Weird issue with brake pedal feel and PS pump

[IBMobile]

You could add a transmission filter in the power steering return line.  This would help keep contaminants from reaching the hydroboost and steering box.

 

 

 

[Dmaney]

On 8/9/2018 at 9:57 PM, Mopar1973Man said:

As long as I keep changing my power steering fluid I hope that I don't have to do that job for a long time yet. 351k and rolling...

Wish I had been fortunate enough to own my truck since new like you. I bought it with 98k on it and flushed power steering system shortly after, it was nasty black to say the least. I did put a power steering filter in as per @IBMobile in hopes to catch any remaining floaters in the system. Plan on another flush this fall just to see how it looks and c/o filter. 

[Mopar1973Man]

The bad part is that the sludge will be high in the gearbox and most likely require a full disassmebly to remove the sludge from the gearbox. This is why you need to keep up on the fluid flushing and not worry much about the filtering. Just like engine oil if you leave it too long it will sludge up the engine. The only way to clean the engine up is fully disassembly. Oil filters still won't remove the sludge.

[Dmaney]

10-4. I will report findings when I flush it again. And post pics of fluid from both flushes. It probably has 7,000 miles on it since flush. I wrote mileage down, I double check. 

[KATOOM]

Haggar, have you rebuilt one of these hydroboost units???

[Haggar]

K,

 

Yes.  It is not hard.  Send me a pm. I can help walk you through it.

 

Hag

[KATOOM]

OK just to confirm something before I go tearing things apart...  Last night while noting disassembly procedure I pressed on the brake pedal with my hand, and the pedal acted like a sticky syringe plunger or like a shaft seal skip / jump a little while moving through a bore.  But this happens ONLY during the initial movement, and not through the full stroke.

 

Everything I read says a stutter or shudder of the pedal means low fluid.  I just want to be sure I'm not taking something apart that doesnt need it...

 

While using forums, sadly its amazing how many people post their issues with the hydroboost but never bothered to let anyone know what they did and/or if it worked.  Apparently the hydroboost system has many symptoms and many possible fixes based on what the problem is.  For me, I cant seem to find anyone still available online who has the same exact pedal movement shutter.

[dripley]

I understand and have probably been guilty of that. My only symptom was groaning while turning. That is when I noticed it was PS fluid I was losing. I have a couple of oil leaks but this was adding to it. Noticed oil spots on the drivers side I had not seen before also, but  the brakes were functioning as they should. So our issues are not the same. Maybe the PS pump, dont know. Wish I could help more.

[Haggar]

Katoom,

 

Here is the cross section. 

 

The first movement is the brake pedal on the rod and taking up slack in the input rod.  You then start pushing the power piston (and output rod of the hydro) as the input rod/power piston is moving, the linkage to the primary valve is moving to apply pressure. 

 

So there is a lot going on in that first little bit of movement. Take things apart slowly and keep checking where your stickyness is.  You may be able to follow it to the exact piece that is hanging a bit.  Move master cylinder away first and check.  Disconnect input rod and check your pedal movement etc.

 

GL HTH 

 

Hag

 

[KATOOM]

Great idea.....  I'll pull off the master and see if the action is the same.  Good call Haggar.

[KATOOM]

Sooooo.....here's an update.  Disclaimer: I dont need to drive the truck (its become a garage queen in its old age) so that leaves my the opportunity to research research research before spending money on things that arent broken.  I know there are other people who use their truck for everyday use and I respect your needing to get things done much faster than how I handle things.

 

Nonetheless, what I came up with was all the tests indicated that there must be low fluid or air in the system.  Why and how I'm not completely sure but this is my "theoretical" opinion...

 

I think the screen and pressure valve on the pump was getting clogged up with sludge over years of use.  Even though I replaced most of the fluid about 30k miles ago, the hydroboost system runs HOT and takes its toll on the low volume of fluid.

 

In pointing that out, when I was towing the trailer up that long grade in the summer heat and the engine getting warmer than I've ever let it, I'm guessing that the fluid in the PS reservoir was too high (my fault) and spilled over.  Thats where the smell came from.  Then for whatever reason the system must have ingested a little air or created an air pocket either do to the fluid overflowing or because the valve screen was gummy which was causing more heat buildup and potentially a cavitating pump.  Lots of "theorizing" going on here...  Then after parking the truck that night the air burped and puked out more fluid and the pedal feedback was what I was getting after starting the engine.

 

So to test my theory I pulled the pressure line off the pump and pulled out the pressure valve.  I included pictures to show what I was working with...

You can see the screen which I cleaned after pulling everything apart, and you can see the small orifice and check ball behind it too.  Obviously not a lot of volume moves through the pump and I could easily see how any restriction of flow would cause problems for sure.  Also I dont know if that check ball is for one way flow but I could see how that could be affected as well if dirty.

 

Well I cleaned everything up and refilled the system.  Jacked the front axle on stands and started the engine.  Turned the wheel full clock a bunch of times and pumped the brakes, then shut the engine off and let it sit for a few hours as the fluid was now aerated, and thats what the directions say will happen too.

 

The next day I took it around the block and everything felt normal.  Brakes are powerful and steering is finger smooth.  BUT...when I came back from my short drive the hydroboost lines were already around 110* and it was only about 85* outside.

 

I know this topic has been hashed out before but I believe the hydroboost system on these trucks run way too hot and Dodge cut some corners by not installing a PS cooler.....which is something found on gasoline models and newer gen Cummins trucks.  So clearly a PS cooler is needed.  I've even checked my hydroboost lines over the years and seen temperatures on the lines in excess of 150*, so I can only imagine how hot it gets when I'm pulling a long grade in the summer.

 

So that said, I found a small PS cooler at NAPA and I think I'm going to install it to see if I can help the hydroboost system run a little cooler.  Thats about as far as I've gotten and sorry for the long posts...

[IBMobile]

Those power steering line get really hot to the point of giving me a 2ed degree burn and the car hadn't even been driven just idling for 20-25 minutes.   I see a lot of different cars and trucks with power steering heat exchangers. That's a good idea to put a small cooler in the system.  An inline transmission filter in the power steering return line would help catch that sludge and fine particles.    

[Haggar]

Yes our PS  systems get hot fast.  The reason is, it is always making pressure.  It is not demand sensitive.  So the pump is always fully loaded.  When there is no mechanical work to be done, it is all that horsepower going into heat.  (the pumped fluid has to go through the small orifice in the pressure relief constantly.)

 

I am going to add a PS cooler soon.  I have a manual transmission, so the area Not occupied by a transmission cooler is the perfect spot for me.  I am going to use the oil cooler from a Ford truck.  It is not perfect.  As I am going to add it to the return side of the power steering.  So my cooling will only be when the truck is being steered.  long idles, it won't cool.  (most of the factory systems worked this way, on the return line.  It is the simplest place, as the pressures are very low.)

 

We could add one to the pressure side and catch it in the loop for cooling all the time, but the heat exchanger will need to be rated for more than 1500 psi. (1550psi is our max operating pressure rating)

 

Many of the larger GM vehicles (Cadillac, Oldsmobile, Buick) had coolers in the PS system.  The were just small 2 pass units, but they were on the front engine bracketry, and caught the flow of the radiator cooling fan. (they too were on the return side)

 

Hag   

[Mopar1973Man]

Funny... From 2003 on up with the Ford steering boxes and ATF system required a cooler. But now 1989 to 2002 was a power steering fluid and didn't come with a cooler. Make you think a second. I'm at 354k miles still no issue with heat even driving 3 hours every other day. Just change fluid twice a year. Once in the spring and once in the fall.

[KATOOM]

I happen to be installing a small PS cooler on the steering box return line and mounting it in the area where the intercooler has a lot of open real estate.  I'll post pictures and results as soon as I'm done.

[NIsaacs]

On ‎8‎/‎27‎/‎2018 at 7:05 AM, KATOOM said:

I happen to be installing a small PS cooler on the steering box return line and mounting it in the area where the intercooler has a lot of open real estate.  I'll post pictures and results as soon as I'm done.

 

I think that is a good plan, I will be watching for the pictures. Here are a few pictures of my Hydro-Boost repair and a small writeup. It was just a small leak, not like your issue.  https://www.turbodieselregister.com/threads/weekend-maintenance-on-the-01.259915/#post-2558205

[KATOOM]

Thank you for that writeup link...  Looks helpful if I ever get to that point.

 

I did just finish installing a small PS cooler last night.  So obviously my data is limited.  As you can see it is little but I wasnt after much and I didnt want to impede too much of the intercooler.  I thought about mounting it somewhere underneath but was more interested in constant flow from the radiator fan.  I wish it wasnt so shiny silver but maybe some black spray paint will solve that problem.

 

That said, I did a quick check and I think its already lowering about 10* from what it was based on the drive distance and ambient temperature.  Not completely sure though and will be doing more checking in the hotter weather, which means I might not know until next summer.

 

[NIsaacs]

On ‎8‎/‎27‎/‎2018 at 5:10 AM, Haggar said:

Yes our PS  systems get hot fast.  The reason is, it is always making pressure.  It is not demand sensitive.  So the pump is always fully loaded.  When there is no mechanical work to be done, it is all that horsepower going into heat.  (the pumped fluid has to go through the small orifice in the pressure relief constantly.)

 

I am going to add a PS cooler soon.  I have a manual transmission, so the area Not occupied by a transmission cooler is the perfect spot for me.  I am going to use the oil cooler from a Ford truck.  It is not perfect.  As I am going to add it to the return side of the power steering.  So my cooling will only be when the truck is being steered.  long idles, it won't cool.  (most of the factory systems worked this way, on the return line.  It is the simplest place, as the pressures are very low.)

 

Hag   

 

Hag, I think the fluid is always flowing threw the return any time the engine is running. I think it is demand sensitive, it has to be. As soon as you step on the brake or turn the wheel, the return flow is diverted to assist the brakes or steering. What am I missing here?

KATOOM, that looks good, simple but effective. I have never checked my system for heat, I need to do that. I had an old '79 Ford F-250 with a cooler smaller than that. When I parked it after a few years in the log woods, I took it off and installed it on another Ford in the gas line to help with vapor lock.

[Haggar]

Nissacs,

You are correct (and what I was trying to explain)  The pump, when no flow is being used (by the brakes or steering) is trying to flow it's entire work THROUGH the relief.  So it results in a constant 1500psi available on the system.  (but all of this work is returning right to the pump to be heated up some more, and some more and more) 

 

Demand sensitive means if there is no flow (no need) (the steering is not being used, or your at higher speeds), there is no pressure (or as GM did, low pressure) when the computer calculates that you need more pressure it closes one relief valve and opens another giving a higher pressure only when needed.  (I have not seen that they used this with hydroboost, but due to the accumulator they may have been able to.)   I really liked this system (when it works) you could easily turn the steering at low speeds (backing a trailer, parallel parking) but at highway speeds, the steering was not overboosted.  The suburbasaurus never handles like a sports car, but the steering felt acceptable at higher speeds. 

 

The perfect place to put our coolers would be on the relief valve.  (this is where there is the most constant flow) (in real hydraulics we put coolers on the reliefs when they are a large portion of the total flow over time.)  But there is no easy way to do this with how they designed it.  It all happens in the reservoir of the pump..... 

 

HTH

 

Hag

[NIsaacs]

29 minutes ago, Haggar said:

Nissacs,

You are correct (and what I was trying to explain)  The pump, when no flow is being used (by the brakes or steering) is trying to flow it's entire work THROUGH the relief.  So it results in a constant 1500psi available on the system.  (but all of this work is returning right to the pump to be heated up some more, and some more and more) 

 

Hag

 

Thank you for your response, I understand most of what you are saying now, however, I am still resisting the above quote. The way I understand a relief, it is just that, a relief, and is only in use when the system is against dead pressure, brakes maxed out or steering at lock. That the pump flow is unrestricted via the return line. If the pump was up against 1500lbs pressure at all times it would cook in minutes. I do understand the 1500 lbs is available at all times, just not in use until assist is called for. Am I still missing something, lol