Power Steering Fluid Temps

[BMWTurbo]

brakes sticking due to PS temp??

The brake booster is a hydraulic unit fed by the PS pump. My testing indicates that when the PS fluid reaches a certain temp under the bonnet is cases something in the hydraulic system to 'stick on' and not relieve.

I have tested the calipers under this condition and the pistons can be moved back into the caliper with some levering like normal. Obviously the bay etc can cools during this period so the drag on the front wheels is less pronounced then when hotter. but the calipers don't feel sticky at all.

I can't see how the ABS unit could create this effect and the brake fluid should be able to handle higher temps then the PS system.

[BMWTurbo]

The groan you are hearing, does it occur when you first input some lock? Ie, hold the wheel constant, then start winding on some lock, noise occurs?

If so, then it's a very common noise in production car systems, and has to do with the valve balance, ie the amount of holes that line up perfectly in the valve body when it's first cracked open. It's actually known as "grunt", and OEM's put a lot of effort is put into eliminating this noise, which is essentially a production tolerancing issue between two very precisely machined components. Very common on 90's power steering cars and earlier. Dont' hear it much on modern cars.

John :- it will do it when first moved as you outline above.

The Flow Control Valve didn't seem to have a mark of any description on it that I could see it was free to rotate inside the sleeve.

I'll look back over a procedure I have to see if it advises to align it specifically.

I know RZ had some issues bleeding his system, but most supra's/Aristo's don't seem to have this noise.

One thing I clearly ID's last night was that after the flexible section of the PS outlet hose I could CLEARLY feel the vane pump pulses in the distribution block and hard line. I will get the line replaced with non-hydraulic line and see if that cures it.

[John]

bmw, you cannot do anything to stop this noise, if it is what I said it was. It's a manufacturing/design "fault" if you like, nothing to do with the ease of the which the spool rotates in the sleeve. A lot of manufacturers had the problem, and it's taken years to solve basically. The valve is balanced on a special machine when it's assembled, and once the middle of the boost curve is found, the torsion bar is then pinned together with the spool. It was only with a lot of development on the shape of the feather edges on the valve slots was the noise eliminated so it wasn't so sensitive to getting the middle of the boost curve spot on. Most people don't notice it. I'm afraid you're stuck with it like that.

[BMWTurbo]

Thanks John.

I this I will get the flexible section of the hose changed anyways as my car is noisier then every other 2jz equiped vehicle I've heard.

[BMWTurbo]

No Joy... Fuckin thing still sticks the brakes after idling in traffic for a prolonged period.

Water temps didn't climb past normal, but the brakes started to stick again yesterday.

I know exactly when it's about to happen as the brake pedal goes hard as if it hasn't released and it turns to shit after this.

Engine temps do rise as I need 30% throttle to move the boat down the road against the sticky brakes.

I checked the temps when I got home :-

Master Cylinder - 67 deg C
ABS Unit - 67 deg C
PS Fluid temp - 70 deg C

I let the car idle with the bonnet up for a couple of mins and the brakes go back to normal. So it's heat related, but I can't put my finger on the actual component that's causing the problem.

Attached is a good diagram of the system.


http://bmwe32.masscom.net/maxf_website/booster.htm

Suggestions?

[Gammaboy]

I've had a similar issue in a remote booster equipped setup - in my case its the master's piston hanging up in its bore.

[BMWTurbo]

Was it temperature related Gamma?

I might have to bend over for a wrecker and get a spare hydraulic booster and master cylinder.

[rowdytoot]

I reckon based on that diagram, that your toyota P/S pump is getting the hydrualic fluid too hot, and it's expanding the fluid in the hydraulic brake booster and therefore pushing the master cyl piston and locking on the brakes.

maybe it needs a bigger cooler with a fan on it running constantly.

[BMWTurbo]

rowdy, do you think the PS fluid at 70 deg C will expand and create more pressure then the PS pump does against it?

From memory Trans fluid temps of 80 deg C are fairly normal?

[Gammaboy]

Was it temperature related Gamma?

I might have to bend over for a wrecker and get a spare hydraulic booster and master cylinder.

Nah, but you'd walk away from it for a while and come back and it would come good. But it could sometimes be forced into coming good by tapping the brakes.
not going to be a problem soon, going to piss off the remote boost and run manual brakes - who fuckign needs a booster on a 900kg car.

[rowdytoot]

rowdy, do you think the PS fluid at 70 deg C will expand and create more pressure then the PS pump does against it?

From memory Trans fluid temps of 80 deg C are fairly normal?

I dunno probably not really.- it's just a guess cos system has the PS and the booster linked. The change you've made over stock is to run the toyota PS pump. Are their instances of something similar happening with in a stock set up- may point to something to do with teh booster??

(I'm only thinking about the brake issue here)

[jzx83]

How difficult would it be to bolt the BMW PS pump onto the JZ?

Like making mounts difficult or 'that thing won't physically fit in there' difficult?

I seem to recall something about your conversion involving deletion or changed method of achieving speed sensitivity. So i suspect you may have had another good reason for going with the Toyota Pump, other than the ease of bolting it in.

Just wonder whether the extra heat in the PS is more due to the 'wrong' pump being used, or whether it is more to do with a hotter engine sitting in there.

Edit:
Oh, and as seems to have occurred to some others - is the brake system actually 100%?

John: Where in the system is this booster that you talk of having the 'grunt'. I'd have assumed that it was part of the steering box, could he use a later/reco'd/wrecker box and possibly eliminate this noise?

[BMWTurbo]

Cheers for the thoughts gents. Not dissmissing any suggestions just trying to get my head around how they might affect the system.

I've tried tapping the master cyl / booster but didn't notice it freeing up as such Gamma. I might keep a block of wood handy and see if I can 'free' it when it does it next as a check.

True Rowdy re change but I'm now running a 'larger' engine that fills the bay more and is using a thermo fan rather then a nice powerful engine fan, the front of the engine is very close to the fan also, which will be severly impeding the ability for hot air to exit the bay.

jzx83 :- I retained the Toyota PS because is was already attached to the engine and comes fitted with the factory idle up pressure valve.
The BMW pump sits very low on the engine and is driven by a single grove 'V belt, which at the time would have been an absolute PITA to try and get functioning correctly with the 2j. I must admit I did not try and physically fit the BMW pump in the Toyota location as it was in the 'too hard' basket.

I am fairly certain the extra bay temps are due to the engine fitment and inability for heat to disperse. BMW don't run an undertray from factory under the bay in the E32's from what I can see, so no joy in that avenue. I doubt this would help with static/idle temps anwyays.

[GTSBoy]

Set up a water spray onto the PS reservoir that you can turn on when you're half way through the sort of sit in traffic situation that would cause it to shit itself. See if that helps.

[10sec rx7]

how hard is it to change to a normal vacuum booster??