Stripped rear caliper bleeder | GTAMotorcycle.com

Stripped rear caliper bleeder

Priller

Well-known member
So the rust on my old RC51 isn't done with me yet. You folks helped massively with that, so I'm returning to the well...

After dealing with a seized swingarm bolt due to corrosion, I have started with the braking system. I was tearing down the rear caliper for a rebuild when I noticed the bleeder was quite rusty. I tried to remove it, and it immediately became clear that it wasn't going anywhere easily. I soaked it in yet more Liquid Wrench, but it made no difference. After getting impatient (my usual downfall), I tried twisting it out slowly while backing off every few turns like a tap. No dice. It fought me the whole way, and once removed, it became clear that some of the threads from the caliper decided they preferred sticking to the bleeder. What's left behind is a mess. It looks like the previous owner (or one of the 8) had cross threaded it at one time, so I don't think tapping it to the original size is feasible.

20201122_113804.jpg

So what are my options?

I'm thinking the following:

- helicoil
- bleeder repair kit
- just buy a new caliper

I'd prefer to avoid the latter, though they'd not super expensive (the shipping on eBay is, though - twice the cost of the caliper in many cases).

The helicoil is the most appealing because it stays closest to stock, but I don't know if the thread will interfere with the seating pin on the end of the bleeder bolt. There's also residual corrosion inside the caliper that would have to get cleaned up to restore the seal.

The bleeder repair kits look good, but it's a tiny little caliper, and I'll have to measure carefully to see if it'll fit. I'm not optimistic, considering the space available.

Does anyone have any experience with this that can save me a headache? Or should I cut my losses and order a replacement...
 

J_F

Well-known member
Site Supporter
you mention corrosion inside
I'd strip the caliper to see how big a problem that is first
that may determine what you do going forward
 

ToSlow

Well-known member
Site Supporter
even if you run a thread chaser in that you will still need to disassemble the caliper completely to get the debris washed out
 
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Priller

Well-known member
It's already apart, piston, seals, everything. The only corrosion is in the bleeder recess. Piston looks perfect, cylinder looks good, the threading for the banjo bolt is so pristine that it's still gold.
 

J_F

Well-known member
Site Supporter
I'd try a thread chaser and new bleeder screw

just my opinion (but I was on the tools for > 10yrs)
Liquid Wrench sucks - it's a can of diesel fuel

Moovit

edit:
if you are saying the taper inside the caliper where the screw seats is corroded
if you see pitting on that surface the caliper is toast
 

Mad Mike

Well-known member
Replace the caliper.

You’ll never get the bleeder seat lined up after drilling and tapping.

I know caliper shops don’t even try to repair a caliper when bleed screw threads are compromised.
 

Priller

Well-known member
Replace the caliper.

Blah. I figured this was how it was going to end up, was just hoping for a less expensive (and wasteful) solution. If I can clean the seat without damage, I'm going to try retapping, just in case it's not as bad as I think, but the odds of success are very slim.

Hi ho, hi ho, it's off to eBay I go...
 

bitzz

Well-known member
If you are going to try to chase the thread you will need a #3 tap. A #1 or taper tap won't cut in a shallow blind hole
I would take a #3 and grind the end off... which leads to your next problem: anything you ram in that hole is going to destroy the sealing surface for the bleeder screw. Drilling for a insert (helicoil ) will encounter the same issue. There is special drill for that hole, that drills, taps and creates the seal seat at the bottom all in one go. I would use an end mill, not a drill.
It looks like a M8 bleeder. You could drill and tap for a M10 bleeder.

If OP doesn't want to get involved in this mess he could get in touch with Midland Caliper 416 750 2479. Harry does good work and has the specialized tools for the job.

NEXT TIME: Heat is your friend. Heat the bleeder til it is almost cherry red, a couple of light raps with a hammer and it will just spin out.

I know caliper shops don’t even try to repair a caliper when bleed screw threads are compromised.
Funny you should say that. I worked at Speedy Brakes in Mississauga in the '70s, rebuilding calipers. 90% of my time was dealing with seized bleeders. If you broke off the bleeders we would deny your core charge. If you left the rusty, seized bleeders alone you got your core charge returned. We didn't care how bad they were, they just had to have intact bleeders.
 

J_F

Well-known member
Site Supporter
taps are for cutting new threads
you can use them as a repair tool
but that's not their purpose

a thread chaser has no point and will not go near the sealing surface in the bottom of the bore

2018_08_16_04.jpg
 

GreyGhost

Well-known member
Site Supporter
taps are for cutting new threads
you can use them as a repair tool
but that's not their purpose

a thread chaser has no point and will not go near the sealing surface in the bottom of the bore

View attachment 45976
Agree, I would be using a thread restorer not a tap. Nothing to lose. It either seals and you're good or it doesn't and you are ordering an expensive caliper. I would try the almost free solution first.
 
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Mad Mike

Well-known member
If OP doesn't want to get involved in this mess he could get in touch with Midland Caliper 416 750 2479. Harry does good work and has the specialized tools for the job.
Midland won’t touch it. They will remove an intact bleeder, but not one that needs reseating.
 

Priller

Well-known member
The plan was to grind the first three threads off an old tap I have and then mark it short of full depth so I could get close without damaging the seat, but it's all a moot point. I tried cleaning the seat with pipe cleaners, and it's pretty rough. As a last attempt, I sprayed some rust dissolver in and let it sit for a few minutes. End result is the rust from the bolt has swelled and damaged the soft aluminum seat, so unless the entire thing gets re-milled, it's always at risk of leaking.

I found a clean looking replacement on eBay for $70 all-in, and it's even in Canada so no criminal brokerage fees from the UPS/Fed Ex mafia. I'm running this with a CRF450 master, so the reservoir is tiny and I don't want to take chances with even the smallest leak on the track...

Thanks, all. The adventure continues. Keep a lookout for the next episode of, "Look What's Rusty Now!"
 

Trials

Well-known member
New or used calliper.
Regular heli-coil won't seal well enough, it's more like a spring then a plug.

Or just thread it and plug it and deal with no bleeder there. <- that's the cheapest option that is certain to work.
 

Priller

Well-known member
New or used calliper.
Regular heli-coil won't seal well enough, it's more like a spring then a plug.

Or just thread it and plug it and deal with no bleeder there. <- that's the cheapest option that is certain to work.

Used, but appears to be in decent shape:

Screenshot_20201122-162832_eBay.jpg

For the price and under the circumstances, I'd rather have something I can top up easily.

At least the (much) more expensive front calipers seem to be coming apart with less fuss. I'm a bit worried about this piston, though. The rest look fine...

20201122_163148.jpg
 

Roadghost

Well-known member
I would have just drilled an tapped the old caliper from 8mm to 10mm, then stuck in a different sized bleeder. I have a drawer full of different size bleeders from my old cars dating back to 1967.
 

GreyGhost

Well-known member
Site Supporter
I would have just drilled an tapped the old caliper from 8mm to 10mm, then stuck in a different sized bleeder. I have a drawer full of different size bleeders from my old cars dating back to 1967.
Do you think you can hand drill and tap that hole with enough precision for that pin to seat? Or do you have the bleeder taps that also recut the seat?
 

Roadghost

Well-known member
Do you think you can hand drill and tap that hole with enough precision for that pin to seat? Or do you have the bleeder taps that also recut the seat?

You don't tap it all the way down to the taper. Drill down enough to clean out the mess, the drills will leave a taper, then tap it enough to get the bleeder in. Remember most bleeders are tapered at the end. If you drill right through you won't have a true bleeder, you'll have to plug the hole with a bolt and it will be difficult to bleed.
 

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