Hi gearheads, "long time, first time." Thanks for all your advice over the years.

I just got a 300D ('83, U.S. —*and I think this is relevant) and — hating myself —*broke one bolt in the thermostat housing. About an inch or so is exposed, but WD-40 and a vice is not doing the trick when it comes to wiggling it loose.

My car-minded father proposes that we just remove the entire housing — the better to use penetrating oil, or heat, or (in extremis) drill the thing out of the housing or get a new one.

The three attached hoses were a cinch to remove, but there's a final bolt —*I think the "forward" one on the A/C bracket — that is almost impossible to unscrew, thanks to the EGR unit. That unit and even the offending, shiny hose is also proving difficult (for two amateurs) to get out, thanks to a square washer or nut we cannot reach.

And though there are many tutorials about how to replace a thermostat, there are relatively few about how to remove the entire housing, in case I'm missing something obvious!

I will save my questions about how to flush out the rusty, green coolant from the engine block for another, brighter day. Thanks for any tips or advice!

If the bolt is protruding, warm the housing around the bolt not the bolt, put penetrating oil on it and walk away. Repeat this several times. Don't breathe the smoke and/or fumes while doing this.

After a couple of days of soaking put vise grips on the bolt and hit the bolt at the same time you try tightening first and then loosening it in VERY VERY small increments. Work it back and forth.

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer

As SB said but dump the WD40 and use something called Kroil.

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Jim

X2 ^^^

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer

Get a better penetrating oil. Kroil or PB Blaster. With the PB blaster look for the word "catalyst" on the label. If you don't see the word catalyst on it you have the PB blaster version of WD-40 and that is not what you need. Her in CA PB Blaster is sold at Home Depot.

Us a propane torch or small handheld butane torch to heat the housing let it cool a bit and spray the penetrating oil and let it cool. Spray some more after it cooled.

Alternat the heating cooling and spraying.

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84 300D, 82 Volvo 244Gl Diesel

Some have done this.

https://www.youtube.com/watch?v=INDQQ7gBuIc

Some have also used to the welder to build up an extension that you can get a vice grip on.

The heat of the welding takes the place of the heat from a troch.

This has a better view.

https://www.youtube.com/watch?app=desktop&v=PQ0YkPb3oVs

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84 300D, 82 Volvo 244Gl Diesel

Thanks all. So I do have to get the Kroil. Will try! And it sounds like it’s not worth removing the housing.

Patience is the key to removing the bolt. On non-daily drivers I've warmed, soaked and impacted broken bolts for up to a week with success... patience.

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer

Removing the housing isn't difficult, you'll just have a gasket to replace when you're done, which means cleaning the gasket surface also.

I've had this same issue before, and I just removed the housing and carefully drilled out the broken bolt. It wasn't too bad.

You may go this route if you can'r remove the stud by methods others have mentioned.

Thanks again, all! Just one last question, for a noob: how much heat are we talking (on the housing)? I’m working with a propane torch and a piece of sheet metal to shield hoses, etc.

Remove the hose. When you get the hose off you might find considerable pitting under the hose.

I don't know what to tell you on the heat. There is no way I have ever had to measure the temp on such objects. I can say I have never melted anything so far.

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84 300D, 82 Volvo 244Gl Diesel

I am going by what I have read on this forum. Kroil has been said to be superior to the PB Blaster and since I have used PB Blaser myself I can say for sure it is a lot better than the old school liquid wrench penetrating oil.

When I looked for Kriol out here, I found none and when I tried to Oder some years ago they would not ship it to CA. I am guessing Kriol has some substance in it that CA does not allow.

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84 300D, 82 Volvo 244Gl Diesel

Read up on a 50/50 mix of ATF and acetone as a penetrant.

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer

Most HVAC supply houses stock kroil
It can be ordered online as well.

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 560SL convertible
1987 190D 2.5-5SPEED!!!

1987 300TD
2005 Dodge Sprinter 2500 158"WB
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

Careful with heat.
Aluminum parts dont cooperate with it.

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 560SL convertible
1987 190D 2.5-5SPEED!!!

1987 300TD
2005 Dodge Sprinter 2500 158"WB
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!