new hydraboost doesnt have plug

[big block 88]

We are redoing our entire brakeing system on our parade truck after a brake failure caused by a broken master cylinder. We have replaced all wheel cylinders shoes brake kits master cylinder had new hard lines made, the issue is with the hydraboost.

We have several hydraboost units for the M35 but they are all the same and they are smaller in size than the original hydraboost but all ports and mounting locations are correct except one thing... The original hydraboost has a plug in on the front of it the new unit has no port for this plug in.

What is the plug in for?? Has it been eliminated with newer models and revisions?? Do we have the wrong hydraboost units?? Any help will greatly appreciated, thank you gentlemen.

 

[hoop]

http://www.steelsoldiers.com/deuce/40509-long-vs-short-airpack-pics.html#post447963

 

[big block 88]

Thanks for the link but no-one there seems to even acknowledge the plug in on the end.

 

[Heavysteven]

Can't answer but your
Talking about this plug on the left bottom looks blue?

Edit, I believe he is reffering to the plug on the back used for lubrication

 

[clinto]

http://www.steelsoldiers.com/deuce/...8.html?highlight=airpack+plug+lube#post673718

 

[rlwm211]

If you are talking about the plug on the old style air pack versus the new style the major difference is the length of the air piston assembly and the way it mounts on the Slave Cylinder.

The older style airpacks have a "J" Tube that connects the air control valve and the end of the cylinder where the air would come in to pressurize and move the piston. This style has a cap on the end where the "J" Tube connects and it is removeable by taking six nuts off.

The new style has a cylinder that that looks more like an oil filter cannister and it bolts to the Slave Cylinder assembly and ha no cap on the end next to a J Tube.

If this is the case, your old Air Pack is the one you removed and you have several of the "new style" air packs.

The plug is where some elect to lube the air pack assembly with some air tool oil.

I rebuild the older style airpacks and to be honest oil in the air piston misses the part of the air portion of the air pack that needs the lube as well.

I would remove the inlet air line, squirt a few pumps of air tool oil in, and then reconnect it and cycle the air pack a few times. This allows the air control valve to be lubricated as well as the main air piston.

If you are unsure, a photo would be very helpful in figuring this out.

RL

 

[Wildchild467]

would squirting oil in the inlet also lube the pushrod that the piston is connected to? i have often thought about that and wondered how that gets lubrication. squirting oil in the back of the air pack is good and all for the air cylinder part of the air pack, but that pushrod seems like it could use a little bit once in a while or once a year. thoughts? or is just squirting oil in the air inlet line like a "one stop shop" for PM'ing the airpack?

 

[rlwm211]

The pushrod ends up inside the slave cylinder bore and the BFS will lube it.

RL

 

[big block 88]

Can't answer but your
Talking about this plug on the left bottom looks blue?

Edit, I believe he is reffering to the plug on the back used for lubrication

So in your picture the plug in I speek of would be on the far right of the pic if it didn't cut off. It has 2 wire that run up to the harness on the driver side frame rail.

Sorry guys I'm trying to understand and figure it out I'm just havin a slow day I rekon.

 

[big block 88]

would squirting oil in the inlet also lube the pushrod that the piston is connected to? i have often thought about that and wondered how that gets lubrication. squirting oil in the back of the air pack is good and all for the air cylinder part of the air pack, but that pushrod seems like it could use a little bit once in a while or once a year. thoughts? or is just squirting oil in the air inlet line like a "one stop shop" for PM'ing the airpack?

I would agree, our master cylinder failure was caused by the rod going in when the brakes applied and never came back but the brakes released and would not apply and pedal was on the floor.

I would assume rust or corrosion caused this, or it could have been maybe just a fatigue issue.

 

[big block 88]

I found an image provided in the link I was given above.

I drew an arrow to where I am talking about.

 

[jwaller]

I found an image provided in the link I was given above.

I drew an arrow to where I am talking about.

the brake light switch you have pointed to is in the MC bore and is wet with brake fluid. removing it will do no good for lubing anything.

 

[big block 88]

I'm not after lubing anything I need to know why the new hydra boost does NOT have this.

 

[hoop]

I have not seen one without the hydraulic brake switch opening. My guess is that yours is set up for the air brake switch. When I changed over to the air brake switch system I bought it from Dave at Eastern Surplus.

 

[rlwm211]

The picture in BigBlock's post #11 is of the new style airpack and you are correct that there is not a plug anywhere within the air system on that design.

No I would not remove the switch or any other plug.

I would consider lubing the air side of the air pack by doing as I described which is to squirt some oil in the air line AHEAD of the air pack.

I suspect that the new design airpack has no plug on the pressure side as a cost savings measure. The old style had a cast Aluminum cap and welded studs on the side of the big air cylinder; all of which costs money to produce. Cost saving measure and a redesign of the internals of the air pack allowed them to manufacture the design using stamped metal components and therefore at a savings. The actual slave assembly (Brake cylinder side) is still made out of cast steel and although is very similiar to the older design it is a bit different.

As to the wet brake light switch, if you can find the air switch upgrade it is a good investment as the BFS has been known to catch fire when the diaphragm in the pressure switch fails.. Although this is extremely rare, I have personally seen it happen.

RL

 

[runk]

I think you are referring to the "stoplight switch" as it's called in the TMs. Was originally in the hydraulic line, and at some point changed to putting it in the air line (I think the one that goes to the service brakes gladhand). A tee is swapped in for an elbow in the air line, as part of the MWO. I think the two types of switches are different (activate at different pressures, maybe different threads), but the electrical function and wiring is the same. Here is the page from the 2006 version of the TM that shows the air version.

 

[Floridianson]

Off topic but yes I feel oiling the airpack before the incomming valve is better. I was looking the outher day and looks like I might try one time remove the air tank pressure pop off at the tee and see if I can get a little down hill on the tee fitting. Then useing a squrt oil can pump some in there and I feel lke it will go in the down hill line and not get any in the air tank. Then we hit the incomming valve to.

 

[big block 88]

Thanks for all the help there fellas we got her all back together last weekend and she stops on a.... well not a dime but it will stop from 45 mph in a hurry dragging the rear tires along.

I never expected these trucks to nose down so much when heavy braking. But then again with all new parts on this truck we have never had one stop so well.

 

[Floridianson]

Thanks for all the help there fellas we got her all back together last weekend and she stops on a.... well not a dime but it will stop from 45 mph in a hurry dragging the rear tires along.

I never expected these trucks to nose down so much when heavy braking. But then again with all new parts on this truck we have never had one stop so well.

Did you do the major rear brake adjustment or just the minor or the top adjusters on the rear backing plate. This makes a big differance. You realy don't want the front to lock up and not the rear if anything it should be the rear that locks and the front slips just a bit.

 

[big block 88]

we did the upper adjustment on the rears, the rear tires locked up and drug along while the front continued to roll a bit it just nose dived more than I expected but the steering stayed true and straight it feels good to have great brakes on this thing.