This is about 99 Volvo S40 MKI Petrol Car(2.0L 136hp).
Couple months back, I noticed a small leak on one of the power steering hoses. It was really small one and power steering fluid wasn't decreased at all. I'm regular checking fluid levels.

However recently I'm hearing a very smooth winding sound from power steering pump. It is really annoying from inside of the car also. It increases with the engine speed, acceleration and the sound is syncing with the engine speed I guess. When I reach the 5th gear or so it sometimes goes and comes back.

I heard, when some air bubbles are on the PS fuild system, that causes sounds. However I've done a full PS fuild flush recently to get rid of the problem? However still no luck.

How to troubleshoot this?

 

I'm betting the leak and the sound are two different issues. Given it's a 19 year old pump it's probably the bearing starting to fail.

 

Thanks for the response.
Well in that case. Is there any replacement available for bearing only or should i have to go for new whole pump. I looked for any service kit or bearing online, however it seems the all the listings are for used pumps.

 

I have only replaced the whole pump. It would be an interesting exercise to figure out how to press out the old bearing and press in a new one. Assuming I could find a matching bearing. However, I wouldn't replace the pump only on my internet advice. First make sure you have Volvo compatible power steering fluid. The wrong fluid will make it whine too. My daughter's Honda made noises like a failing pump until we replaced the fluid with Honda approved fluid. Personally I wouldn't replace the pump until it failed completely. But that's just me as the car doesn't make long trips far away from help.

 

Great content. So according to my research on this topic, the sound can be caused due to the.

- Un-Even tire pressure
- Bad fluid
- leaks on hoses
- Air bubbles in system
- Finally Bad Pump

I'm about to fix and see first four reasons. What would be the Volvo compatible PSF would be? My manual says just use ATF. Is there any particular brand or additive?

 

Just ATF as the manual states. You don't want to use Power Steering Fluid if the manual calls for ATF.