Hydro-boost or power steering pump problem or worse...?

[vilago]

so i just bought a 92 6.2L and the PO was explaining to me that the hydro-boost (as i've now known it to be called) is leaking badly, and it is pretty obvious by the fluid stains and drips. he then directs my attention over to the starboard side of the engine bay and shows that the power steering pump is kind of making this "knocking" noise (says he's pretty sure it isn't the engine, and I don't think it's the engine either because blow-by is PERFECT and i don't really have any smoke at all) sort of a loud repetitive clunk/tap noise. the noise only starts when the truck is warmed up. he says he thinks the hydroboost might be causing the power steering pump to make noise via indirectly leaking oil into it internally somehow. i don't notice any major issues with the steering or braking btw. well, anyway long story short i bought the truck for a decent price and drove it 80 highway miles to home. i still don't notice any problems other than what i've described ( a lot of black drips in the parking lot though). could both my hydroboost AND power steering pump need attention or do i have bigger problems? (owner thinks that replacing/repairing hydroboost may clear up the clunking noise).

[vilago]

i guess my main thing is that i've never heard of a power steering pump "knocking" before. i guess it is possible, but since it is the device pumping the fluid, i don't see how the hydroboost can make it fail. does anyone out there have any experience with the hydroboost and/or steering pump?

[rustyk]

I had Rusty's Excellent Hydroboost Adventure about 20 mos. ago (issue was neither the Hydroboost nor P/S pump, but leakage at the shafte brake actuator).

One symptom I had was aeration of the P/S fluid, and there was no knocking even with air entrainment.

I'd suspect the crankshaft damper, as I did have that symptom, and the knock was caused by the rubber so badly deteriorated the damper was hitting its metal stops.

[DmaxMaverick]

I had Rusty's Excellent Hydroboost Adventure about 20 mos. ago (issue was neither the Hydroboost nor P/S pump, but leakage at the shafte brake actuator).

One symptom I had was aeration of the P/S fluid, and there was no knocking even with air entrainment.

I'd suspect the crankshaft damper, as I did have that symptom, and the knock was caused by the rubber so badly deteriorated the damper was hitting its metal stops.

Close, I think, Rusty. The balancers die silently, or catastrophically. The pulley, on the other hand, sounds like a power steering pump thats bad, to someone who doesn't know what one sounds like.

Remove the belt and see just what moves around, that shouldn't. If the outer ring of the balancer moves, it's bad. If the pulley moves a couple degrees w/o the crank, it's bad (probably the problem).

Now, to lend credence to the PO, the hydroboost unit can cause the PS pump to fail. The HB unit manages the pressure and flow for the brake and steering assist. If it's leaking badly, it's bad, either way. An overworked PS pump will fail much sooner than it should, and a bad HB unit will overwork a pump.

[vilago]

Close, I think, Rusty. The balancers die silently, or catastrophically. The pulley, on the other hand, sounds like a power steering pump thats bad, to someone who doesn't know what one sounds like.

Remove the belt and see just what moves around, that shouldn't. If the outer ring of the balancer moves, it's bad. If the pulley moves a couple degrees w/o the crank, it's bad (probably the problem).

Now, to lend credence to the PO, the hydroboost unit can cause the PS pump to fail. The HB unit manages the pressure and flow for the brake and steering assist. If it's leaking badly, it's bad, either way. An overworked PS pump will fail much sooner than it should, and a bad HB unit will overwork a pump.

I know i have to replace the HB unit, that is a given. however when you refer to "balancer" i'm assuming that's another term for the crankshaft damper? and can you be more specific with the term "pulley"?

[vilago]

I know i have to replace the HB unit, that is a given. however when you refer to "balancer" i'm assuming that's another term for the crankshaft damper? and can you be more specific with the term "pulley"?

wait sorry i think i know what you are talking about. it seems i have to remove the crankshaft pulley to get to the damper (balancer) anyway so if i'm donning the rubber gloves and going in there i might as well replace both of them. any way i can know one way or the other what the problem is before jumping in head first?

[DmaxMaverick]

Yes. Balancer = Dampener. Also, harmonic balancer.

The pulley is like many motorcycle rear hubs. An inner hub, and an outer hub, with rubber insulators between them. When the rubber wears out, the outer is allowed to travel a bit around the inner, until the metal that previously supported the rubber makes contact. The violent combustion pulse of a Diesel engine really exaggerates this. When cold, the combustion is much less aggressive, and the timing is so as to minimize heavy knock, which is why they make less noise when cold (than they could). The crankshaft pulley has an inner hub bolted solid to the balancer inner hub, and has the actual pulley part of it attached to it with a bearing (bushing), which allows it to absorb the combustion pulse. Once the rubber is worn out, the outer pulley will not be "in time" with the inner, causing it to clash with each combustion event.

Remove the belt and grab the pulley. Rotate it back and forth, without rotating the crank. If it moves, it's bad. Often, it will actually wobble, which indicates it's really bad.

Late models (gas or Diesel engines, such as the Duramax) incorporate the pulley into the outer ring of the balancer. The results when one wears out can be the same, only with less parts.

[vilago]

Yes. Balancer = Dampener. Also, harmonic balancer.

The pulley is like many motorcycle rear hubs. An inner hub, and an outer hub, with rubber insulators between them. When the rubber wears out, the outer is allowed to travel a bit around the inner, until the metal that previously supported the rubber makes contact. The violent combustion pulse of a Diesel engine really exaggerates this. When cold, the combustion is much less aggressive, and the timing is so as to minimize heavy knock, which is why they make less noise when cold (than they could). The crankshaft pulley has an inner hub bolted solid to the balancer inner hub, and has the actual pulley part of it attached to it with a bearing (bushing), which allows it to absorb the combustion pulse. Once the rubber is worn out, the outer pulley will not be "in time" with the inner, causing it to clash with each combustion event.

Remove the belt and grab the pulley. Rotate it back and forth, without rotating the crank. If it moves, it's bad. Often, it will actually wobble, which indicates it's really bad.

Late models (gas or Diesel engines, such as the Duramax) incorporate the pulley into the outer ring of the balancer. The results when one wears out can be the same, only with less parts.

I understand. I had to see a picture of it to see how it was laid out, but i get it now. i'll check that in addition to the PS pump and hopefully i can sort this out and get at least 100K more miles out of this truck. thanks a lot! :)