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power steering intermittently stiff

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Danny Wilde
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power steering intermittently stiff

Post by Danny Wilde » Wed Jul 22, 2015 4:17 pm

Hi guys! Every now and then I can feel the power steering getting stiff in very short intervals, what would be your diagnose?
Thanks for your help :D
Danny
9/1986 euro 635CSi manual Diamantschwarz

ron
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Post by ron » Wed Jul 22, 2015 4:19 pm

Belt damp and slipping.
They are ALWAYS rustier than you thought!!!!!!
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Brucey
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Post by Brucey » Wed Jul 22, 2015 4:35 pm

yep, that'd be my guess too.

If the pump loses pressure for other reasons, there is normally a noise of some kind or other, but if the belt slips, it can do so almost silently.

cheers
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Da_Hose
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Post by Da_Hose » Wed Jul 22, 2015 6:55 pm

Replace the belt and wash the pulley surfaces with acetone. Confirm you have enough PS fluid.

If that doesn't do it, then you probably have a pump issue.

I had the same thing going on, plus some pump groaning. Replaced the pump and the issue is resolved.

Jose
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Danny Wilde
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Post by Danny Wilde » Wed Jul 22, 2015 7:09 pm

Dear Brucey, Ron and Da Hose, thanks for your prompt reply!!
Will check accordingly to your suggestions. As a matter of fact I forgot to say that I also hear some noise only when I reach both right and left limits of the steering, just wondering if this is normal....
thanks again :D
9/1986 euro 635CSi manual Diamantschwarz

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Da_Hose
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Post by Da_Hose » Thu Jul 23, 2015 9:46 pm

Some noise at the stops is normal. Lots of grumbling when sitting or during range of motion could indicate issues.

Jose
1987 M6 - My dream car

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Danny Wilde
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Post by Danny Wilde » Thu Jul 23, 2015 9:53 pm

Da_Hose wrote:Some noise at the stops is normal. Lots of grumbling when sitting or during range of motion could indicate issues.

Jose
thanks Da Hose, glad at least that is normal, will check what suggested above and post updates! :D
9/1986 euro 635CSi manual Diamantschwarz

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Danny Wilde
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Post by Danny Wilde » Sun Aug 09, 2015 11:51 am

Hi guys,

there is a little change in the symptoms, no intermittent stiffening anymore, but a constant slight stiffening of the steering all the time, at warm engine, like the PS is helping roughly 20/30% less of how it normally should…

As suggested by you I just checked the belt, it's quite new, forgot that I got it replaced 3 years ago along with the others, it's correctly tense and clean so no slipping there.
Then checked the reservoir which I think has been serviced last year during the last servicing, I thought I'd find it empty at cold engine but it actually was full already (see pic below). Is this normal? I thought I should have found it empty on cold and should have pumped the brakes in order to get it filled and check levels right? :-?

My dealer's just gone on holiday and I'm about to leave for a trip with my beloved 6er and was wondering if this problem might escalate in a totally undriveable situation :shock: or just stay as a little heavy steering issue… Any guesses?

Thanks for you help..
D :D
Attachments
PS reservoir status at cold engine.JPG
PS reservoir status at cold engine.JPG (185.6 KiB) Viewed 2453 times
9/1986 euro 635CSi manual Diamantschwarz

m6dave
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Post by m6dave » Sun Aug 09, 2015 12:15 pm

You are correct the reservoir level should be below the screen unless you pump the brake pedal about 10 times, suggest checking the "bomb". Start the engine then stop the engine and apply the brakes, as you release the brake pedal you should hear the sound of the hydraulic fluid leaving the booster, repeat this several times and listen until the noise changes, should be about 10 times. If possible have an assistant watching the fluid level in the reservoir, it should rise with each brake application and release.

If this is not as expected you can test the bladder in the bomb by removing it and measuring the depth in the hole in the top.

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Brucey
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Post by Brucey » Sun Aug 09, 2015 3:43 pm

if you leave the car overnight any small leak in the system's valves (which is quite normal) will cause the reservoir to fill itself as you describe. The only time the reservoir should definitely be low on oil is immediately after the engine is run. If it is, and the reservoir refills when the brake pedal is pumped 9 times out of 10 the 'bomb' is fine; no need to eff about testing stuff that doesn't need testing, if the bomb is bad the brakes will be crap too, and you will know all about it.

The PAS will go stiff anytime there is momentarily no pressure at the pump outlet.

Possible causes of this are

- slipping belt (are you absolutely sure it is the right belt and the tension is correct???)
- tiny hole on feed hose to pump (also makes noise)
- clogged filter in reservoir base
- failing pump
- failing pressure relief valve on pump
-failing pressure regulation in valve block

however the steering will also go tits up if

- there is a fault in the steering box servo
- a failing high pressure hose
- failing steering box bracket on subframe
- something mechanically jamming the steering mechanism.

I certainly wouldn't go on a road trip until I'd eliminated some of these because they could be real show-stoppers or even cause a nasty accident (of the 'going straight on like it or not on mountain road') variety.

cheers
~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

rhanley 635csi89
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brake bomb

Post by rhanley 635csi89 » Sun Aug 09, 2015 5:13 pm

Good info at this link.

Brake Bomb replacement

http://home.insightbb.com/~todd.kenyon/bomb.htm
89 635CSiA (11/88 build)
AlpineWeiss II (218)/Natur(0200)
87 L6 635CSI Sold
87 MB 560SL

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Danny Wilde
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Post by Danny Wilde » Thu Aug 13, 2015 10:56 am

Brucey wrote:if you leave the car overnight any small leak in the system's valves (which is quite normal) will cause the reservoir to fill itself as you describe. The only time the reservoir should definitely be low on oil is immediately after the engine is run. If it is, and the reservoir refills when the brake pedal is pumped 9 times out of 10 the 'bomb' is fine; no need to eff about testing stuff that doesn't need testing, if the bomb is bad the brakes will be crap too, and you will know all about it.

The PAS will go stiff anytime there is momentarily no pressure at the pump outlet.

Possible causes of this are

- slipping belt (are you absolutely sure it is the right belt and the tension is correct???)
- tiny hole on feed hose to pump (also makes noise)
- clogged filter in reservoir base
- failing pump
- failing pressure relief valve on pump
-failing pressure regulation in valve block

however the steering will also go tits up if

- there is a fault in the steering box servo
- a failing high pressure hose
- failing steering box bracket on subframe
- something mechanically jamming the steering mechanism.

I certainly wouldn't go on a road trip until I'd eliminated some of these because they could be real show-stoppers or even cause a nasty accident (of the 'going straight on like it or not on mountain road') variety.

cheers
Brucey! thanks for going to the trouble of such a detailed answer! Will check them out :D

rhanley 635csi89 and m6dave thank you too!

best
D
9/1986 euro 635CSi manual Diamantschwarz

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miklilmag
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Post by miklilmag » Thu Aug 20, 2015 12:15 pm

Hello, not clearly mentioned yet, Brucey does have it on the list, and it sounds like the culprit!
There is a filter on bottom in reservior, the fluid will be restricted in flow if clogged and give you steering problems, if not working properly it will effect the brake bomb and the mastercylinder, needs to be changed!

Franke

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Re: power steering intermittently stiff

Post by maestro84 » Mon Jun 04, 2018 10:01 am

Hello. I bought a '83 635 to fully restore. Everything was taken off the car. After assembly the steering feels very heavy all the time. The car is not ready yet but i tried the cars breaking and cornering ability slowly in my yard. The steering unit was taken apart (and set with friction meter correctly) as well as the power steering pump. The filter in the reservoir was not changed. Belt is new and tight.
I filled the fluid reservoir and followed the steps of the filling and bleeding procedure. Everything seemed fine (except the following: the system had take 2 liters of fluid but it took 1,8) until i tested the steering. Very stiff.
I tested the bomb. With engine off i pressed the pedal 20 times and started the car. No drop in fluid level. Can it be the filter from the reservoir maybe anything else or definetly the bomb went wrong?
I thought something is overtightend but i checked all the torques before tightening so i think its not the case.

maestro84
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Re: power steering intermittently stiff

Post by maestro84 » Sat Jun 09, 2018 7:46 pm

Little update.
I took off the pump it had too much play, problem solved. This time the bleeding was much better, lot of air came out from the system. Now i have power assist only when i turn the wheel right. Wtf. :x
When car is on the ground and engine off: left and right turns feel the same.
On stands, engine running: as above
On the ground, engine running: stiff left, easy right
When the car is rolling its better, but a slow sharp left turn is almost impossible with two hands.

I disconnected the steering gear from the steering system but left the hoses on. With the engine running left turns felt harder. Removed the hoses, moved the lever left and right i felt not much difference.

Anybody experienced this problem? [-o<

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Danny Wilde
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Re: power steering intermittently stiff

Post by Danny Wilde » Wed Jun 13, 2018 7:38 pm

Hi maestro84! My issue with the intermittent stiffness of the steering (back in 2015) was fixed by replacing the seal between the steering column and the steering box, and by replacing the low pressure hose of the power steering, hope this might be useful info for you :-)
good luck :-)
9/1986 euro 635CSi manual Diamantschwarz

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Brucey
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Re: power steering intermittently stiff

Post by Brucey » Thu Jun 28, 2018 9:08 pm

maestro84 wrote:
Sat Jun 09, 2018 7:46 pm
Little update.
I took off the pump it had too much play, problem solved. This time the bleeding was much better, lot of air came out from the system. Now i have power assist only when i turn the wheel right. Wtf. :x
When car is on the ground and engine off: left and right turns feel the same.
On stands, engine running: as above
On the ground, engine running: stiff left, easy right
When the car is rolling its better, but a slow sharp left turn is almost impossible with two hands.

I disconnected the steering gear from the steering system but left the hoses on. With the engine running left turns felt harder. Removed the hoses, moved the lever left and right i felt not much difference.

Anybody experienced this problem? [-o<
it sounds like you have a fault that means that the servo doesn't work correctly when the steering is turned one way. IIRC there are separate fluid passages, valves etc inside the steering box for each direction.

It might be that the fault has arisien because some debris has entered the PAS box. A failing hose could have created such debris.

I think it is possible to overhaul the PAS box but it might be a job best left to a specialist. If you can get hold of a spare PAS box then this would be an easy thing to try, but if something in the system is generating debris then this may not represent a permanent solution.

cheers
~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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Jono B good
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Re: power steering intermittently stiff

Post by Jono B good » Thu Jul 19, 2018 6:40 pm

Have the proper tire inflations been correct? Sometimes it's the simple things that get over looked too.
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