Power brakes and steering probs!

[Subzilla]

FINALLY finished the 6.2 install back into the 83 Sub. Engine runs great although a little bit too much clatter and black smoke for my liking. Need to make some adjustments.

In the process, I replaced the PS pump because the old one was leaking and the steering will get quite stiff with multiple movements as if the power assist is leaving.

This morning, the brakes went partially to the floor with a hard braking episode. And the steering seems to be getting stiffer. Could this be a defective PS pump or would the brake booster be going out? How would one diagnose the cause?

Could it be as simple as still having some trapped air in the system? Again, the steering was acting up prior to the PS pump replacement.

[Subzilla]

UPDATE: Still trying to diagnose the steering problem. Works great for the first 30 minutes of driving, then when the steering wheel is turned more than a complete revolution, it really stiffens up and almost pulses. Does fine with short steering movements.

Steering pump was replaced a month ago with a reman unit.
Just replaced 30 year old pressure hoses last night thinking these might be deterioriated and possibly causing a blockage.

Steering gear box?
Hydroboost?
Bad remanufactured pump?

What's left?

[convert2diesel]

Sometimes takes a while to fully bleed the PS system, especially with the hydroboost. Reservoir is below the high point in the system (hydroboost) so air can get trapped up there.

With engine running, cycle the steering lock to lock while pumping the brakes. Repeat as required. Keep a good eye on the reservoir level. and never let it drain below the return line or you will be repeating the process. Ask me how I know.

Bill

[joeq]

So I guess you learned the hard way, aye Bill? :)

[Subzilla]

This hard steering was starting to occur prior to the pump replacement. The truck sat for 9 months while I replaced the engine (these things take time!). I replaced the pump with the engine. Now the condition is worse.

And why would it only act up after it seems to be warmed up?

I will try to keep bleeding the air to see what happens.

[sctrailrider]

Have you flushed the system and put new fluid in it.

[convert2diesel]

This hard steering was starting to occur prior to the pump replacement. The truck sat for 9 months while I replaced the engine (these things take time!). I replaced the pump with the engine. Now the condition is worse.

And why would it only act up after it seems to be warmed up?

I will try to keep bleeding the air to see what happens.

When I did the Buick, it would wait till I drove 20 miles into town and in traffic before the brakes and the steering gave up the ghost. Good for an adrenalin rush but did cause some interesting situations for a few days :eek:.

The spool valve in the hydroboost unit may be sticking. The Steering box gets pressurized oil from the hydroboost (pump to hydroboost to steering box) through the spool valve. If that is sticking, than little or no pressure to the steering box. Have seen a Hummer where if you took the steering to lock, the brakes would come on. Reverse of your issue but again a spool valve issue.

Your problem was more than likely the hydroboost spool valve from the beginning, by your description, probably caused by the unit sitting for so long. Really flush it out with new PS Fluid. Pretty close tolerances in there and combined with air still in the system it is probably hanging up after the fluid heats up.

Have rebuilt a couple of these units over the years but don't know if GM still stocks the kits. Expensive for exchange units but, for what it's worth, I have never not been able to free up the spool valve. Usually a very dependable unit. I only rebuilt them to be sure.

Bill

[Subzilla]

I put new fluid but did not flush the entire system. Only replaced fluid that drained out from the pump, reservoir and lines which seemed like a lot. I expect the only old fluid left was in the hydroboost.

Never flushed a PS system. What is the procedure? Sorry for asking...

[DmaxMaverick]

A PS system flush is simple, and recommended a LOT more often than anyone really does it.

From This Thread (http://www.thedieselpageforums.com/tdpforum/showthread.php?t=41239) (another issue, but the procedure is the same):


To trade out the fluid, disconnect the return line from the hydroboost (spring clamp line at the top, not the nut fittings), and install a length of hose that can be routed away and into a container (secure the hose ends!). If you are doing it solo, place it so you can see it from the driver seat. Idle engine until the pump makes a little noise (picks up air), while slowly pumping the brakes and cycling the steering, lock to lock (it helps if the front wheels are off the ground). Stop engine, fill reservoir and repeat. Do this until the fluid coming out looks like the fluid going in. Add the ATF additive AFTER the last cycle, then top off with the ATF. Restore the return line. Idle the engine while cycling the steering and pumping the brakes, then top off as necessary. The air will find its way out.That was for a late model truck, but the procedure is the same for all Hydroboost equipped trucks. Also, I recommend using synthetic ATF, rather than PS fluid. It's less expensive, and I've had much better service over the years using it. Fewer leaks and longer service of all the parts. I also recommended the use of a transmission fluid conditioner to address a minor leak. You can omit this if the system is relatively new, or use 2-3 ounces of "Trans-Medic" additive if it's more than a couple years old. Doesn't hurt, if you do, and often helps free up internal valves and seal external leaks. I've never had a need for additive when a new system is started with synthetic ATF.

[Subzilla]

Oh heck! That's all there is to it? Will definitely try it and let you guys know how it works out but it will be at least a week from now after a much needed vacation at NC's Outer Banks.

Thanks for the thread link and explanation.

[sctrailrider]

The Outer Banks... nice, I see there is a little storm building out in the big water now and will be coming our way next week.. Good luck and stay safe..

[Subzilla]

Great family vacation at the Outer Banks. Now it's back to reality!

SO, I flushed out the PS system with 3 cycles of PS fluid per the instructions above. Then put synthetic ATF and flushed out another cycle all the while pumping the brakes and cycling the steering. Then topped it off with ATF and repeated the air bleeding until the fluid level stabilized. Test drove it and I still have the exact same problem - turn the steering wheel a little more than 3/4 turn and it looses power. I noticed tonight that it will do this when turning the wheels into the turn but doesn't seem to do the same when it goes back to center. It seems to be starting this condition quicker the more I drive it, like it's getting worse. Initially, it would take 30 minutes of driving and now it's about 5 - 10 minutes.

To recap, the PS pump was replaced with a reman unit but I had the beginnings of this condition prior to pump replacement.
The pressure hoses were replaced.

Steering gear box?
Hydroboost unit?
Any other way to free the sticky spool valve, Bill? If that's the problem?
Any other suggestions?

The hydroboost unit was probably factory installed in 83. 340k miles.

[DmaxMaverick]

The HB unit is probably due for replacement, according to the mileage. However, your issue is dependent on steering wheel revolutions, which indicates the steering box. Or both. If it were the pump, it wouldn't matter much how you turn the wheel, and the brake assist wouldn't work. If the brake assist works all the time, especially when the steering is acting up, it's the steering box.

[Subzilla]

That explanation makes some sense to me. I think I would rather replace the steering box rather than the HB unit based on what I've read about reaching the top 2 nuts under the dash. The steering gear box is a reman unit with a lifetime warranty so no costs invovled and no big deal to spend an hour replacing that. Done it before.

Will put that on my weekend chore list and let you guys know. Thanks!

[More Power]

Replacing the steering box will likely make an improvement in steering due to wear of the original one. Let us know how it goes.

Jim

[Subzilla]

No real update yet on the steering other than it is still the same. Was planning to replace the steering gear box. Been busy diagnosing my brake issue which I can't help to think might lead to the hydroboost. Wanted some opinions.

The Sub sat for 9 months while I replaced the engine. The stiff steering was slightly there prior to the engine replacement but got worse after sitting. My brakes started acting up after the 9 month sitting. With hard braking, the pedal will almost touch the floor and still without full braking power. Seems to feel fine under normal braking. The pedal has a mushy travel section after the normal braking point, then it firms up but only when it's at the floor.

Things done/replaced:
Replaced master cylinder with rebuilt unit from Advance Auto.
Rebuilt MC leaked from the rear so after a month, replaced with another AA rebuilt unit. Completely bled the brakes after each MC replacement including bench bleeding.
Flushed hydroboost 3 times and filled with synthetic ATF.
Replace rear, center rubber brake line.
Tonight, pulled drums and adjusted brakes out. They were quite out of adjustment. Wheel cylinders appeared nice and dry.

Drove to a dirt road (those are getting harder to find here in Concord, NC), slammed the brakes on and just barely got skidmarks only after the pedal goes through the mushy region. Not good for a panic stop. I know it wouldn't lock up on dry pavement.

I'm at a lost (and very frustrated) as to what to check next. Could I have 3 bad master cylinders? To check the Hydroboost, I pumped the brake to get rid of the pressure with the engine off. Depressed the pedal, started the engine. The pedal goes down but seems to hit the mushy region and won't pump back up like it's suppose to. Could this and the sporadically stiff steering signify a malfunctioning HB?

[DmaxMaverick]

It sounds like you have multiple simultaneous issues. Maybe not.

3 bad MC's? Unlikely, but stranger things have happened.

Air in the brake lines/caliper(s). Sounds like, despite your efforts and everything else.

Also consider whatever the problem is with the brakes and steering, one will almost always affect the other, in some way.

The brake pedal should not go to the floor w/o sufficient pump pressure, and good HB operation. When it does, you should feel significant pedal vibration, hear a little HB squeal/hiss, and hear the PS pump struggle/growl a little. Make SURE the belt isn't slipping, or it will "limit" the available pressure and fluid volume (causing poor braking and hard steering). A much less common possibility may be a PS pump pulley slipping on the shaft (it won't do this long before it becomes REAL obvious).

We're still here with you. Keep at it!

Also, I have a NIB pump, if you need a good one for testing. It's old stock (1990-ish), OEM, never installed, properly stored. If the 83 and 85 are compatible (I think they are, but haven't confirmed), you're welcome to try it for the cost of shipping. If it helps, we can work out details later. I bought the pump back then, incidentally, working on a problem similar to yours. I had 3 or 4 bad (aftermarket) MC's, before replacing with OEM and finding success.

[Subzilla]

Hey thanks for the PS pump offer. I have a NAPA lifetime warranty on the one I just installed so I can always take it back.

Driving the thing this morning, the brake pedal has a very consistent pattern: normal braking, then a little more foot pressure yields a mushy range, then it firms up or maybe even stops at the MC maximum limit?? I agree with you, it sure feels like air in the line. This condition has stayed the same through the MC changes. No worse, no better. You think I should replace the MC again? I'm through with the rebuilt crap and will go with new this time.

Other times when I had air in the lines, IIRC, the pedal had a more consistent sponginess and it didn't flucuate like mine does.

And would you replace the PS pump? My last plan of action with the steering issue was to replace the gear box.

I will check for a loose PS belt but I have not heard any belt squeal. Come to think of it, I haven't touched that since the engine went in. I know belts stretch. Will also inspect the pulley.

If the Hydroboost is malfunctioning, wouldn't the brakes loose power and therefore become stiff? As if the engine were turned off? Sort of like what is going on with my steering.

Thanks for your responses.

[convert2diesel]

Grasping at straws here but have you checked the front (I assume) calipers? Sitting that long, your calipers may have seized causing your mushy feel as the pistons try hard to bend your rotors. Proportioning valve is biased to the front so most of the umph goes forward.

Just a thought.

Bill

[DmaxMaverick]

It's difficult to say without getting hands on. I'd just take each symptom one at a time, starting with the most profound, and eliminate the possible causes. Eventually, you'll have a list of causes, or they will tie back to a common cause.

Something I didn't mention earlier is the possibility of a broken caliper. It doesn't happen often (almost never), but when it does, it can seem like air in the lines, more similar to a near rupture of a hose. You'll have to watch the calipers while someone stands on the brake pedal. Any break/crack should be obvious. The caliper shouldn't move once slight pressure is applied and engages the rotor. A seized caliper adjuster can also cause this, and can lead to a broken caliper or bracket.

[john8662]

I hope you figure it out cause I got one doing the same thing...

Just got my 1989 V2500 4x4 Suburban running because it had no engine for a long time. I just put a good used 6.2 in the Suburban and noticed a few things.

The power steering is stiff like yours.

I know that there is a brake leak because I had to add fluid to the rear brakes. I'm going to replace the rear wheel cylinders and bleed the system and see if this fixes the problem. I know the brakes need fixing anyways. I'm not driving this one, so it's a deal when I get around to it thing...

How are you bleeding your brakes?

I used to think you could get it done with one of those Mighty Vac vacuum hand pumps, but found it doesn't actually get all the air out. I just do the whole get a helper to pump the brakes and bleed manually there until the fluid is clean and completely air free on all 4 corners. Best brake feel after that.

J

[Subzilla]

I had intended to check the front brakes last night but ran out of time. Couldn't do it tonight, maybe tomorrow night. What you guys say makes sense. I really hope I find something causing the problem there in the front.

Yup John, bleed them the old fashioned way. I have the wife trained to pump the pedal 3 times and hold. I also tried the Mighty Vac pump and wasn't happy with the results. Wore my hand out squeezing the handle. Seemed to take longer, too.

Believe me, when I figure all of this out, I'll let everyone know.

And forgive me if I sound a little frustrated or eager in previous posts. It seems all of my old stuff is breaking. Wife says I have too many vehicles - maybe she is right. Right after getting the Sub engine started, my son's 2001 S10 Blazer diff imploded. Had a shop fix that. The same vehicle is having long crank times on cold starts. Same symptom my 93 Jimmy had when the fuel pump was failing 2 different times. Haven't fixed the Blazer yet. And just 2 weeks ago, the 94 K1500 won't move up the driveway in drive. Reverse seems to work fine, just major slippage in forward. Parked it and haven't messed with it yet. Plan to pull the pan. All of this while messing with the Sub brakes and steering. Started looking at used 2012 and 2013 Silverados on the web.........

[convert2diesel]

I have found over the years that gravity and time is your friend when bleeding brakes. Open the bleeder and let the fluid fall out on its own. Takes time, and you have to keep your eye on the reservoir, but the results have always been better than any other system.

Used to pressure bleed brakes backwards from the wheel back into the reservoir but with the new ABS systems I'm always afraid of trapping air in the pump body so back to gravity. Wish I drank beer. Would give me something to do while I watched brake fluid fall out of my vehicle.

Bill

[Subzilla]

Got the issue fixed. Sorry for the late response!

The stiff steering issue turned out to be a bad steering pump. With the engine replacement, I put on a rebuilt PS pump from NAPA which kept me thinking this couldn't possibly be the problem. Finally decided to replace it (lifetime warranty) and lo and behold, the problem totally went away.

I think the fading brake pedal also seems to be better. Still experimenting with that. So I guess the PS pump just wasn't supplying enough stuff to the hydroboost unit.

The thing is much easier to drive now! Thanks for the help!