1999 S70 GLT Power Steering Foam - cause - missing return baffle in pump reservoir

[800artfreed]

Recently on a trip up to Canada and very cold temperatures the power steering system started to make noise when turning the steering wheel. This is my first 1999 S70-GLT. I have two 1998 70-T5s.

There are a number of differences between the two types of PS systems. The old system you check the fluid while the engine is running. The new system you check with the engine off. If you compare the filler caps and dipsticks the new cap has a substantially longer dip stick.

Unknown to me at the time was the change in PS fluid between the older reservoir mounted on the pump and the newer design mounted next to the coolant expansion tank. I added ATF to what looked like pink foam (ATF) in the reservoir. The foam and noise continued. BTW my PS system does not currently have any leaks. When removing the cap from the reservoir a small amount of pressure is released indicating that the system is properly sealed. Still the foam and noise occurred.

Fortunately I have a friend that works at a Volvo dealer and he got me two liters of PS fluid (green, synthetic) that I picked up on my way home from Canada.

I removed as much of the old fluid from the reservoir and filled it with the OEM fluid. After circulating the fluid I removed more from the reservoir and refilled it with more OEM fluid. There was some improvement but after driving at highway speeds the symptoms returned.

Upon reading about purging air from the system I jacked up the car when I got home and cycled the rack from left to right about 20-30 times with the engine off. Some bubbles appeared at the surface of the fluid in the tank then stopped. It looked good. However after driving at highway speeds the foam and noise returned.
The cause of my problem was actually mentioned in another post. You see I could observe the fluid from the return line running into the reservoir. Also there was usually a large bubble or film near the filler opening. This was the result of an important part of the reservoir falling out of position. There is supposed to be an extension from the return line that directs the flow of the fluid at right angles down into the reservoir BELOW the fluid level in the reservoir. Without the extension high flow rates agitates the fluid creating foam that is fed into the pump causing noise.

I was lucky to find another reservoir at the pick and pull. BTW the first one I found was an aftermarket Swedish Parts version. It lacked the cap. When I tried to use a cap from an OEM tank it did not fit! Go figure. I then pulled an OEM tank out of an S80 . After cleaning it with solvent and then rinsing it with OEM PS fluid I installed in the the s70. While at first there was a layer of fine foam on the surface it dissipated rapidly. The pump is quiet too. I need to take it on the highway for a final test.

How can you prevent the diversion extension from falling off? If you remove the return line hose from the tank check to see if the brass tube in the plastic fitting is sticking out. Mine was out 5/8-ths of an inch. I believe that when the flow rate gets high and the amount of brass pipe attached to the diversion extension is less than it should be the PS fluid pushes the extension off the pipe, it falls into the reservoir and our problems begin. I would try to use some channel lock pliers to push the brass pipe back into the reservoir and onto the extension. Hopefully you can avoid the task of replacing your PS tank. I could not get my original extension situated in such a way that I could reattach it. Since it is all black plastic inside the tank I did not take any pictures.
Hope this helps.

[misha]

Air purging from PS pump is done with engine running,filler cap removed and moving steering from side to side untill all air escapes.
Doing that with engine OFF,could damage PS system...if not allready.

Btw....filler cap is also a dipstick which says Add,Cold and Hot....level check when engine OFF,depending on situation....is the engine hot or cold.

[hausmeister]

You see I could observe the fluid from the return line running into the reservoir. Also there was usually a large bubble or film near the filler opening. This was the result of an important part of the reservoir falling out of position. There is supposed to be an extension from the return line that directs the flow of the fluid at right angles down into the reservoir BELOW the fluid level in the reservoir. Without the extension high flow rates agitates the fluid creating foam that is fed into the pump causing noise.

I had the same problem twice... so I can confirm you are not the only one
The black fluid routing part can be hooked with a piece of wire from the bottom of the reservoir (tricky) and pulled up. If you then push the brass tube back in it is fixed again. I had to do this 2 times in 10 years and while it is a bother it is possible without replacing.

[800artfreed]

Thanks for the input. Leaving the wheels on the ground while trying to purge the rack is too difficult if not prone to damaging the system. I had the wheels off the ground when I did my "daily exercise"; turn-turn-turn like the song says. The funny thing is with the diverter in place the air bubbles or foam just seem to disappear on their own. I also think that some owners are using anything they can buy rather than paying $24 dollars per liter from Volvo. The tank I got from the pick n pull looked like it had brown oil of some sort rather then PS fluid. That's why I cleaned it thoroughly.
Doing local driving I have not experienced any foam or bubbles or noise. The system is nice and quiet and the motion of the rack is smooth.

[oragex]

I didn't went through the whole post but a few ideas: the easiest check is a loose hose clamp. In cold weather this can happen. Another thing that can happen is if someone added a 'connector' in the middle of a hose (little probable): the cold fluid will have a restriction at that point and starve the pump until it warms up. Anyhow, most probably you have a slightly loose clamp somewhere that was sucking air.

[Rattnalle]

Never turn the wheels with the car still and on the ground unless on a soft surface. Personally I've just driven slowly while doing end to end turns to get the air out after having the pump or reservoir off.

[Sommerfeldt]

Okay... Did none of you actually read the whole post?

Sorry, OP, I don't know how to prevent that extension from falling off, but if someone would actually read the whole post who has had this problem and have an idea, that would probably help others.

- S

[June]

It's a known fault with the reservoir. All you can do is replace it. On my car power steering oil kept percolating out of the cap, and the pump whine was so aggravating. June

[abscate]

Okay... Did none of you actually read the whole post?

Sorry, OP, I don't know how to prevent that extension from falling off, but if someone would actually read the whole post who has had this problem and have an idea, that would probably help others.

- S

This was the result of an important part of the reservoir falling out of position. There is supposed to be an extension from the return line that directs the flow of the fluid at right angles down into the reservoir BELOW the fluid level in the reservoir. Without the extension high flow rates agitates the fluid creating foam that is fed into the pump causing noise.

Next person who does a PS reservoir swap has to cut it open and take pics!

[Chuck W]

Is there a similar issue on the earlier pump-mounted reservoirs?

I've noticed the same foaming of the PS fluid on the wife's '97 GLT after the RN swap (We kept the old accessories, but swapped racks)

The swap was completed back over the summer, but I've noticed foaming/noise/etc since the weather has gotten colder.