Bench bleeding confusion (1 Viewer)

[BeerM3]

Hey MUD,

I could use some advice. After reading countless articles, especially Coolerman's, on how to correctly bench bleed a MC, I'm wondering if the Napa aftermarket one I purchased is faulty. I stuck it in a vice and tilted it up slightly as has been recommended elsewhere, but from the start the rear reservoir seems to purge just fine but I can't get even a hint of bubbles out of the front.

There's no fluid pushing up into the hose. No hissing or leaking elsewhere. It just flushes over and over in the rear and not a damn thing in the front. I triple checked to make sure the hoses were well below the fluid level and that the fitting & sensors were tight. I sucked the fluid back out and held my finger over the rear outlet which pushes out air, but I can't feel or hear anything being pushed out of the front.

I'm figuring
1) I tilted it too much and should have started more parallel in the vice as is it recommends in the instructions.
2) I have a faulty, crapola aftermarket MC?
3) I'm a noob with brakes and forgot to ______

Has anyone been down this road before and it's just user error?
Thanks


I filled the reservoirs up fully after realizing the instructions were 1/4" from the top, not the bottom. After a minute of slowly pushing the rear was pumping a solid bubble free stream through its hose, but nada in the front. I also tried gravity bleeding by backing off the side screw with the green dot and let it drip for a minute or so. Still no movement in the front.

 

[thebigredrocker]

Do you have a vacuum pump/brake bleeder you could hook up to the front port? Try to suck some fluid through it.

Might not matter, but are you sure you are pushing the piston all the way in? If possible you could bolt the master on your booster and pump the brake pedal to bench bleed it.

 

[BeerM3]

Do you have a vacuum pump/brake bleeder you could hook up to the front port? Try to suck some fluid through it.

Might not matter, but are you sure you are pushing the piston all the way in? If possible you could bolt the master on your booster and pump the brake pedal to bench bleed it.

I don't have a manual vac but I do have a compressor powered vacuum pump (which I was going to try for the first time after bench bleeding).

I felt the piston bottom out a couple of times after getting nowhere with the "short 3/4-1 strokes" recommended in the install guide. I thought about just bolting it up but figured if I can't any kind of bubbling pressure out of the front now I don't know what doing the same thing via brake pedal will do, but I could be missing the obvious?

Thank you for the quick reply.

 

[thebigredrocker]

another option would be to see for yourself why the heck it’s not working. Drain it, pull the snap ring, apply a wee bit of air to the rear output port. This should push the piston back for removal.
Remove the side screw that keeps the front piston up front. Again apply enough air to force the front piston out but not so much it become a dangerous projectile. Inspect bore, ect...I’ll bet the front has a muffed up seal. If not, reinstall with some Sil-Glyde.

If it ends up not working, might try a Japanese made Aisin master from Cruiser Outfitters. Guessing the Napa is chinese made, if so I’d avoid another one.

 

[Mr Cimarron]

I had the same issue with two off brands from rock auto. Gave up and found a Advics on Amazon and that solved the issue. Advics=Aisin. Since I have front disc I used once from a non ABS early 80 series.

 

[BeerM3]

Remove the side screw that keeps the front piston up front

Hang on....maybe that’s the issue? I thought that was a bleed valve but now I think I remember reading about rebuild assembly and having to push in the plunger and then insert that side screw?

Edit: Yep. I re-read the rebuild instructions in the FSM, unscrewed that side bolt, pushed the pistons all the way in and tightened it back up. I now have bubble-free fluid flowing through both after just a few strokes.

Thank you @thebigredrocker . That solves one problem. Now I have to figure out why i have a 7/8" bore MC on a 1/76 FJ40 with all drum brakes...it would appear this should've had the 74-75 side inlet style with a 1" bore. Sometimes I wonder if this thing came from overseas where they didn't go to disc. Or maybe someone downgraded. Who the hell knows. Or maybe I'll be making that front disc conversion sooner than later

 

[thebigredrocker]

Sweet!

Yeah I can’t imagine someone swapping back to front drums unless they did some damage to the 1/76 axle. I think I remember seeing your booster and it is a OEM disc type booster. Does it still have the proportioning valve just below where the master mounts?

Perhaps someone would know based on your VIN if it’s a non-USA. I’m sure if you pinged Living in the Past he could rattle off a hundred small detail’s that would help identify a 76 USA vs. non USA.

 

[BeerM3]

Does it still have the proportioning valve just below where the master mounts?

No proportioning valve, but maybe that’s what would mount to the empty bracket I put back on just for authenticity? It has a single captive nut.

Thanks for the vin heads up. I might reach out to him.

 

[cuencanolenny]

View attachment 1652137

No proportioning valve, but maybe that’s what would mount to the empty bracket I put back on just for authenticity? It has a single captive nut.

Thanks for the vin heads up. I might reach out to him.

I ordered wheel and master cylinders from the USA for my non-USA FJ40 which has FJ45 drums up front. The master cylinder (Raybestos) is like yours, brake lines on top, mine needs them on the fender side. But my question to you is regarding the two large silver knobs on the bottom of the MC? I need to go find two plugs for those locations tomorrow morning.

 

[BeerM3]

I ordered wheel and master cylinders from the USA for my non-USA FJ40 which has FJ45 drums up front. The master cylinder (Raybestos) is like yours, brake lines on top, mine needs them on the fender side. But my question to you is regarding the two large silver knobs on the bottom of the MC? I need to go find two plugs for those locations tomorrow morning.

You list a '70 and '79 in your tag line. If you had a MC that looks like the one above I assume you're asking about the '79? The silver solenoids on the bottom are low pressure brake warning sensors they started using in the states in the early 70's, maybe earlier. They light up the brake warning light in the cab if one of them detects a problem.

If you ordered a MC for an offshore '79 from the USA, then you'll likely have the same problem I did. My FJ40 is a 1/76, and after 9/75 all USA 40's were equipped with disc brakes in the front. Unfortunately the previous owner had replaced my axle with an earlier drum version, and so while I ordered the "correct" MC, it was a smaller 7/8" bore with no residual valve (I had to learn the hard way what that is, they're hidden inside the MC housing where the brake lines screw in) on the front brake line. In short, I had 2-3psi up front vs the correct 10psi necesasry to operate drums in the back and obviously had a hard time stopping the vehicle. The previous owner had added a residual valve in the front circuit of my previous MC, but I didn't know it. It looked like a period correct '76+, but functioned like an all drum MC. I ended up purchasing a USA pre 9/75 MC with a 1" bore and equal pressure needed for front/rear drums. You can read more about it starting here.

 

[cuencanolenny]

You list a '70 and '79 in your tag line. If you had a MC that looks like the one above I assume you're asking about the '79? The silver solenoids on the bottom are low pressure brake warning sensors they started using in the states in the early 70's, maybe earlier. They light up the brake warning light in the cab if one of them detects a problem.

If you ordered a MC for an offshore '79 from the USA, then you'll likely have the same problem I did. My FJ40 is a 1/76, and after 9/75 all USA 40's were equipped with disc brakes in the front. Unfortunately the previous owner had replaced my axle with an earlier drum version, and so while I ordered the "correct" MC, it was a smaller 7/8" bore with no residual valve (I had to learn the hard way what that is, they're hidden inside the MC housing where the brake lines screw in) on the front brake line. In short, I had 2-3psi up front vs the correct 10psi necesasry to operate drums in the back and obviously had a hard time stopping the vehicle. The previous owner had added a residual valve in the front circuit of my previous MC, but I didn't know it. It looked like a period correct '76+, but functioned like an all drum MC. I ended up purchasing a USA pre 9/75 MC with a 1" bore and equal pressure needed for front/rear drums. You can read more about it starting here.

Yes, the '79 had the lines on top. You mention in your other post that you re-bent the lines to fit the side. I guess I could have done that but my local guy had another MC for '75 and while it has the ports for the brake pressure switches it otherwise looks mostly like the one on my rig which uses one reservoir to service both circuits. It looks like the one in your other post. So I will look for a pair of plugs today, worst case I find two switches to fill the holes. You are scaring me about the internal valving thing though.

 

[BeerM3]

Yes, the '79 had the lines on top. You mention in your other post that you re-bent the lines to fit the side. I guess I could have done that but my local guy had another MC for '75 and while it has the ports for the brake pressure switches it otherwise looks mostly like the one on my rig which uses one reservoir to service both circuits. It looks like the one in your other post. So I will look for a pair of plugs today, worst case I find two switches to fill the holes. You are scaring me about the internal valving thing though.

If you have a side outlet MC from either an overseas or U.S. FJ40, 55, etc then I would safely assume it's for front drum brakes, but I can't say that with 100% certainty. If the bore size is stamped on the side says "1" then it's definitely for drums. If it says "7/8" then you may need to investigate. The residual valve under each brass outlet adapter is just a spring and a small piece with holes in it to meter the hydraulic flow in and out. You can unscrew the front one to see if there's one present. Here's a picture of what it looks like.

When people "reverse engineer" their old drum MC for a front disc conversion they just pull out that spring and valve to lower the pressure needed to operate calipers vs drums.

 

[cuencanolenny]

Thanks, I just finished the first go around bleeding, engine off. Let the motor warm up and checked the pedal, need to go around again. I couldn't find plugs for the bottom locations where switches are screwed into. Ended up buying two switches and taking the spade connectors off of them. Taped and installed. The new MC does say 1. The Aisin I took off (and it looks like I need to start shopping for a booster soon) had 7/8 on it, single reservoir.