Hey guys, hoping someone here can help. I've asked this on two 4900 specific facebook groups and no one has had a good answer. The part pictured is off a project truck I am working on. It's severely corroded. Every bolt broke trying to get it apart. The lower part is cracked. I got it apart and was expecting some connection between the upper electrical module and the lower valve. I see none. What is this and how does it work? The truck has ABS brakes. Air brake truck. I can't find a part number. Googling various things has lead me to similar parts but not an exact match. Does anyone have the part number for it? I never got to drive this truck and have no idea how much of the ABS system was working. The electrical module could still be ok. I would at very least need the lower part. Could I delete the ABS system from this truck? I assume the harness goes back to the ECM. Would it be possible to just put a basic relay valve in place of this all? I'll probably catch hell but I am not really concerned about ABS on this truck. I'll never drive it in the winter, and 90% of the trucks i've driven don't have ABS, so its not like I count on it.
Depends on year model if will pass DOT Inspect without the ABS Functional. WABCO style ABS, look that up on the Net as to the style of Modulator and the Control module. Likely need harnesses and more to get it to function right.
For one it says Bendix-and it's not Generation 4 or 5. Almost looks like a 6TAB but that's for trailer. Being a 1998 depending on month built it could be removed, ABS was required in mid 1998. I've seen several PacCar's that are 1998 without ABS.
I think this truck was built the latter half of 98'. I'd have to look. I was not aware the ABS system was inspected as part of the DOT inspection. Yes. The electronic part says Bendix on the top. I cannot find markings on the lower valve part. Those pics look like it. What did you google to find them?
This appears to be it https://s1partscenter.com/brands/international/brakes/valve/2501273c91 Is this just a relay valve for the parking brakes? Having nothing at all to do with the ABS system? The two Bendix modulator valves (Not pictured - Still in the truck) might be ok. They are not as ruined as this thing. Am I over complicating things here? I just made an offer on a set of service manuals on ebay. Have a feeling I am going to want them...
The pictures I put up are just random from Bendix's site. Truck Shop has lots of experience and just knows stuff
A dying breed... The truck was built in July of 97'. Not sure what that means as far as the possibility of an ABS delete.
You can gut it.
That will save me a a lot of money. Thanks
Make sure and remove everything, and I mean everything.
Cannot have a Warning Lamp show at all, and taped over does not work.
I am finally putting the brakes back together on this truck and I have a few questions I was hoping I could bounce off some of you. I am taking this from a semi tractor to a S/A dump. I don't believe I would have an inversion valve. I am guessing I will need to add one? Is this correct? I will need to get this inspected to get the registration changed. I am in Minnesota. I don't know exactly what they will look at. I have another truck without ABS. It appears to be plumbed like the diagram in this- https://n0c357rmy1njbuit2friqwu.blob.core.windows.net/documents/xMRZEnULI0EBhB_SD-03-4504_US_007.pdf R7 Modulating valve - quick release and relay valves. No inversion valve I can find so far. Truck is a 1998. Would I be kosher to just set it up the same?
I wouldn't worry, 1998 was a year of gray period for ABS. There were lots that were produced without ABS.
The DOT Brownshirts here have all but stated are getting to Component Obsolescence on the Pre 2000 and some Early 2000s, they are not certain if can force Upgrades to keep them functional if still road worthy or limited use machines.
I guess I am less concerned about the ABS delete and more looking for advice on what to order to set it up going from a tractor to a straight truck. Everything except the foot valve, Tractor protection valve and parking valves was in such bad shape I removed it and want to install all new. Does this diagram look correct for that - except with the ABS modulators removed? I don't have much experience with air brakes and the service manual for this truck really lacks a good clear layout diagram.
It's a basic diagram, but correct. The R-7 is a anti compounding valve displayed in that diagram. Yours may not even have a SR-1 or SR-7 all depended on what truck required to fit design. The foot valve you have will be dual circuit, one half for front and half for rear. The relay valve between the modulators should be a R12-green, the relay valve for park brakes QR1C quick release with a circuit controlled by the SR-7 for anti-compounding. Just plug delivery ports on tractor protection valve, remove modulators and reconnect. And you should be back to pre-abs. Make sure to remove all abs cables, either coil/tie up hidden or remove. By plugging TPV air will just deadhead/go no where, no need to change dash MP-3 valves unless leaking.
Thanks Truck Shop. You've helped me a lot on this project. I'll get some parts ordered this weekend. I'd like to get brakes back in this before winter. No, this truck never had the R1 or R7. I was trying to copy the Ford f800 I have. That has no ABS and has the R7. I was planning to keep the TPV and just use it for air to the rear for a tag trailer. You might get a laugh. I took the rear brakes all apart and cleaned everything up and looked it over. Didn't consider there is a right and left S cam. 50/50 shot and what do you know. got it wrong. Didn't notice until I went to put he slack adjusters back on. Was pissed because you have to take the hubs back off to swap them.
I know I can't mix brake chamber sizes on the same axle, but what would happen if I pit these larger cans on the front of the truck? Parts truck I got has basically brand new cans and slack adjusters. Was trying to utilize as much as possible. Slack adjusters off one of the rear axles are the same as the front, but the cans are larger. Assuming that would mess with the balance of brake application?
Factory designs balance brake application pressures, a type 16 chamber is 16 sq inches surface area a 24 is 24 inches, the values of force applied at 30-40psi increase by 50% increasing sq in by half. Does not appear a issue until emergency level braking and cannot steer due to locked and sliding tires.
That makes perfect sense. I'll order the correct cans. Thank you!
Is there a standard as to what these two lines typically do on a truck? The service manual is really useless as far as having a decent plumbing diagram for a pre ABS truck. Trying to trace them under the dash has proved difficult.