Chasing pressure issues

[Randomrunner12]

Hey all,

long story short, chasing a steering pressure issue with my truck. So is working it under warranty but it’s had 3 new gear boxes (2 redhead, 1oem 4 bolt) 2 power steering pumps one of which was a zf pump, 2 hydro boost pumps and new power steering hoses.

issue we are having is without truck rolling at least 4-5” either forward or back you cannot turn the wheel. Once all this was replaced we started getting a pulsing in the brake pedal when turning the wheel.

Numerous bleeding procedures done including the abs pump. Shop guys have been in contact with numerous other shops, Cummins master techs and such and we can’t seem to figure out what’s going on.

Any thoughts? also with the new power steering hoses can we pull the teflon liner or will that cause price issues? Truck is going on being in the shop for 3 weeks come Monday and would really like to get it fixed.

 

[Tuesdak]

I would jack up the front end and see if you can turn the wheels with the engine off. Something may be binding up.

Next thought is the return line from the hydrobooster. If it has ANY restriction including an in-line aftermarket filter it can keep the brakes on as the hydrobooster will not release.

Have they put pressure gauges on the PS system to see what it's doing? It's possible the relief valve and/or spring is incorrect from the pump replacements. (From a system without hydroboost.)

I only use NEW PS pumps as I have had lots of repainted garbage sold as rebuilt. One rebuilt POS lasted 30 min and blew a seal on the alignment rack ... after dusting the system from eating a bearing to the point the seal wasn't touching the shaft on one side anymore: I had to replace EVERYTHING, hydroboost, steering box, pump, hoses and flush the cooler.

 

[Ozymandias]

Why did you buy one of these inferior 4-bolt OEM boxes? What a waste of money that is.

For the problem itself I have absolutely no clue as you replaced the whole system top to bottom more then once.
Given that quality parts have been used im stumped here.

The only thing that comes to mind is - it is absolutely crucial for these pumps that the special tool is used to press the pulley on.
If it is just pressed on on the bench that kills the pump internals.

 

[Randomrunner12]

Why did you buy one of these inferior 4-bolt OEM boxes? What a waste of money that is.

For the problem itself I have absolutely no clue as you replaced the whole system top to bottom more then once.
Given that quality parts have been used im stumped here.

The only thing that comes to mind is - it is absolutely crucial for these pumps that the special tool is used to press the pulley on.
If it is just pressed on on the bench that kills the pump internals.

Only parts I’ve paid for was the first redhead box that went on during rebuild and a power steering pump that was a reman from AutoZone.

I have no idea if they are using a special tool or not to press the pulley on or using a bench press.

 

[Randomrunner12]

I would jack up the front end and see if you can turn the wheels with the engine off. Something may be binding up.

Next thought is the return line from the hydrobooster. If it has ANY restriction including an in-line aftermarket filter it can keep the brakes on as the hydrobooster will not release.

Have they put pressure gauges on the PS system to see what it's doing? It's possible the relief valve and/or spring is incorrect from the pump replacements. (From a system without hydroboost.)

I only use NEW PS pumps as I have had lots of repainted garbage sold as rebuilt. One rebuilt POS lasted 30 min and blew a seal on the alignment rack ... after dusting the system from eating a bearing to the point the seal wasn't touching the shaft on one side anymore: I had to replace EVERYTHING, hydroboost, steering box, pump, hoses and flush the cooler.

so no filter in the return line it’s a factory replacement set of lines.

I don’t know if they have put pressure gauges on or not but I’m leaning towards not. They keep saying they are getting a hydro boost but then again it’s only from local auto parts store so there is a chance they have been no good.

I’m going to call the shop Monday and talk with them to see if they are getting brand new parts or continuing with OEM.

SO far as originally stated, I’ve had 3 gear boxes, 3 power steering pumps, and 2 hydro boosts, I’ve also got brand new lines and I would freaking hope they flushed the cooler each time.

 

[Ozymandias]

I got a brand new ZF pump from Cardone that works flawless for the last couple years and a brand new OEM 6-bolt box that is stellar. Nothing rebuilt for me.

The only downside from this combination is that I can floor the brake pedal with a little effort, the new pump has a higher pressure then the old style.

 

[Randomrunner12]

I got a brand new ZF pump from Cardone that works flawless for the last couple years and a brand new OEM 6-bolt box that is stellar. Nothing rebuilt for me.

The only downside from this combination is that I can floor the brake pedal with a little effort, the new pump has a higher pressure then the old style.

When I call the shop Monday I’m going to talk to them and see what they have been installing and if they have decided to go brand new or not. I also told the shop owner either mopar 6 bolt or PSC but I don’t think that hasn’t happened since I haven’t had to pay any extra for any of this.

 

[Tuesdak]

What was the original problem you took it in for?

 

[Randomrunner12]

What was the original problem you took it in for?

originally went in death wobble, ended up having bad ball joints tie rods, front hubs and a weak gear box. So being a 20 year old truck that was barely ever driven I decided it was time to just upgrade the front end. Converted to the newer t style steering and bigger parts and after 2500 miles on the new parts, we’ve been chasing this hydraulic issue.

I even went as far as to put bearing blue clearance paint on most of the front end to see if there was any binding while turning or driving. Nothing. This can be confirmed as a hydraulic pressure issue but can’t seem to locate. Probably going to have to tell the shop to order all brand new parts and install and see if the problem goes away.

 

[Tuesdak]

I would suspect the wrong pressure relief valve and spring not making enough pressure. Possible PS pump bad. (Had several rebuilt repainted garbage not work out of the box.)

Next the hydro booster gets priority. So if the brake pedal is pulsing (assumed at a dead stop) the hydrobooster may have a problem including it's accumulator stuck trying to build up a reserve.

This all points to the PS pump and relief valve or hydrobooster. (The PS box gets fluid flow and pressure after the Hydrobooster.)

The next step is troubleshooting as the "parts cannon" isn't helping. This means they need a test kit to put a pressure gauge on the system to see what it's doing.

 

[sag2]

Fixed many of these when I was still working. If stock wheels (no excessive offset) it is a low pressure/volume problem. You need a quality pump that is for a diesel application. If it has offset wheels it is especially important to have quality pump.

 

[Randomrunner12]

Fixed many of these when I was still working. If stock wheels (no excessive offset) it is a low pressure/volume problem. You need a quality pump that is for a diesel application. If it has offset wheels it is especially important to have quality pump.

Factory rims. Tires are only one size larger but not enough to cause this problem. Waiting to talk to shop tomorrow to see what’s going on or where we are at with it.

 

[Randomrunner12]

Hey yall, any reason the teflon liner in the pws hoses can’t be removed?

 

[Ozymandias]

Hey yall, any reason the teflon liner in the pws hoses can’t be removed?

This is not your problem, leave it alone as long as it doesn't move by itself inside the hose.

 

[Randomrunner12]

Little update, shop pocketed the installed of a 6 bolt PSC box, it’s got a new power steering pump (for diesel) and hydro boost pump ( for diesel). Truck drove great for couple days, now randomly after a slightly harder brake , like getting cut off, or even braking at a stop sign and then again the pedal will drop all the way to the floor but the truck still stops fine.

one thing I did notice was that while going down a dirt road, as instructed by shop to assist with front end break in, I slammed the brakes when I got to 60mph and the ABS never kicked in or engaged!! I check the fuses for it. No issue.

truck is now at a different shop getting the brake system rear bleed and hopefully they will find something this other shop is missing.

anyone got any thoughts? Suggestions?

 

[Ozymandias]

Again, with the ZF pump you can floor the brake pedal. We figured that out here, everyone that upgraded the pump can now push the pedal to the floor with some effort. This is how it works.

Edit: doesn't mean drop to the floor - it has to be pushed to the floor. That's not the same.

 

[Randomrunner12]

I missed that part. So having a stiff brake pedal, and then having the pedal be able to lightly push to the floor before the brakes engage is normal?

 

[Ozymandias]

What do you mean with stiff pedal? Like with the engine off or so?
Can't push it?
And then all off a sudden it goes down like a brake pedal is supposed to work?

And also, I said it needs some effort to floor it, never said it goes lightly to the floor.

 

[Ozymandias]

Shop shall check for the ABS unit if it is internally leaking.
If they have no clue tell them to Google it for the Kelsey-Hayes ABS unit.
It's a pretty straight forward check to see if you need a new one or not.

 

[Randomrunner12]

Ozy I guess my confusion or what I’m saying I’m not saying right.

Drove truck after getting back from shop Thursday afternoon, put 80 miles on it l, drove great and perfect. Brake pedal was stiff and required maybe an 1”/1.5” of travel to get truck to come full stop at any speed. Which had been normal feeling since I bought it and did everything but the hydro boost. Drove it Friday to school and most of the mid afternoon.

Fast forward to Friday and this morning, when driving off I pressed the brakes more then normal, the next press would go to the floor (wouldn’t just drop) and truck would stop with pedal maybe 2” from full depressef, then the next use would be normal. I could easily duplicate.

I read a post sometimes abs valves can litter pressure by and by going in a gravel road and getting the ABS to kick on can fix the issue. even on gravel roads ABS should kick on when slamming brakes. Is this true? Cause I tried getting up to 60mph and then I slammed the pedal and abs never activated. Felt truck just skid with pulsing in the brake pedal.

i know that I’m asking allot but I literally have no clue what’s going on and am at a total loss. Unfortunately I’m working nights and school during the day borrowing my wife’s truck so truck has to go to shops as I have no time to do this myself until January when I graduate. I’m just trying to learn and understand what’s happening