Huge hesitation, mechanically inclined. Please help

[Brian Wilson]

Pulled the fuse as a test first thing this morning. Everything seems great. Not sure how long it will last. I'm going to run it a few days and then put the fuse back and see if the problem returns.

 

[Brian Wilson]

Could my use of valvoline synthetic dot 3- dot 4 brake fluid have caused this? Someone said it could. Not sure if it is accurate but I'm a all synthetic fluid guy. Never had a problem before.

 

[Rocket Man]

I'm not sure but that sounds like you should definitely look into it further. Im strict about using recommended brake fluid. Too many horror stories about ruined brake components from using wrong fluids or failure to get all the old fluid out and ending up with a mixture.

 

[Chip18]

The Dot 4 "should be fine" but I'll let someone else answer that one. Take a closer look at the harnesses on all the wheels for the "ABS" sensor wires?? I'm "assuming" these have them??

On my 951 the "ABS" would go off and the dashboard would light up like a X-MAS tree whenever I hit a bump most disconcerting?? You have to shut the car off and restart to rest it ... it was other wise fine so ...whatever.

While working on other issues ... I noticed the wheel harness for the ABS system?? I also noticed that both sides did not look the same?? It's a 89 944 Turbo S and "somewhere" along the line some A-Hole decided ... to hack up the harness on the driver side??? The grounds were missing on that side?? Don't know if these vehicles have a similar ABS Harness setup ... just a thought.

But ... another idea ....

https://www.google.com/search?q=inf...=chrome..69i57j69i61&sourceid=chrome&ie=UTF-8

Maybe one of the brakes ... is dragging??? One of those is a way to find out ... I should get one myself.

 

[Chip18]

I'm not sure but that sounds like you should definitely look into it further. Im strict about using recommended brake fluid. Too many horror stories about ruined brake components from using wrong fluids or failure to get all the old fluid out and ending up with a mixture.

Yeah ... I'll go with this. PT Cruiser ATF 4 ... only!

 

[Brian Wilson]

Is a mixture a bad thing? I always try to flush out completely but it's hard with brakes by yourself

 

[LADenali]

If you've done the following:

1. Booster: You'd experience longer braking times, plus this is only in effect when you brake.
2. Master Cylinder: When replacing, did you bleed on the bench prior to install? Sometimes air gets trapped and is not properly bled off.
3. Front Calipers: They seem to be reacting fine if your experiencing pressure.

I'd say the proportioning valve is the culprit. I tried looking up the GM parts list but cant seem to locate it. Not sure if its folded into the ABS system.

 

[Chip18]

Is a mixture a bad thing? I always try to flush out completely but it's hard with brakes by yourself

Just to this ... :

https://www.motiveproducts.com/products/0118-bleeder-race-pack

Freaking "Porsche" (944's) are a bleeding nightmare to bleed without one!!

 

[Chip18]

If you've done the following:

1. Booster: You'd experience longer braking times, plus this is only in effect when you brake.
2. Master Cylinder: When replacing, did you bleed on the bench prior to install? Sometimes air gets trapped and is not properly bled off.
3. Front Calipers: They seem to be reacting fine if your experiencing pressure.

I'd say the proportioning valve is the culprit. I tried looking up the GM parts list but cant seem to locate it. Not sure if its folded into the ABS system.

Aww "portioning Valve!!" It's gotta be in there somewhere??? Hey did a search ... it looks like it's not buried at all.:

https://www.google.com/search?q=gmc...5qvPAhWDRyYKHbOtAyIQ_AUICSgC&biw=1093&bih=541

But the infrared thing to read brake temps to see if there is a problem with an individual wheel, would be a good idea before screwing around with that system!!

 

[Brian Wilson]

It's definitely both front brakes. And pulling the abs fuse helped for about a day. Problem came back. Going to see if there is a proportion valve between the abs assembly and the front calipers.

 

[02Lightning]

You aren't running different size tires from front to back, or something crazy like that are you? Maybe causing the ABS to kick on and pull timing? You mentioned earlier that the timing was all over the place, so that had me thinking bad cam phaser.

@ Chip18, no lighting any more, traded it off for a CTS-V. It was a kick ass truck.

 

[Brian Wilson]

I assume the timing was way retarded because of the brakes dragging at this point. It must have thought it was pulling a huge trailer. But I'm running factory height and tires.

 

[Brian Wilson]

Since I know I didn't do a great job bleeding it I'm buying the suggested pressure bleeder and about 6 bottles of dot 3 (gm suggested) and bleeding it right with computer cycling abs motor. Hope this solves my issue. On a side note, my v2 by blackbear should be here wednesday. Excited for that

 

[Chip18]

You aren't running different size tires from front to back, or something crazy like that are you? Maybe causing the ABS to kick on and pull timing? You mentioned earlier that the timing was all over the place, so that had me thinking bad cam phaser.

@ Chip18, no lighting any more, traded it off for a CTS-V. It was a kick ass truck.

LOL ... well CTS-V. well a CTS-V ... is pretty cool but ... being able to do a 100 + mph on the Autobahn while hauling a Kitchen Aid refrigerator ... priceless!

 

[Rocket Man]

Since I know I didn't do a great job bleeding it I'm buying the suggested pressure bleeder and about 6 bottles of dot 3 (gm suggested) and bleeding it right with computer cycling abs motor. Hope this solves my issue. On a side note, my v2 by blackbear should be here wednesday. Excited for that

You should be able to buy a gallon to start with, I did last month when I did a GMT900 front brake upgrade and stainless steel hoses for all 4 wheels.

 

[Chip18]

It's definitely both front brakes. And pulling the abs fuse helped for about a day. Problem came back. Going to see if there is a proportion valve between the abs assembly and the front calipers.

What??? The front brakes are dragging??? How do you know it's "both" front brakes???

In anycase ... your making progress. If it's both front brakes?? Then it would/should be something in common??? Air ... trapped in the abs pump or yeah the proportioning valve?? Or "possibly" both brake lines failing ... ie soft and spongy???

Now ... would be a good time to upgrade to Stainless Steel Brakes Lines! SS brake lines are not necessary ... but inasmuch as your going to ... "bleed the brakes" yet again ... might as well.

If you have to bleed it "once again ...sigh" it would behoove you to get the "Motive Power Bleeder." And while I can no longer find the site?? I did read that "Air Trapped" in the "ABS" pump can be a real bear to get out!! Lost that site so ...yeah.

At anyrate ... a tip from "Porsche land" ... when bleeding the brakes ... you want the front of the vehicle lower than the rear to help force air bubbles out of the "ABS Pump."

 

[Brian Wilson]

Nice tip. I bought a pressure bleeder for gm master cylinders specifically since I have a few of them. Holds 2 gallons of fluid. Presurizes the MC and keeps it full. Going to attempt it this weekend. Hopefully it works. Vacume bleeding g sure didn't. On a side note, my fluid was pretty black. And when I changed the caliper on passenger front I vaccume bleed. It started dragging. When I changed both front calipers, I did the old 2 man bleed pumping the pedal while a computer cycled the abs and changed the master cylinder. Now they both drag. I am absolutely 100% sure it's nothing to do with the rubber lines or the pads or the calipers themselves. So, it (probably) has to be air in system, I'm just not sure how air could cause it. I know air compresses more than fluid so it makes the pedal sponge like. But in my past experiance, it can't make a brake lock up.

 

[Brian Wilson]

Maybe the master cylinder closes and then the air expands alittle pushing the caliper piston out just enough to drag and builds heat that transfers to the fluid causing it to expand and push the caliper out more causing more drag and heat? Am I thinking too much on this?

 

[Brian Wilson]

I'm sorry I always write the longest posts. I just like to be informative.

 

[Brian Wilson]

I see I killed this thread. Autocal just found a code. P0325. Going to see what it is tomorrow. 14 hour shifts are killing my productivity