Power steering mystery (1 Viewer)

[badmuthatrucka]

Okay, so this has me stumped. I bought my '93 FZJ80 back in '06. In the summer of '07 I went on a wheeling trip around Colorado. When we ran Chinaman Gulch, I hit an obstacle a little too hard on the passenger-side front and the low-pressure return line on the PS Gearbox blew and I lost all of the fluid. I limped the cruiser over to Buena Vista, with a lot of whining from the PS system, and got some more hose and fluid from NAPA, and everything seemed to be fine for a long time.

Summary: The hose burst but there was a reason.
Weather/Fluid levels: Warm weather (70-85 F), and started with plenty of fluid.

Fast forward to last October ('12), when the same hose blew again while driving on a paved road under normal operating conditions. No sudden and sharp changes in direction forced by unseen obstacles. I limped it back home, with a lot of whining from the PS system, and replaced the hose without giving it a second thought.

Summary: The hose burst without an obvious reason.
Weather/Fluid levels: Cold weather (25-40 F), and started with plenty of fluid.

This past summer (August '13), I ran the Middle St. Vrain and Coney Flats trails, and another unseen rock forced a full turn of the steering wheel, and the same hose burst again. I limped it back home to Longmont, with minimal whining from the PS system, and replaced the hose and fluid. In order to ensure that the hose wasn't getting rubbed or cut by anything in the engine compartment I wrapped it in some hard-plastic wire loom in the area that the hose had burst.

Summary: The hose burst but there was a reason.
Weather/Fluid levels: Warm weather (75-80 F), and started with plenty of fluid.

This past Thursday (November '13), my wife was running errands around town with the kids, and everything was fine for at least 30 minutes of driving. She had to pick some things up at Mal-Wart and once she came back out, the steering was suddenly extremely hard, and she had to perform a 6-point turn to get out of the parking space. She limped it back home, with almost no whining from the PS system at all. I checked it yesterday (Friday) and found that the same hose had burst. There was no damage to the wire loom, and the hose had burst in roughly the same spot, directly underneath the wire loom. I replaced the hose, this time with a longer section and formed a loop just so it might be easier to see the hose when and where it bursts again. I have driven the cruiser around today, with the steering remaining stiff after 30-45 minutes of driving.

Summary: The hose burst without an obvious reason.
Weather/Fluid levels: Cold weather (0-15 F), and started with plenty of fluid.

I cannot accurately recall the location of the rupture for the first two instances, but the last two have been close enough together that I can say with certainty that the location has been in roughly the same spot both times. The location has been about 2-3" from the end of the Return Pipe on the gearbox, this is the near-horizontal pipe below the PS reservoir.



It is low-pressure and should not have to be steel-reinforced as far as I can tell. I have replaced the hose each time with 3/8" PS hose from NAPA or Advance Autoparts. I am concerned that the system is no longer making noise when there is no fluid.

So here are my questions:
What could the problem be that would cause the hose to burst so often and in the same place?
Should I try replacing the hose with an OEM hose from Mr. T?
Do I need to rebuild/replace the PS gearbox?
Has anyone experienced something similar?

 

[badmuthatrucka]

Anyone? Anyone? Bueller?

 

[jonheld]

In every case you have documented there is absolutely no reason for a hose to burst.
It sure sounds to me like you're using the wrong type of replacement hose.

 

[Elbert]

are you using the same vendor for the hose you have noted failing multiple times? What's the common factor in the story....the same hose? On the surface I don't understand why the low pressure hose would "fail" due to pressure....that in itself does not make sense.

 

[inkpot]

Did the hose "burst" or just crack? Big difference. I have replaced about a dozen sets of low pressure hoses on 80s in the last year and a half. One due to it had failed/cracked. The others because they were hard as a rock and doomed to crack if they were not replaced soon. Most of these were OEM hose that were probably original. Make sure that you are getting TOC/ Transmission Oil Cooling hose. It should be marked on the hose. John

 

[86tuning]

Or perhaps try the blue racecar stuff that's got a working pressure of 250psi when used with the proper fittings. 3/8" is same as -6AN (called dash-six push-on hose) and should work, but will be a fight fit.

I'd avoid the braided stainless stuff, the blue push-on will be much easier to install.

 

[cruiserbrett]

This is likely not an issue of pressure rating on the return side of the hose. Unless there is a restriction somewhere in the system, its not really a pressurized system on the return.


I am having a tough time recalling the exact routing, but I think its PS gearbox-hose-"paperclip cooler"-hose-reservoir.

Which hose blew? Assuming you meant literally the hose from the gearbox to the cooler, I would imagine there is a restriction upstream. As in a dented paper clip cooler, or a severe kink in the cooler to reservoir hose? or even a defect in the nipple to reservoir? could be a chunk of hose jamming up the flow somewhere in the system. a check with some air flow(slowly blow PS fluid out before running air through at full pressure) should give you an idea.

On another note, I have replaced my return hoses because of serious external oil contamination from an oil pump cover leak that really softened up the external wall of the hose. It was nearly malleable after years of being soaked in engine oil on the outside.

 

[kerrye]

I've gone thru 3 high pressure lines in less than 20k miles. No accounting for that either.

 

[inkpot]

I've gone thru 3 high pressure lines in less than 20k miles. No accounting for that either.

Are they OEM?

 

[kerrye]

Are they OEM?

No. Couldn't justify that $300+ for the Toyota part. Can anyone give the details of the differences between the Toyota hose and the aftermarket hoses. The original Toyota hose failed.

 

[86tuning]

No. Couldn't justify that $300+ for the Toyota part. Can anyone give the details of the differences between the Toyota hose and the aftermarket hoses. The original Toyota hose failed.

There's another thread about the return hose from the cooler. Cdan mentions that there is a replacement hose for that application for $26. I wonder if he knows what may fit in the spot you describe.

 

[badmuthatrucka]

Did the hose "burst" or just crack? Big difference. I have replaced about a dozen sets of low pressure hoses on 80s in the last year and a half. One due to it had failed/cracked. The others because they were hard as a rock and doomed to crack if they were not replaced soon. Most of these were OEM hose that were probably original. Make sure that you are getting TOC/ Transmission Oil Cooling hose. It should be marked on the hose. John

The hose burst. It was far too new to have cracked. What concerns me now is that the PS system is full of fluid, but the steering is still as hard as when there is no fluid at all. Is it time to find a replacement gearbox and rebuild this one?

 

[badmuthatrucka]

In every case you have documented there is absolutely no reason for a hose to burst.
It sure sounds to me like you're using the wrong type of replacement hose.

Actually, in two of the four cases, hitting an obstacle which forced a hard and sudden change in direction is the likely culprit for the burst hose. The other two times I have not been able to divine a reason for the hose bursting. I have made sure to get power steering hose each time.

 

[badmuthatrucka]

are you using the same vendor for the hose you have noted failing multiple times? What's the common factor in the story....the same hose? On the surface I don't understand why the low pressure hose would "fail" due to pressure....that in itself does not make sense.

The first hose was 'yota original. The setting hose was from NAPA, and the third and fourth were from Advance autoparts. So three different vendors. However the worst result (most frequent failures) is from the Advance hose, roughly 3 months between replacements.

 

[badmuthatrucka]

...
I am having a tough time recalling the exact routing, but I think its PS gearbox-hose-"paperclip cooler"-hose-reservoir.

Which hose blew? Assuming you meant literally the hose from the gearbox to the cooler, I would imagine there is a restriction upstream. As in a dented paper clip cooler, or a severe kink in the cooler to reservoir hose? or even a defect in the nipple to reservoir? could be a chunk of hose jamming up the flow somewhere in the system. a check with some air flow(slowly blow PS fluid out before running air through at full pressure) should give you an idea.

The hose that burst, as illustrated in the picture in the original post, is the one that goes from the gearbox to the cooler. If I understand correctly, that would mean that the direction of flow in this hose is from gearbox/firewall to cooler/radiator. From past experience, it usually seems that if there is a blockage in a hydraulic system, the failure due to back-pressure would be closer to the blockage, or just up-stream, barring a defect in the hose. The rupture seems to be consistently just down-stream from the tube that comes out of the gearbox. I will have to take a look at the tubes going into and out of the cooler this week.

Thanks for the idea!

 

[badmuthatrucka]

Any idea as to why the system would be so stiff still? Could that be caused by a blockage up-stream from the gearbox, but down-stream from the pump? Should I check for a blockage between the gearbox and the down-stream side of the cooler first, or start looking for a replacement gearbox first?

 

[86tuning]

stiff steering could be lack of fluid, or possibly failed pump. More likely lack of fluid flow.

 

[inkpot]

High pressure goes from pump to box. Then fluid goes thru paperclip cooler and then back to resreviour. It would take a lot of back pressure to blow a high pressure line. You definitely have some blockage at the box or in the cooler if your blowing the low pressure line between the box and the cooler.

 

[jonheld]

Actually, in two of the four cases, hitting an obstacle which forced a hard and sudden change in direction is the likely culprit for the burst hose.

I'm calling bull**** on that statement. I've been wheeling for 20 years and have never heard of that happening. I've also been known to hit a rock occasionally. My original OEM lines were replaced when I replaced the radiator, as the high pressure line had been weeping for quite some time and the low pressure line was cut by the alternator fan about 8 or 9 years prior. It was replaced with fuel line.

 

[Mixelplix]

The hose burst. It was far too new to have cracked. What concerns me now is that the PS system is full of fluid, but the steering is still as hard as when there is no fluid at all. Is it time to find a replacement gearbox and rebuild this one?

I would take a guess that running the pump without fluid caused it to wear. Now it's not generating pressure which is why you have stuff steering even though it's filled.

Pump rebuild is my guess on this subject.