1994 GMC Safari ABS Brake Pressure Modulator module

Joined
Aug 3, 2007
Messages
829
Likes
0
Points
16
#1
I put new brake lines on this 1994 GMC Safari all the way from the ABS module to rear and front brakes. Very hard to get to and work on. Anyway since I disconnected the lines from the ABS module, I want to know if I have to bleed the ABS module after installing these new lines. I know that I have to bleed the Master cylinder and the rear combination valve first before I bleed the ABS module of which I will do. If I manually bleed the ABS module I know I need some special tools for the "High Pressure Accumulator Bleed Valves" of which I don't have. I have a Old Snap On mt2500 with a mt25001099 domestic combination module in it and don't know if this will engage the ABS module to turn on and off so to blled them without the special tools.

On the same subject of the ABS module, could you tell me in what position the little shaft or pin should the two "High Pressure Accumulator Bleed Valve" be in. I was checking to see how hard it was to even get to the bleed valve and found out that the little shaft on the bleed valve on the right was out and the one on the left was in. I took a little light soft instrument and tap the one on the right in to match the other. Is my ABS module Bad? Thanks for any advice and help.
 

brcidd

Hero Member
Joined
Nov 16, 2006
Messages
272
Likes
1
Points
18
#2
My '94 astro is now just like a '92, that had no ABS...not worth fixing IMO. because of the special tools and expense--I have driven it another 160,000 without module plugged in....
 

jjm

Hero Member
Joined
Dec 1, 2006
Messages
349
Likes
0
Points
0
Location
NYC
#3
I think the brick can bleed the BPMV, not sure of the config though, but no special tools needed. If not, you can bleed manually, but you'll need 3 of those proportioning valve depressors to bleed the BPMV.

Remember replacing a master cylinder on of these these, and just left the ignition on and bled at all the wheels (seemed to be impossible to bleed with the ignition off. Seemed to be fine, but maybe I just got lucky. One thing was the ABS light needed to be cleared afterwards, no biggie. Not saying you should do this, and might not work if the system is really air bound.

Joe

If you found this information helpful, please support BATAuto!

 
Joined
Aug 28, 2007
Messages
4,853
Likes
26
Points
48
#4
I got so damned paranoid after that idiot kid hit me, his damned insurance company hired a bunch of experts to examine my vehicle for any modifications so they wouldn't have to pay the claim. Bastards even lied, but they weren't dealing with a complete idiot, threatened to sue them, and they backed off. Also have a lot of experience as an expert witness. Since its clear my DeVille has ABS, it had to work, if wasn't worth fixing, would have pitched the car. Another thing you learn about insurance companies dealing with accidents on a continuing basis, tie up the best law firms. Found a good attorney 150 miles away, he didn't cross examine me, I crossed examined him.

I do not recommend disabling your ABS, even though it a pile of BS. Says if it defaults, doesn't interfere with normal braking action. What a big pile of BS that statement is! You can clearly see two lines from your master cylinder going into the ABS with four lines going out of it. And it has valves that can completely block fluid flow to any or all of your wheels.

Also read some study that ABS had an 8% effectiveness in preventing an accident, just enough so all new vehicles are required to have ABS. You can't fight city hall on this issue, and your senator and congressman are complete idiots on this subject as well as a thousand others these 1,525 government agencies formed in the last 40 years come up with. Bastards are just trying to protect their jobs. And doesn't help that about 98% of the American driving public doesn't know a damn thing about their vehicles. What do you do for a living? Design electrical charging and ignition systems for cars. What is a charging and an ignition system? Do I have one of those in my car?

Really not ranting, but this is just as important as turning a wrench the way this country has become.

On this car learned you needed a GMTech I scanner with an ABS module, thought they would be giving these things away for nothing on ebay, no luck, but all it does is electronically turn on the ABS pump. Found the connector and used a 14.5 V power supply to run it, draws 5 amps. Powered it, started off with the LR, cracked opened the bleeder and bubbles flew out like crazy. Vacuum pump did not work, could pump all day. Also learned with the bleeder barely cracked open, ignition off, would activate that solenoid, just for a second. That is the only way I could get a full pedal. That also worked on another OBD I vehicle GM SUV. That one actually showed codes by jumping pins on the diagnostic plug, but nothing to switch on the ABS pump. Really don't know if you try, GM sourced out ABS modules to a bunch of different people.

Shop manual has 69 pages on the ABS on this car. How can anyone write 69 pages and not say a damn thing? But they did it.
 
Joined
Aug 3, 2007
Messages
829
Likes
0
Points
16
#5
I have been researching this Kelsey-Hayes 4wal system. No way around it that I saw as far as using the J-39177 tool to depress the High Presure Accumulator bleed valves when you manually bleed the system. . Unless you want to take your life in your hands and go out with just the front brakes around 4mph and slam on the brakes to actuate the BPMV so as to bleed itself and then come back and bleed the wheel cylinders. (Not for me!!). I am going to hook up the brick and see if this version can activate the self test on the ABS. The module says it is Bydirectional. I bought this piece of Junk from my sister in law because she had money problems and wanted me to lend her money to pay her bills. I did this twice already and she had money coming in to pay me back, of which she did. This time she had no way of paying me back, so I told her that she could sell me that old gmc van. I did not need another vechicle!! The last time I seen it, the van was fairly decent. I bought it sight unseen because I just wanted to help her out someway. Bib Big mistake. I have never in my life worked on a vehicle that had so many thing wrong with it. I would have been better off taking it to the junk yard and cutting my losses. I have too much in it now to turn back! I couldn't begin to get half the money back that I have put into it. When I get it fixed, and use it for a work/hauling van, the next stop will be the junk yard. HA HA
 
Joined
Aug 28, 2007
Messages
4,853
Likes
26
Points
48
#6
Very familiar with money problems, with six brothers and sisters, old man left the country when I was ten years old. Only way I could get a car was with my paper route money, what little my mom would let me have. Purchased old wrecks and learned how to fix the. When I was 14, was tall enough to reach the pedals, and thought myself how to drive in the middle of the night. Ha, swiped license plates from my wrecking yard, but took those off after my nightly runs when my mom was asleep. Clocked in over 12,000 miles before I was old enough to get a license. Never got caught, LOL.

Was doing pretty good until my company moved to China four years ago, half of my SS checks are paying my property taxes, could sure use that money. So I am right back where I started in life, fixing old wrecks.

Well, I do have a good sized bank account, but took a long time to build that up, buying a new piece of crap could put a large dent it that. How old are you anyway? I am 72.
 

jjm

Hero Member
Joined
Dec 1, 2006
Messages
349
Likes
0
Points
0
Location
NYC
#7
I thought you were referring to the Snap-On MT-2500 as the piece of junk, then I realized your were referring to the truck... whew!

It's sad but true about people not knowing anything about cars these days, but they sure think they do, and have all the answers about the kind of hybrid and electric vehicles we should drive. It always amazed me about the whole Toyota sudden acceleration issue. In my parents day, if that happened because a throttle spring broke or a motor mount gave way, they would know enough to slip their foot under the gas pedal, downshift or shift in neutral, brake, and/or just turn the ignition off. Today, they just panic and get on their cell phones as the speedometer starts going into triple digits. But they're positive in their knowledge that we should be driving "green" vehicles, because they know everything there is to know about cars.

When I was growing up, it was quite common to see the men in the neighborhood under the hood, and I couldn't get enough of it! It was great going from car to car, seeing different types of jobs... and learning a bunch of different curse words! I'm sure I got in the way, but I was always eager to learn and help. Today, most men don't work on their cars, or anything else for that matter, but they sure know how to work their smart phones.

It always annoys me when I see car ads in the sports section of the newspaper when most men don't have a friggen clue about cars! I thought it was pathetic how I guy I work with had to call AAA to change a flat tire. But in his defense, it was raining outside at the time, and wouldn't want him to melt. I'm also amazed at how many women take the lead in dealing with contractors on home improvement projects, and even tackle projects themselves, while the men lounge on the couch and watch sports and play video games.

Welcome to modern America! What is happening to this once great country?

Joe

If you found this information helpful, please support BATAuto!

 
Joined
Aug 3, 2007
Messages
829
Likes
0
Points
16
#8
Well I found out the my snap on scanner will not activate ABS brake system for a OBD1 system on this particular GMC van. It will only give information to the status of the system and tell you if you have any problems, but that is about it. Have to make tools to depress the high pressure accumulator bleed valves, because I don't think I want to pay $20 each or so dollars for three dispressors. Man those bleed ports and internal bleed ports are hard to get to. Don't even know if I can reach them with my short arms.

NickD: I came from a family of 10 myself. Also had a paper route and caddied since I was 12 to sixteen years old. . Make a whole $10 a week. First car was a 1947 Plymouth with a rod knock at age 16. Had to buy it myself. Mom and Dad were too poor to buy me on or even help out. Took the oil pan off and filed down the rod cap and checked it with gauge paper. Those rods in those days had babbit bearing instead of inserts on the Plymouth. Drove that car for another years and sold it for more than I paid for it. My birthday was June1 and I got my permanent license on June 2 of the same year. The man asked me where I learned to drive. I said, " nowhere. I just learn fast". LOL I wasn't kidding no one!! I been driving off and on for a couple years at that time. I am a broken down 71 year old man. Been working on cars even before I was sixteen. We would soup up our car and take them down to the dragstrip and race them. Never did win though.
 
Joined
Aug 3, 2007
Messages
829
Likes
0
Points
16
#9
Well I could not bleed the rear brakes because the combination valve that shut off the front or rear depending which line breaks wasn't centered and cutting off the supply of fluid to the rear brakes. Got the front brakes bleed first so I could at least drive it out of the garage. I finally got it centered and will bleed the entire system again tomorrow. I know I got good front brakes anyway. Before I got the combination valve centered, I got at the end of my driveway and run down it heading toward the back yard and steped on them hard trying to activate the abs controller, and have a skid patch from the front wheels about 8 foot long, straight and true. I don't know if it worked or not to activate the controller. Will find out sooner or later.

JJm: The mt2500 scanner is a good scanner for me. Just got to learn how to use it more effectively. As far as the GMC van goes, one of these days I will have a Mechanically Sound Van. It would not be the first vechicle that I have rescued from the thrashing machine. My family drives them till the very end. It's hell to be the families mechanic!! LOL
 
Joined
Aug 28, 2007
Messages
4,853
Likes
26
Points
48
#10
Peers in high school rode me constantly for driving a 37 Cadillac Limo, I thought it was cool, but the pressure got too great so got rid of it. Found a nice clean 48 Plymouth coupe for 40 bucks, but also with a rod knock. Not sure where you came up with babbitt bearings, those were dropped in the early mid 30's in favor of inserts.

Neighbor was a Chrysler mechanic and always was bringing cars home to rebuild for a few extra bucks, also was my adopted dad, was a German, and a perfectionist. He got me a 2 mil undersized insert, handed me his micrometer, a piece of emery paper, oil, and told me to sand the crankshaft journal down. It has a flat side so had to take the rest of down until it was perfectly round. This required constantly to hand rotate the crank.

Got the brilliant but stupid idea of just nudging the starter to do that. Darn thing popped the instant I hit the key and through that loose rod through the block. All wasn't lost, he found me a 54 Dodge pickup engine with only 12K on at a wrecking yard. Got the complete engine with everything on it and a nice silver paint job for 65 bucks. Was a larger engine, but fit perfectly. Then I had a decent car.

I still nudge the starter when working, but use a remote starter and disable the ignition first. With peer pressure, go to hell, I will drive whatever I feel like driving. At 15, know more about cars than my auto shop teacher, he had no idea how to rebuild a four barrel Rochester. First job at 18 was as an auto mechanic, but Uncle Sam had different ideas. From there went on to college and became an engineer. Even wore blue jeans to work so I could get my hands dirty with engineering problems, after all, that is where the problems to be solved were.

Scanner just energizes the ABS pump taking the silly-con diode route, so I just hot wired the pump. With the rear brakes, barely got a drip, even with the vacuum method. With the pump running, opened the bleeder and within seconds poured out a bunch of bubbles then became clear. Took all but about five seconds to get clear fluid.
 
Joined
Aug 3, 2007
Messages
829
Likes
0
Points
16
#11
NickD: I had to do some research on babbitt bearings on my 47 Plymouth, because I know the bearings had something to do with Babbitt. This was a long time ago and I was 16 years old and just starting to learn a little about cars. Any time that I needed mechanical advice, I would go down to the local gas station that had a good mechanic that liked me and he would help me out with my mechanical issues. He would even let me use his car lift. I learned that the 47 Plymouth and other cars in that year and even later years used "steel backed babbitt bearings inserts". I guess some of the cars had steel backed with bronze etc. I guess what I did was file down the cap and also a little on the insert also. Also cleaned up the crank. Heck, that was 55 years ago. Sometime I barely remember what I did yesterday! LOL
 
Joined
Mar 1, 2002
Messages
3,665
Likes
63
Points
48
Location
Kentucky
#12
I am just a young pup of 53, but I can remember filing the bearing insert ends, but also selecting brass shim stock of the proper thickness, then cutting out a shim by hand and putting it under the bearing insert. Always a test of skill to allow space for the little tooth that keeps the insert from spinning.
 
Joined
Aug 28, 2007
Messages
4,853
Likes
26
Points
48
#13
Those were quick fix em uppers to dump a car for a couple of bucks more. Got a 54 Olds Holiday 88, pulled the engine and only kept the heads, block, cam and crank, intake, and exhaust manifolds. Had the cylinders bored out 60 mils over, crank ground, and replaced everything else with brand new, water pump, oil and fuel pump, etc., for under a hundred bucks. Today, a hundred bucks is only a down payment on an overhaul gasket set.

Back then even a really super clean car very well maintained, that turned the clock, for the younger guys, that meant going over 99,999.9 miles, the car was considered worthess, could pick one up for 50 bucks or less. Add a hundred bucks, and really not that much work back then, have a brand new engine.

We lived out in the sticks, was 1 1/2 miles to town, one job I had every day during the winter months for two years was to carry a five gallon can to the gas station for fuel oil for our space heater when I was 13-15 years old. Wasn't bad walking to the station, but hauling back a 40 pound can wasn't easy for that mile and half. Mom never had a car, never even knew how to drive. So it was walking everywhere. Could only dream about having a car, found a 30 Olds on my paper route for ten bucks that didn't run. Took me hours to convince her to let me buy it, she had to sign for it, so I could learn about cars. She never knew I got it running and was sneaking out at nights, well, I did tell her about ten years later.

Always have been a nut on transportation, cars, trucks, motorhomes, boats, planes, and motorcycles, but no more motorcycles, you can get killed on those things, almost did with the nuts on the road today. Oh, not to mention farm tractors, push and riding lawn motors, chain saws, blowers, snowmobiles, ATV's, snow thowers, and model airplane engines.
 
Joined
Aug 3, 2007
Messages
829
Likes
0
Points
16
#14
I was so much fun remembering the old days I almost forgot what the original question was. Lol Anyway I got the brakes fixed. I manually bled all the wheels and it seems to be a good strong big pedal. I guess when I finally took my life in my own hands when I run down my driveway towards the back yard and slammed on the brakes, it must have activated the ABS controller so as to bleed the controller. My wife said it was too hot for her to help bleed the brakes so I did it by myself by opening the bleed screw on the right rear a tad and put a hose on it and down into a glass jar submerged in some brake fluid. I put a voltmeter on the combination valve switch and watched the volts (o volts),so as not to overstroke the pedal and push the centering valve back to one side and close off my rear brakes again. If it went to 12 volts I knew I screwed it up. The jar filled up with some nasty fluid and I went over to the other side and did the same thing. A mans gotta do what a man gotta do!!
While replacing the brakes lines I noticed that the piece of vacuum hose that connected the Vapor line coming from the tank to the vapor cannister was rotten. I replaced it with a new good piece. About 6 inch piece. I think that might have had something to do with a bad idle because when I started it up and idled it, the idle seemed a lot better. Before I could just step on the brakes while idling and the idle would get worse. It didn't even effect the idle now when I pressed on the brakes.
I think I may need to get rebuilt injectors or find a way to clean these out because I have a spray pattern but I can see it dribbling a little when it is running. I know that isn't right and I will have to fix that before I get the best idle possible. I put new spark plugs in and checked the compression and all six cylinders had about 176 # of pressure with the throttle open. I can see a new set of wires coming in the future. Thanks everybody for the input and remembering the old times with me.
 

nickb2

Wrench. Diagnostic Tech.
Joined
Nov 22, 2008
Messages
10,556
Likes
185
Points
63
Location
St-Hyacinthe, Quebec, Canada
#15
Damn you old men. I am thirty six and seeing you all rant off about this and that makes me not want to grow old!! ???

Jokes aside, the snap on brick or the mac tool mentor or the otc genesys can and will do all abs modulator bleeding. They even come with OBD 1 connectors by the way. I don't see a problem if you have access to these awesome scan tools. If not you can always go drive the truck hard until abs actuates and shudders your brake pedal. Then go back to your shop and bleed the rest. Just be careful to drive insanely in deserted streets.

If after bleeding the AWD module with a proper scan tool and you still have a hydraulic problem, look back to see if the hoses and fittings are secure and tight.