94 Mazda 626, v6 2.5L engine. I have 3 days before the home owner association drops a hefty fine for my non-op vehicle parked in the driveway. I’m doing the timing belt, but have everything figured out for that except this one problem that is halting my entire repair. The #1 idler pulley bolt snapped. I tried to drill out the hole but as you can see by the pictures I messed that up entirely. The bolt is 10mm with a 1.0 thread. I bought a tap kit for 10mm 1.5 thread, figuring I’d just need the different thread bolt. They don’t even sell the correct drill bit size (10.4mm) that the kit recommends in my city so I had to use a 3/8in (9.55mm I think). I failed miserably, I think the opening is too wide and the angles I drilled at were not straight on. Can I replace the idler pulley spacer (think it’s called that) that the pulley sits on? If not, is there any way to save the situation?
I took a couple pictures at angles so you could see the bad drill job and what’s left of it. Any help would be greatly appreciated, going stir crazy over this one problem. Sorry for the phone camera pic quality.
It’s tough getting a hole in a space like this perpendicular to the part. It looks in the photos like the drill bit splayed all over when you bored, and it probably got even worse when the end of the bit hit the hard still-embedded bolt shank.
It looks to me like your only option now without excising the engine is to drill an oversized hole, ap it oversized, helicoil it, and install the new bolt that way. The idler braket should sit on the boss around the positioner, and it should have at least one more bolt holing it, so it’ll probably hold.
So I get a bigger drill bit and dry to do it better, but how will the helicoil insert fit a much larger hole and yet keep the 10mm bolt size the pulley fits onto? Ap it ovesized? Apoxy? When you say excising the engine I take it you mean tear it apart basically. Have valve covers and intake manifold off already. I’m guessing you’d have to take the vavles/pistons apart to get to that area. I’m no mechanic though I’m learning quick.
Thanks for the assistance.
As much as it would kill my pride, at the moment I’d be thinking about the yellow pages & a mobile mechanic. At this point, you’re pretty much past science to art. I’d be looking for an experienced mind & hand to just put me back on the road.
Cigroller may be right. There’s options here but considering what’s transpired so far you may be in too deep. It’s near impossible to explain how to go about something like this.
(A 3/8 bit may be a bit much for a 10 MM hole and tight spots often require an angle head drill. Generally speaking, on something like this you start with a very small bit and drill a pilot hole followed by gradually increasing the bit size, which is usually figured in 64ths.)
I’m sure none of that is helpful but you’re just going through what mechanics go through every week. High blood pressure, foul attitude, bleeding knuckles. and a pounding headache are part and parcel of it.
Norder. This mite work. I have not tried it. Maybe someone on here has. Loctite 37390 - Loctite Form-A-Thread Stripped Thread Repair Kits …
www.summitracing.com/parts/LCT-37390/ If the link don’t work google it.
Sorry that happened.
CAN YOU PUSH YOUR CAR INTO THE (A) GARAGE?
That removes the time pressure so you can succeed athis incrementally.
Garage isn’t an option. Why is 3/8 too much? For re-threading with a helicoil you need to make a larger hole than the original bolt, (3/8s being 9.55mm, original bolt is 10mm, helicoil kit says use 10.4mm drill bit) but I do not need an angle head since I removed the AC pipe lines, removed the right engine mount and raised it a few inches. This way I was finally able to get a drill straight onto it, though clearly I didn’t drill a straight hole due to inexperience. The hole is already too large, the tap bit just changes angle instead of threading further into the hole. This car is going to be junked probably if I can’t fix this since I’ve lost so much $$ to it already. Considering many replaced parts are worth more than pick-n-pull gives for it, I really want to fix it. Anyone tried that Loctite Form-A-Threat oldbodyman mentioned? Is it possible to get a thicker helicoil insert so a larger hole will still fit a 10mm bolt and where the hell can I get a drill bit larger than 3/8ths? Harbor Freight and Home Depot did not have it.
Sorry for the excess of info, trying to address all comments at once. Thanks to everyone here too, this is the best auto forum out there.
any auto parts store or hardware store should have any size drill bit. I would try to see if a 3/8 fine threat tap would work. Can you drill out the hole in the idler pulley for a 3/8 bolt. If you can get a grade 8 bolt 3/8 fine threat and try that.
If you oversize the hole and helicoil it as I suggested, the assumption is that you’ll need to use a larger bolt, and perhaps even open up the mounting holes in the flange of the idler assembly.
OK4450 posted an excellent description of how to get a good hole in a tough spot. Even in a non-difficult (is that a real word?) spot, a pilot hole is standard fare for drill a larger diameter hole accurately.
I already used 3/8ths, which is 9.55mm, which is too small, and ended up chewing the hole out badly when I tried to widen it a little since the helicoil tap was wider than the hole. If I used a bigger bolt I assume you mean widening the idler pulley itself, which I am uncertain how you would go about since the thing rotates. From the sound of it I need to figure out how to go larger, or open the thing up to get at the mounting bolts on the inside. Pretty despondent either way. I could get a 7/16ths drill bit (over 11mm I think) so maybe I will attempt that route. I just hope when I go to re-drill the hole that I don’t mess it up in the same style I did before. Thanks mountainbike and the rest for the suggestions.