BLUF: can I safely scrape/clean the crud off my thermostat cover and reuse it?



Had a few hours to kill, decided to flush out the green coolant and swap the thermostat and hoses on my recently rescued 240D. And I was making good progress too... Started at the firewall and worked my way down the system, hose by hose, then the block drain. Not much sediment/rust/corrosion... except for the thermostat cover pipe... it looked pretty horror show.

'Oh well' I think as I proceed to break two of the three bolt heads off... 'Oh well' I think as I wack my dead blow mallet against a strategically placed length of broom handle... 'OH WOW' I think as the horror show cover slowly peels off the thermostat housing...

So, clearly I'm going to PB Blast/torch the bolts and get them out, but what can I do with this thermostat cover? I'm not sure a new hose would seal properly against... well... whatever the heck that is. What do these cost nowadays? (couldn't find it on first search... is it a cover or a housing?)

I get a few days to figure it out, since the crazy mudslides out here have cut me off from work. But I'd really like to be able to clean her up, grab some bolts and get back on the road. No one looks at me when I'm rolling in the prius...

I have been cleaning up some aluminum parts lately and A Harbor Freight soda blaster with baking soda medium will make short work of that part..It will blast away the calcium but is very easy on the aluminum it self

HF sell the baking soda in 50 lbs bags..And you can't believe how good it works on greasy parts too..

I think that what you will find after you clean it up is holes through the area where the radiator hose clamps on..But if it is not to bad, it might seal when you reinstall the radiator hose

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1978 300SD 303400 miles
1983 300D 341270 miles
1980 300SD 320456 miles

It is probably "aluminum oxide", which is a component of many sands and 70% of the moon. Mine looked similar (~1 mo ago), though slightly less corroded. I started with a flat file, then 60 grit sandpaper. You could also chuck it in a vise and use a wire brush in a drill. No leaks at my radiator hose connection.

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1984 & 1985 CA 300D's
1964 & 65 Mopar's - Valiant, Dart, Newport
1996 & 2002 Chrysler minivans

Baking soda medium... Aluminum oxide... I'll have to try to cook something up. Harbor Freight is an hour away on a good day, but these days...

I'll try to file and sand it a bit... I'm not to be trusted with power tools. I'm sure it'll be pitted enough without my grinder or wire wheel.

I'd clean it up completely with a wire brush or blasting. Once it's perfectly clean and you are left with the pitted remains, fill in the pits with JB Weld as of filling dents on a car with bondo, and sand it smooth once it's dry.

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'84 190D 2.2 5MT (Red/Palomino) Current car. Love it!
'85 190D 2.2 Auto *Cali* (Blue/Blue) *sold*
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Soak the part in a citric acid solution or vinegar. The crud may be aluminum oxide, but it may also be a build up of silicates from your antifreeze. Either way, soak off as much as you can before attempting to clean the surface mechanically. If the part is sound, the hose will tolerate some surface irregularity as long as you use a strong clamp.

cheap toilet bowl acid will clean it.Make sure its hydro. acid leave on 30 seconds and rinse.I use one gallon vinegar to flush system when thermostat is removed.Heater on drive for 30 minutes.Then rinse till smell is gone.Better than citric acid.

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1999 w140, quit voting to old, and to old to fight, a god damned veteran, deutschland deutschland uber alles uber alles in der welt

How much does a new neck cost? You will have to wire brush / sand blast this to got a good sense if this can be saved.

And for the record , this isn't a green coolant failure, leave any super wonder long life coolant in the system long enough and the neck would look the same.

That is the cover. The housing is the part which has the broken bolts.

Before you spend any time cleaning up the corrosion, remove the broken bolts. You might be needing the whole lower assembly if you can't get them out.

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“Whatever story you're telling, it will be more interesting if, at the end you add, "and then everything burst into flames.”
― Brian P. Cleary, You Oughta Know By Now

Appreciate the tips! The two broken bolts soaked overnight and one turned right out. The second shrugged off the vice grips...

Still got some time, I'll try to soak and scrape first. Honestly, I haven't dug out the thermostat yet... the cover may be beyond hope.

Also, you shouldn't be using "green" coolant.
You need the pale yellow Zerex G-05 coolant for your car.

And stay away from those mudslides!
Send some of that rain up North here where it will do all of us in CA some good.

Jeff

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1984 300SD 300,000 miles--two tank WVO setup
2.88 diff & 500SEL anti-squat rear end

Got the right coolant plus distilled water and thermostat... been sitting on them for a while. Just figured I should wait until I was ready to ruin the clearly neglected housing bolts. The real question is why didn't I go ahead and get the bolts ahead of time?

This is why I haven't replaced my thermostat....

It isn't a good idea to run with out a thermostat.....I would also advice against flushing the system....If the housing looks like this, chances are the rest of the cooling system looks the same....Flushing could very well open more cans of worms....like the heater core leaking....Can also cause all this build up to break free and clog the radiator....

As was sad, clean it with steel wool, wire brush, sand paper....And if the pitting is really bad use the jb weld to fill in the pits, sand smooth and reinstall...

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So, was scrubbing away with a steel brush... and I noticed a speck of light in the cover.

Well, that's no time to let up so I scrubbed harder. It was a weak spot right in line with the thermostat bypass hole... had plenty of crud caked in there.



Almost thought it was a bad thing... but I'm pretty happy I found it now, rather than powering up a mountain in a cloud of steam...

So... not finding any covers online, and the complete housings on feebay don't look too good...

WOW that isn't good!

This one on the bay doesn't look to bad...

Mercedes Benz OM617 Upper Thermostat Housing PN R617 203 14 74 240D 300D TD CD | eBay

This one isn't shown open but outside looks decent...
Mercedes 617 300D 300SD Thermostat Housing Temperature Sensor Assembly Cap Top | eBay

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