you did not note that I claimed I was not sure which caused which. Of course you are free to believe what you wish.

There is no mud in the system there is a light coating of colored material.

I never do periodic chemical flushing on any of the vehicles I have owned since 1968. However, I have known neighbors that flushed only to have the loosed crud plug up their radiator and continue to do that for months and months after the flush.
What ever you coolant system looks like inside if it is function normally it is not an issue.

I have driven the car since 2007 I must be doing something right.

All of the work i do on vehicles is purely related to functionality and keeping it on the road. I never have an intention of keeping the vehicle in pristine condition.

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84 300D, 82 Volvo 244Gl Diesel

Here is another broken thermostat.

https://www.benzworld.org/threads/thermostat-failure-is-this-common.3069093/

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84 300D, 82 Volvo 244Gl Diesel

Not really, brake pads can be driven down to the metal before they quit functioning and tear into the rotors. Brake fluid is also supposed to be changed periodically but many don't care as long as the car stops.


Oil is supposed to be changed but frequently isn't. Eventually, the engine is shot.


Just because the damage can't be measured, doesn't mean there isn't any. Simply changing the coolant and flushing with a garden hose goes a long way to keeping crud from building up. It also prevents electrolysis from eating into the heater core.


Not doing basic maintenance leads to a condition where every system needs work to bring it back into full functioning. What I call PPM leads to periodic break downs like you have with your cooling system. It is the difference between doing the maintenance when convenient or repairs when forced to because of a break down.


This reminds me of an old girlfriend. She would put tape over the check engine light and ignore it as long as the car still ran.

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85SD 240K & stopped counting painted, putting bac together. 84SD 180,000. sold to a neighbor and member here but I forget his handle. The 84 is much improved from when I had it. 85TD beginning to repair to DD status. Lots of stuff to do.

It doesn't look that bad.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

Looks pretty grody. Besides, the only reason the OP is doing anything is because he was forced to.


Broken fan belts are another perfect example of PPM. Most of the time they don't break. Leave them on too long and they will possibly at a very inconvenient time like when you're going down the interstate and have just passed an exit.



That funny smell is antifreeze that's leaked from between the head and block or from the crack in the head depending on how hot the engine got while the driver went a little longer on a $20 worn out part.

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85SD 240K & stopped counting painted, putting bac together. 84SD 180,000. sold to a neighbor and member here but I forget his handle. The 84 is much improved from when I had it. 85TD beginning to repair to DD status. Lots of stuff to do.

...would a man select a girlfriend who is old?

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84 300SD
85 380SE
83 528e
95 318ic

You are going by the color. The color is caused by the radiator sealant tablets I put in and the Bar-S Block sealer I used years a go on it (it has copper particles in it). That is what is coating stuff.

I did back flush the Black, radiator and heater core all done separately.

When it is assembled I will fill it with water run it sum so it is nice and hot and drain and then renew the coolant.

The bigger worry is this is the 2nd time it has been over heated (previously around 5.5 years ago). I am worried about warped head and an head gasket issue. But, one problem at a time.

Apparent the Heater Hoses on the fire wall need renewing as they did not feel go. I bought a set of those many years ago so I guess I am finally going to use them.

I am also getting a new Coolant Recovery tank since I has patched the original one several years ago.

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84 300D, 82 Volvo 244Gl Diesel

Here is some pictures of what I had previously put in the coolant system.

The CarGo sealant: "Seal-Up is a unique combination of modified sodium silicate (liquid glass) and copper. Whilst in the bottle or mixed with water, it remains liquid with the copper sinking to the bottom.

Seal-Up cures by exposure to the atmosphere and turns into a solid ceramic substance enriched with copper. The copper has two effects: first of all it strengthens the weld and then it transfers heat, thereby helping to eliminate hot spots. Seal-Up bonds with all metals (and even some plastics) and builds a ceramic-metallic weld, which is extremely strong, high heat resistant and permanent for the life of the engine.

Seal-Up will easily repair holes of up to 1mm diameter and cracks of any length up to 0.5mm wide (both of which would result in major coolant loss). Seal-Up, once cured, will withstand temperatures of up to 540ºC (1000ºF) and pressures of up to 3000 psi. It is designed to expand and contract with the radiator or block and is also heat conductive in order to eliminate hot spots. Seal-Up should also be used immediately after an engine rebuild to ensure that the head, gaskets and other weak points in the cooling system are properly sealed. This will help to avoid the frustration of having to 'fix the repair'."

So the stuff has Copper in it. When you are down at the Auto parts store take a look and shake up the Bottle and see what color it is.

The next one is the Radiator Sealant Pellets which are also reddish colored.

Over the years a good deal of the reddish colored particulates stick to the surfaces inside of the coolant system. Hence the rusty look.

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84 300D, 82 Volvo 244Gl Diesel