TomiK

Hi guys.

Fairly new member here but hoping to contribute as I do all maintenance on my 2008 Boxster S myself (friends think am crazy!).

Anyway, I replaced my crank pulley with the RSS underdrive unit to quieten things down a bit and get the car ready for a track day. At the same time, I removed the idler pulleys and noticed that the upper idler pulley (aka deflection pulley) was noisy when I shook it (holding it real tight). Sounded like loose bits inside. The bearing was fine/smooth so am not too worried. Just wanted to know if this can be considered normal. The other one made no such noise.

Also, the steering pump pulley rattles when rotating it back and forth - appears that one user believes this is normal (caused by gears inside moving). I also notice that the steering pump whines a bit when turning the steering wheel - is this definitely a sign of impending PS pump failure? Should it be silent?

Any thoughts would be appreciated.

Tomi

Macster

It has been a long time since I have fondled the idler rollers on my Boxster or a set of new ones but I seem to recall they had a bit of wobble to them. The ones on the Boxster are original but I have had two idlers rollers go bad on the Turbo's engine and in both cases the bad idler roller bearing made noise when the engine was running. I do not know what the bad idlers felt like as I didn't bother to check their feel. I think I have then still somewhere…

If the idler rollers are quiet when the engine is running I'd hazard a guess they are ok. If in doubt you can replace them. IIRC, they are not that expensive. It is part of the cost of tracking.

IIRC when I had the serpentine belt off of my Boxster's engine -- when trouble shooting a rumble that proved to be a bad water pump -- I seem to recall the power steering pump rattled a bit when I rapidly turned its pulley left and then right. I do not think the pump is a gear pump but a sliding vane pump, but the noise is normal. There should be no axial or radial play in the pulley/shaft of the power steering pump. There should be no signs of any leaks from where the shaft goes into the pump housing and the lines and their connectors at the pump should be dry.

The power steering pump is generating no little hydraulic pressure when the engine is running. When the wheel is turned this opens a valve on one side of the rack to direct high pressure fluid to that side of the rack and closes the valve of high pressure fluid to the other side of the rack. This valve though remains open to allow low pressure fluid to escape from this side of the rack as the piston moves towards that side as the wheel is turned.

As the wheel is turned the high pressure fluid is directed to the side of the rack so this fluid pushes on the piston in the rack and assists in forcing the rack in the proper direction so the car turns in the direction desired by the driver. The further the wheel is turned the more fluid is required and the pump is having to supply this fluid under pressure.

That the pump makes a bit more noise when doing this is normal.

As an aside, I make it a habit to avoid leaving the wheel turned sharply with the engine running to avoid putting extra strain on the pump.

Be sure the pump fluid level is correct and doesn't change.

There can be a failure in which a high pressure valve fails and directs too high of a pressure fluid to the rack. This forces fluid out past the rack seals and because this fluid is captured by the rack dust boots there will be no signs of a leak.

Initially the only clue something is amiss is the fluid level drops. But this is often not checked regularly and the pump runs low on fluid.

As the power steering fluid level drops this can and will result in damage to the pump. If this is allowed to go on too long -- and I have no idea how long is too long -- the pump, the rack and the line with the bad valve have to be replaced.

Last but not least I fail to understand why anyone would want to slow down his engine's water pump.

Try this simple experiment. Get a pan with a flat bottom and put about an inch of water in the pan. Put the pan on the stove and turn on the burner.

Watch the pan. After awhile you will see bubbles start to form on the bottom of the pan. Lift the pan and gently swirl the water in the pan about. This action removes the bubbles. Allow the pan and water to get hotter. The bubbles from faster and are larger and require more energetic swirling to dislodge.

Where those bubbles remain is where localized overheating would occur.

By installing an under drive pulley you reduce the flow rate of the coolant pver the hot surfaces of the cooling passages. This can allow bubbles to form and these can coalesce into pockets of steam which block coolant flow over the areas they form. This leads to localized overheating which ain't good.

TomiK

Thanks Macster - I appreciate your comments (and those from your other posts - always enlightening).

The pulley is not so cheap in South Africa (crappy exchange rate at the moment) but I will probably replace it nonetheless. It's hard to tell which engine bay noises are normal as I have only ever driven this car and a friend's Cayman S.

Thanks for the detail on the P/S pump. It does whine a bit but the fluid level hasn't changed so I'm happy to just keep an eye out on the fluid level (the engine cover is easy enough to remove) and ignore the whine for now. I also try avoid full lock positions for that same reason.

On the underdrive pulley, I hear what you're saying - will do some more research into it. Again, it's easy enough to put back to stock.

Thanks again.
Tomi

TomiK

Update to this: On closer inspection, the idler pulley bearings were actually shot. They spun fine without load but were likely dry and worn out (hence the rattle). So I bought two replacements from the dealer. Hopefully this will quieten things down a bit.

On the power steering 'problem', I noticed that when I turn to full lock and release (with the engine running), the revs will increase for a second (upon release) before settling back to a normal idle. Does anyone know if a faulty P/S pump would cause engine rev's to fluctuate?

Macster

Power steering pump failures are rather rare. Ignoring infant death failures which would be covered under warranty it seems about the only ones that fail do so when the vehicle is tracked.

The techs I consult with tell me that generally when a power steering pump is replaced it is replaced because it is noisy. (Same goes for transmissions, differentials, etc.)

If you tell me the pump is quiet, the fluid level is good and not dropping, then I would have to offer the opinion that I do not think your car's power steering pump is bad.

My WAG would be the momentary revs increase when bringing the steering wheel back from full lock is due to the sudden drop in parasitic load represented by the power steering pump. This sudden drop in load has the engine rev briefly until the e-throttle can react.

This load is considerable. It is this load that has driven Porsche (among other car makers) to replace the hydraulic power steering system with an electro-mechanical one.

It occurred to me one might be able to see how much load this is by connecting an OBD2 code reader/data viewer to the car's OBD2 connector and configure the device to monitor engine load in real time then turn the wheel to full lock and then turn it back straight again -- do not let the wheel linger at full lock -- and note the load readings during this process.