cucv vac issues brake and trans issues

[wiccantoy]

ok ive looked in the search section and people are all over about this topic. my 85 k5 blazer has recently had what seems like a spongy brake issue and late shift issue in 3rd. im sorry if veterans to the forum are rolling there eyes about this but i just searched for a hour. please help

 

[wiccantoy]

just got back from my mechanic and i asked about a vac pump. he looked and said it doesnt have one, it has hydro boost for the brakes and electronics for the trans. now im lost

 

[Warthog]

You have two totally separate issues.

Sounds like your mechanic does know much about deisels or Military Vehicles. That being said, spend time reading the Tech Manuals so you will be able to work on it yourself or teach your mechanic. I'm not tring to be cute.

Almost every diesel vehicle will have some sort of vacuum pump. Either mechnaical of electrical.

The brakes do use the powersteering pump to assist the hydraboost brakes. Spongy brakes usually indicate air in the system. Bleed them.

There is a mechnical vaccum pump for the transmission. It is located at the rear of the engine where a distributor would be located. It will create around 20in of vaccum.

This vaccum is used to help the transmission shift. The Tech manual covers how to check it.

Here is a quick breakdown of how it works:
Pump creates vacuum, since diesel engines don't.
vaccum supplied to Vacuum Valve on injector pump
throttle position works the valve
partial vacuum is supplied to the tranmission vacuum modulator
vacuum modulator helps tell the tranny when to shift.

Any air leak in the system will effect the shift pattern

Section 3-21 of the TM 9-2320-289-20 Tech Manual covers the checking/replacement of the transmission vacumm hose replacement.

I even posted an thread on how to adjust the shift pattern

http://www.steelsoldiers.com/cucv/50568-cucv-throttle-vacuum-valve-adjustment.html?highlight=vacuum

-----------------------------------------

Not just for you but everyone that owns or is thinking about owning a Military Vehicle:


The Government spent a lot of time and money creating the Tech Manuals. They are way better that any Haynes or Chilton manual can ever be.

Almost every possible issue is covered in them.

 

[wiccantoy]

ok warthog there is vac on one port but no the one going tword the trans. would this indicate the valve is bad?

 

[Barrman]

When you go to bleed the brakes, if you find evidence of a leak. Which you probably will if air is getting in. Just buy new calipers. I put a new pair on my 1009 yesterday. $12.00 each at Oreilly's. I did one and my 11 year old Colton did the other. Took longer to jack it up and remove the tire than it did to swap out the calipers. Bleeding took no effort or time either.

I had one seeping fluid and brakes a little spongy. I let Colton drive the truck out of the shop and he tapped the brakes to test them. He honked the horn with his chest they work so much better. My wife didn't care to see him look like a crash test dummy though. Even though he was only going 5 mph at the most.

Follow the directions in the -20 manual for changing out the brakes if you don't know how. You will need a 3/8" hex wrench. Better to get a 3/8" hex socket, but you can get by with just the bent metal version.

 

[wiccantoy]

are they the same as the normal k5's brakes?

When you go to bleed the brakes, if you find evidence of a leak. Which you probably will if air is getting in. Just buy new calipers. I put a new pair on my 1009 yesterday. $12.00 each at Oreilly's. I did one and my 11 year old Colton did the other. Took longer to jack it up and remove the tire than it did to swap out the calipers. Bleeding took no effort or time either.

I had one seeping fluid and brakes a little spongy. I let Colton drive the truck out of the shop and he tapped the brakes to test them. He honked the horn with his chest they work so much better. My wife didn't care to see him look like a crash test dummy though. Even though he was only going 5 mph at the most.

Follow the directions in the -20 manual for changing out the brakes if you don't know how. You will need a 3/8" hex wrench. Better to get a 3/8" hex socket, but you can get by with just the bent metal version.

 

[wiccantoy]

ok anyone know where i can get a replacemrnt part (valve) the one on the side of the ip? ive called advanced, napa , and western auto ?

 

[Barrman]

I bought '85 K5 Blazer calipers and what I took off was exactly the same in size, shape, fittings and pad mounts. If they aren't the same, I don't know what the difference would be. Yes, I used '85 K5 Blazer parts.

 

[Warthog]

ok anyone know where i can get a replacemrnt part (valve) the one on the side of the ip? ive called advanced, napa , and western auto ?

You will not find it at the usual parts houses. I have seen them at some of the Military Supply Houses and they run ~$90. Are you sure yours is bad?

From the TM 9-2320-289-20p parts manual Figure 10 , Item #10 the GM part number is 14057219. Sometimes you can find them at the dealership or online.

 

[Barrman]

Joe, we do this tag team thing pretty good.

 

[Warthog]

Yes we do. I'm just trying to catch up with you on the number of posts...LOL

 

[wiccantoy]

ok have replaced the cracked vacume line and turned the vac valve slightly tword the fire wall. and the truck still shift from 1st to 2nd at 30mph. Any more info that can be given for the help of this issue? I have the part # from gm with the proper name for it but gm wants 130 bucks for it.

 

[niferous]

I had a problem very similar to yours recently.

http://www.steelsoldiers.com/cucv/45198-hard-shifting-still-after-repairs.html

To sum it up though my problem was the rubber line that goes from the metal line leading to the trans modulator underneath the truck. I had at first looked at and inspected by touch the line. Only after actually removing it did I find the leak. I would replace that and see if it helps.

 

[wiccantoy]

thank you very much for the reply will do that tommorow.

 

[wiccantoy]

ok since i have no patience i checked and the hose is good on the valve to trans gonna get the valve first since its the cheap one

 

[wiccantoy]

well looks like since the trans valve is cheaper im replacing it and yes it is the adjustable one from napa a whole 11. bucks. im also going to replace the metal vac line with a new rubber one from ip. to trans. hopefully tommorow ill have more info for all

 

[niferous]

More than likely its not the metal line.

 

[wiccantoy]

Well im not taking any chances. ive seen threads that there was cracks in the metal line. just useing the chance to get rid of any options for problems

 

[niferous]

If you have an air compressor you can blow air through it and check for leaks that way with the engine off. With the truck running were you getting any vacuum down at the metal lines outlet where that little hose goes to the trans modulator?

Another question is when you move the trans modulator valve on the side of the IP does it have spring tension?

 

[wiccantoy]

ok all is fixed now. replaced the vac line since it looked like it had a split in it. also the trans shift solenoid on the trans with one from napa that is adjustable. all seems to shift nice and smooth at low rpm's now. now i need to locate a used class 3 hitch for my stump grinder and find the time to reweld the 2 holes in the floor. THANK YOU ALL FOR THE HELP