Technical Help I drilled into the coolant jacket!

Well every now and then we all do something stupid. Sometimes it’s REALLY stupid, and that’s where I am right now.

I’m installing a set of offset dowel pins to correct some runout in the bellhousing and naturally the pin that is hardest to access is stuck in the block. I made up a drill jig and carefully drilled the pin right on center. I wanted to ensure that I got through the pin and knew that I’d be sacrificing a little cast iron from the bottom of the hole. Well I was overzealous and I pushed the drill right into the coolant jacket.

There’s no way to plug it as far as I can see. I’ve got some ideas and I’d like to hear from you fellas.

First I’m thinking I file a groove around the edge of the pin and coat it with Permatex gasket maker, like a makeshift o-ring. Next I could machine a small countersink on the bellhousing hole and slip an o-ring over the pin.

Does anyone else have any practical suggestions before I set the whole shop on fire?

 

Drill the hole a bit deeper and tap and install a pipe plug

weld it closed

small frost plug?


Make a custom dowel pin / pipe plug

 

You said the hole is into the water jacket, but in that last photo it looks like oil running out of the hole?

 

It’s definitely coolant

 

If the new pin has a tight interference fit it shouldn't leak. Think soft plug. Put some sealer on it before you tap it in

 

It sounds like you're using regular dowel pins but re-drilled for the pin position you need (as opposed to leaving the hole where it was and using an offset dowel pin). Adding the pin and sealing the hole should be pretty straightforward. You just need to be sure you know how deep you can press the pin in without going too deep and plugging the coolant channel.

 

I don’t dare move the hole location, not with my luck lol. I made a pair of offset pins for this application.

 

It does have an interference fit, maybe not as tight as what I pulled out but definitely within a tenth or two.

 

That would be great but extremely difficult to pull off. Remember the pin needs to be .012” offset and would have to clock just right after installation.

 

Welch/freeze/core plug in first to seal then your offset pin

Loads of engines use small tap in plugs at the end of the galleries.

 

PS you can use on non setting sealant on the pin as well as a double measure

 

Slather it in Loc***e and don't look back. If it has to be clocked use the stuff that gives you a little time, as some sets up immediately. You could also dab some JB in the bottom of the hole after a good cleaning then go about your process. Last idea, if there's a lot of concern then get everything super clean, put in your dowel, then just like copper plumbing you could sweat the base with solder. Or maybe even tin the dowel 1st, drive it in and clock it, then sweat it in. Clean is the Supreme element. Metal prep like used on sheetmetal before prime works real well on cast iron. It's not a some's good more's better thing, you can watch it go virgin clean very quickly then rinse and dry. Relax, enjoy the adventure. You'll be fine.

 

Since its in a bad location, put in a new pin with Green Loc-***e and open up the hole in the bell housing, then drill a second hole down where you can get to locate with.

 

These dudes have you covered. I would consider future you if possible. This was a bear to get out this time.
I'd lean toward a tap and plug or JB in the hole (with or without the welch plug) so that whoever deals with it in the future isn't cursing you and your offspring trying to get the dowel out. Yes, a leak is going to ****, but it will **** more with the dowel permanently installed.Since the bottom of the hole is not set up with material for tapping, you might consider a shorter dowel. Stinks, but the dowel is just to align, not to hold load.
Doing it in place sure makes this harder, so I offer best wishes on repairing it no matter what you decide.

 

There are starting, bottoming, and plug taps. If careful, a standard Allen set screw becomes a plug when using a plug tap. Common in the industry when pipe thread is not wanted.

 

He could remove the freeze plug to be able to check the depth of the pin. I would make an offset dowel threaded on the end that goes in the block and tap the block so it could thread into it. Use loc-***e on the threads to keep offset at proper spot.

 

If it were me, I'd use your dowel, but rather than loc***e, which will work just fine, I'd use JB Weld as the dowel sealant. Clean it really good (either way with loc***e or JB), knock the pin in and get on with your day.
I did something similar on a transaxle case, and it lasted for nearly twenty years...or until I destroyed the case by other means.

 

I can check the full depth after I remove the remaining fragments, which is the ‘sleeve’ that can still be seen. There wasn’t much material behind the dowel pin but I’ll get a more accurate measurement.

I’m hesitant to do any work to the block unless I absolutely have to. It is still in the car and the firewall is right there. I have no problem making custom fittings such as these offset pins.

Lots of great suggestions here and I really appreciate all of them, thank you all. I’ll get back out there tomorrow evening or the weekend.

 

Don't use offset dowel pins, instead, tap the leaky hole for a bolt, remember to machine off the threads that would stick out of the block so the bolt also acts as the new dowel pin. Now drill the dowel pin holes in the bellhousing oversize for an offset bushing, on the surface of the bellhousing that bolts up to the block machine a 'step" in the bellhousing dowel pin hole to keep the offset bushing from falling out. When you machine your offset bushings leave a "step" to match the "step"in the bellhousing, also, make your bushings closed at the end that sticks out of the bellhousing (it will look like an upside down "cup", that way you can machine a "hex" on the end of the bushing so you can turn it as needed. Hope this helps.

 

I know you do not want to hear this. Pull the engine. Drill the hole out and tap to take a pipe plug big enough to drill the original hole in the center. Put the plug in with some sealer, machine it flat and start over.

 

You’re right, I don’t want to hear that even though that’s the best option. I’ll see how I feel this weekend.

Last night I pulled out the remaining piece, cleaned the hole with a shortened .370 reamer and measured the depth. Seems the wall thickness in that spot was about .200”.

 

Is the hole still the correct size for the dowel pin or now bigger?

 

https://goodson.com/products/fluid-weld

I think that I would clean up the hole and use this product to reinstall the dowel pin, especially if it is an interference fit
the coolant isn't under that much pressure....and this is a pretty high temperature product.
You can pressurize the coolant system after the new down pin is installed and leak check with soapy water....
I have used this on cast iron taper plugs repairing busted Ford A and B decks....it works fantastic
a cast iron taper plug would be another way to go....
I have the plugs and taps, they are pricy especially for plugging one hole....
I would sent them to you on loan.....
PM me if you decide to go that way

anyway, my thoughts

Larry

 

If you had room to drill, I think you can run a tap using the appropriate wrench. Shorten the tap if necessary. Good Luck!

 

winduptoy beat me to it

 

Yes the hole is still pristine, like a June bride.

 

How did you find out that you need an offset dowel?

 

So, lick it and stick it. Just sayin...

 

@shorrock I used a dial indicator to check for runout, it is off about .025”. Apparently the older transmissions use ball bearings and they can tolerate a bit more runout. The T-5 I have uses tapered roller bearings and from what I’ve read, runout needs to be less than .005”.

Years ago I modified this bellhousing to accept a 5 speed and I’m finally getting around to doing the job now.

 

If your new pin is still a press fit I don't see how it could leak.