Foamy thing over the PAS hose

Peterv

Active Member
Hi All
Could someone or more shed some light on the significance of said foam around the PAS high pressure hose.
I'm sure I'd be correct in assuming it's for heat protection from the exhaust manifold But is it necessary?
I'm replacing the hoses soon so should I look into an alternative heat shield or just go do something else with my time?

Cheers, Peter
20200828_190915.jpg
 
I'm not sure if it's to protect the power steering fluid from heat from the engine/mani

Protect fuel lines from heat of the power steering fluid

or keep the temperature of the power steering fluid from cooling too much

Whatever it's there for I would suspect it is required or Rover would not have put it there :hmm:
 
Quattro, I agree, it must have been necessary. I replaced all the hoses in my PAS when I put my Blue Meanie back together, and the company who made up the new ones couldn't source anything like that. I've done without for eight years, and haven't noticed any degradation in the steering fluid or any other problem I can trace back to not having that foam shield on that hose. My original looked worse than the pic above, but not as bad as the knobbly greenish one we saw on another post just recently. It wasn't up to being transferred over to my new hose.
 
I fitted a NOS high pressure power steering hose to my Rover a couple of years ago. The foam rubber piece does not encompass the entire length of the hose over which it sits, so that to me suggests that heat protection is not its primary function. I am inclined to think that it is there more for either dulling resonance or to minimse vibrating against nearby components, including the vertical plastic fuel line. The hose over which the rubber sits has an increased cross section when compared to the rest of the hose. So there is an engineered reason as to why the diameter in this section required an increase.

The fluid in that section will travel with a lower velocity than throughout the rest of the hose as governed by the physics of fluid flow and the continuity equation. The continuity equation describes the conservation of mass within a pipeline. The product of fluid density with cross sectional area and velocity for each section of hose (based on diameter) must be the same, therefore it follows that with an increase in cross sectional area, the velocity must be lower.

As the power steering fluid is both compressible and viscous, Bernoulli's equation for fluid flow does not apply, although the energy equation does.
If we assume for just a moment that the power steering fluid is incompressible and inviscid, then as the velocity of the fluid decreases, so the pressure within the hose increases. With an increase in pressure does that mean that unwanted harmonics will also need attenuating. If it does, then possibly the rubber insulation is there for that reason.

Ron.
 
Ron, you lost me on the third paragraph :hmm:. But I see what your saying. Why the pipe gets fatter and needs that rubbery foam may probably only be answered by the engineers from the 60's or a hydraulic specialist.(sounds like that could be you:thumb:). When my new hose turns up from Wadham's I'll see if I can reproduce the foam for authenticity sake but will probably be black. The wide section of pipe is very close to the pump so pulse elimination is very possibly the reason. MrT maybe you could go have a feel for pulsing on that part of the hose next time your out and about with a helper to turn the steering wheel. Always like a mystery....
 
There is a hose cover called Firesleeve that is a heat resistant fibreglass/silicon tube that could be used here and look better.
Fire Sleeve Archives - RYCO Hydraulics
there will be equivalents from other makers - I know this one as I used to work there - NOT the same people as the filters, but related. You would need to have one end of the hose free to fit it. I have used this on fuel and power steering hoses in the engine bay of the 928. A pinhole in a pressure hose near the exhaust can ruin your whole day.
 
JP, found this place in NZ that has all sorts of cool things along those lines.
HeatSheild Products | NZ
If I can get the old foam off in one piece, I'll cover it with something pretty. That way it'll be the correct density for its original purpose. The old foams a little frayed around the edges but otherwise still flexible. :thumb:
 
Ron, you lost me on the third paragraph :hmm:. But I see what your saying. Why the pipe gets fatter and needs that rubbery foam may probably only be answered by the engineers from the 60's or a hydraulic specialist.(sounds like that could be you:thumb:). When my new hose turns up from Wadham's I'll see if I can reproduce the foam for authenticity sake but will probably be black. The wide section of pipe is very close to the pump so pulse elimination is very possibly the reason. MrT maybe you could go have a feel for pulsing on that part of the hose next time your out and about with a helper to turn the steering wheel. Always like a mystery....

Hi Peter,
I am actually a civil engineer, my master's thesis by research involves hydraulics ;).

You may well find that when your new hose arrives, it already has the foam sleeve fitted. It is also actually black when new, certainly my NOS hose has a black sleeve. There is no connection between the sleeve and the hose, it is free to slide, so your old sleeve could be removed, although it has likely glued itself on, my old one certainly did. I should be able to give you the dimensions of the NOS sleeve if you so wish?

Ron.
 
Hi Ron..Thought as much:thumb:
The photo's of the hose I've ordered don't show any fat part so i'm assuming no foam. I haven't tried too had as yet to move the foam but the top couple of inches does move so touch wood... I'll wait till I have everything in my hot large hands before going further with this. Nothing more annoying having a car in bits waiting for parts to turn up:mad:
 
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