since I don't have the cash for much needed new tires & alignment, i figured it would be the perfect time to rebuild the t25 & verify operation of wastegate mod.

well, 2 of the 4 bolts holding the cartridge to the housing snapped off, leaving me to dremel out the remains.

clearly my pilot hole was a little too small, boy am i learning a lot.

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1991 300D

You shouldn't have done that. But you probably know that already.

There are several possible fixes. You can try to back it out with a tiny chisel - usually, if you can get it to move even a tiny amount it'll loosen right up. You can try heat and a tiny chisel. If all else fails you'll need to find a shop that does EDM (electrical discharge machining). The EDM can actually follow the exact contour of the threads and leave a perfect hole. I have no idea what that costs in your area.

Dan

I believe you are speaking of the Bolts that go through the bearing housing to the exhaust housing.

Did you snap off the Ezee out type tool or a Tap during re-threading?

It is quite common for turbos that use bolts in a similar manner for them to rust/corrode in and snap off when you try to remove them. Note that that would not have happened at all if when it was assembled a Never-seeze type compound had been applied to the bolt threads.

For others one of he ways to decrease the chance of shearing the bolts is to do the best you can to put a punch over the top of the bolt head and give hit the punch several good wacks with a hammer.

Next is penetrating oil and heating the are the bolt threads into with a Propane Torch.

If they won't turn off normally after that. If possible use the Box end of the wrench and take a Hammer and tap with the hammer on the wrench in one direction of rotation and then the other direction. If it loosens a bit get some penetrating oil in the gap formed and heat again.

Having already been broken applications of penetrating oil and heat several times trying to get the oil to seep down into the threads followed by the proper sized drill for the Ezee out type tool would have been next.

As you indicated the Hole needs to be drilled down the center and the right size for the ezee out your chances of success decrease. I have always had trouble with the drilling part of the job.

Ezee outs are usually so hard they cannot be drilled through with normal drill bits.

Not sure if it would be cheaper for you to get another Exhaust housing from one of our Members or taking it to a shop that specializes in burning broken bolts and so on out.

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84 300D, 82 Volvo 244Gl Diesel

Tedious job.

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84 300D, 82 Volvo 244Gl Diesel

Another option I've used but can't recommend:

With an oxy-acetylene cutting torch you can light the torch and point the flame DIRECTLY down the hole that the tap is in. Once the tap is nice and red or even hotter you hit the oxygen lever and keep your face out of the way. This will blow the now-molten tap out of the hole. It's dangerous and will screw up if the heat isn't applied directly in line with the broken tap (the hole will easily veer off). When I've done this I've subsequently oversized the hole and either tapped oversize and installed a bigger screw or Helicoiled the now bigger hole. Ugly but it can work. This is sort of a poor man's EDM.

Dan

the holes drilled for easy outing turned out to be just off-center enough so they didn't want to turn, so i stopped, afraid of snapping it.

that probably would have been the time to use some heat, but i was alone in the metal fab shop & i didn't want to mess with their torch set-up

the dremeling was less tedious than i expected. the shop was air conditioned when it was hot a balls outside, so that was nice. i used grinding bits intended for chainsaw sharpening, it went fairly quick.

on monday i will take the carnage to one of the old-timers to see what can be done

i agree that starting over w/another housing might be best, but at the moment there is no car parts budget untill a new build comes through. will put out feelers in parts wanted

much thanks for the helpfull advice

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1991 300D

I've done that type of repair with a plasma cutter (as well as oxy/ace). If you're careful, you can make a lot less mess with the plasma cutter.

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1984 300TD -- summer daily driver
Many others that aren't Mercedes...

I'm sure you're right but I don't have a plasma cutter so my options were limited.

Dan