CAT IT28B Loader *No Brakes*

Hey guys,

I have an issue with my 87' CAT IT28B, it has no brakes! It has an air over hydraulic system. I replaced an air line that had a hole in it, tested it out and no brakes. Compressor is working fine because the system keeps released air from the relief valve located on the air tank every 30 secs or so when at idle.

I press the brake pedal and I can feel some air pressure there and it makes an air sound. But no brakes what so ever.

Both master cylinders has fluid in them also.

Any tips would be appreciated!

serial number please.
are you saying that air comes out of the safety valve on the bottom of the air tank on a regular basis .if so you have a faulty relief valve or the governor is not unloading correctly
no air should come out that valve unless some thing is wrong. the system air pressure should be somewhere around 95psi
Mark

Serial # 1HF00566

Yes air is coming out of the safety valve on bottom of the air tank. I did order a new relief valve earlier, so I'm hoping thats all that it is and its not building up enough pressure to activate the brakes. It that doesn't work, I'll resort to the governor as you stated. Thanks Mark! I'll let you know in about a week when I get that part in and installed.

If the safety valve is releasing there is plenty of air pressure. Split the master from the air actuator and see what's happening when the brake pedal is depressed. Also see that the piston in the master cylinder isn't stuck at bottom of the bore.
Governor most likely cause of safety valve blowing off

Almost guaranteed that your master cylinders will be rusted up in the air side.

1. Take them off,
2. Strip and inspect.
3. Try to hone the rust out.
4. Buy seal kit.
5. Reassemble.
6. Find they now leak air.
7. Take them off again.
8. Install new ones.

(Steps 2 thru 7 are optional.)

bgilliscat said:

Serial # 1HF00566

Yes air is coming out of the safety valve on bottom of the air tank. I did order a new relief valve earlier, so I'm hoping thats all that it is and its not building up enough pressure to activate the brakes. It that doesn't work, I'll resort to the governor as you stated. Thanks Mark! I'll let you know in about a week when I get that part in and installed.

Click to expand...

Did this thing ever have working brakes while you owned it?

Where in Ma are you that it takes a week or more to get a safety relief valve? Also if it is building up any pressure the brakes should work at least some. Even 30 psi air pressure would give you some brake action.

Does this machine not have an air pressure gauge of some kind? Without looking it up in SIS I can't say what it has but there must be at the least a warning light that would come on if pressure was too low, say under 60 psi. I would assume this has a parking brake that should come on with too low an air pressure, does that work?

I can only hope you are not trying to operate this machine with no brakes or someone is going to get killed!

The brakes have not worked since I have owned it, although by looking at the rotors they have a nice shine and appears that they were recently working prior to purchase. If they were all rusted up I would say the brakes may be locked up. I'm also not operating it, its pretty much a project machine until I get some odds and ends fixed on it. I have no gauges or warning lights since electrical work is a few of the things to repair.

I installed the a new relief valve tonight, the machine no longer purges air out of it every 30 seconds or so. Its quiet on that end with the exception of the engine noise. BUT the brakes are still not working. When I step on the right brake pedal I get just get a quick sound of air, the pedal feels good with plenty of air pressure against it. But not even the slightest slowdown of the machine when I step on the brake pedal to stop it.

I'll investigate the master cylinder as some of you have stated, thanks for you help!

check to see if the master cylinder stroke indicator is extended, it is part of the mechanism that operates the switch for the brake indicator .if it is extended try and push it back in, if it goes in may just need bleeding, if it wont go back in that would indicate the piston is seized in the full stoke position and as others have said probably rusted up.
Mark