steering and suspension Bilstein Oil Question

[Dake]

My 02 has a known history of sitting. I decided to take the suspension apart to make sure everything was sound, and when I pulled the shocks out of the strut housings there was oil an inch deep coating the bottom of the shock. When I opened the shocks, exposing the bump stops, they had what seemed to me like a whole lot of oil inside. I have read that motorcycle fork oil is okay to use, so I'll be refilling them with that. I would think too much oil would cause issues (hydrolocking?).

 

Is there a level to go by when filling the shock tube?

 

Will oil continue to escape and pool in the strut housing?

 

Why can't I just grease the shock insert instead of using oil?

Edited April 16, 2015 by Dake

[Mike Self]

The oil you found probably didn't come from the current Bilstein inserts, but was left over from the original front shocks which used the strut tube as its outer housing.  When the OEM shocks went bad, the replacement parts were inserts--Bilstein, Sachs, KYB etc.  Many people left the old shock oil in the strut to help with heat transfer from the insert (which isn't in the air stream as it's inside the strut tube) to the outer tube and thus to the air.  Oil transfers heat better than air.

 

You can leave the old oil in or drain it--your call.  My Bilsteins now have over 140k miles on 'em and I installed 'em dry; others will swear by adding oil for cooling--and that would probably be helpful if you're tracking the car.

 

cheers

mike

[Dake]

Okay. Thanks for the info. I will probably use some oil. When I disassembled the shock itself, removing the yellow housing, there was a whole lot of oil inside there as well. You're saying that's probably just oil that found its way in from someone having filled the shock tower? Or is that supposed to be there?

Edited April 16, 2015 by Dake

[Mike Self]

Dake, re-read my message--it could have been the leftover oil from the OEM shock that the PO didn't drain (siphon) out when he installed the Bilsteins, or just oil he poured in for the aforementioned heat transfer.  Doesn't really matter; so long as it isn't cooking oil you're OK...and if the Bilsteins were leaking, you'd know it--the gas pressure would be gone and there would be no resistance when compressing.

 

mike

[TobyB]

 

 

 When I opened the shocks, exposing the bump stops, 

uhh, picture time....

 

So we have the strut- has a tube, a spring perch welded to one end, and a spindle on the other.

 

We then have a strut insert which is the damper part of the equation.  This, you could call a shock.

Fits inside the strut. Bilsteins typically- but not always- have the bump stops inside the insert, which is 

why I'm wondering if you took the insert itself apart.

 

Did you open the insert and find a lot of oil?  'Cause if you did, and it didn't go 'pssshhhhttttt' and spray

oil all over, it was shot.  If it DID go psshhtttt then it's shot now, and should be re- pressurized.

 

If you DIDN'T have an insert, but a smaller tube that rode inside the strut, you have Boges, not Bilsteins, and they're

OEM.  And probably shot, too.  I've taken apart several dozen struts, and so far have only found one of the OEM 'wet' dampers.

It was cool...

 

But a pic would help, in this case...

 

On Bilstein inserts, the outer body's just a housing, so a bit of oil- or, yes, grease would be fine, and maybe be better at resisting water-

is all it takes to keep the insert from rusting to the strut housing.

On other types of damper (Konis, KYB, etc, anything with a smaller chrome shaft sticking out) some oil in there is good to help 

cool off the body of the insert by transmitting heat from the shock body to the strut itself.

 

hth

 

t

[Dake]

It's a Bilstein. Sorry, my wording might be a source of confusion. When I removed the entire shock from the strut tube, there was oil at the bottom. This was the case for both front shocks. When I removed the yellow cover to expose the bump stops of the shocks (NOT depressurizing them, the pressure chamber is sealed and not breached and the shocks work fine) the right side had a ton of oil in it while the left side only had some. My question is whether there is supposed to be ANY oil in the strut tube or ANY oil inside of the yellow cover, where the internal bump stops are. If there is, it probably shouldn't look this bad.

 

In my mind if the oil inside the yellow cover didn't get out of the way fast enough when the shock compressed, the system could hydro-lock.

Also there is what appears to be a burn mark on the yellow cover of the left side shock. Not sure where that could've come from.

[Dake]

Also can anyone confirm whether there's supposed to be an o-ring / seal at this location?

[wegweiser]

Time for new strut inserts. Those are now toast. Not to be disassembled by end user. :/ 

Edited April 18, 2015 by wegweiser

[Dake]

I've never heard that advised before. I've also never heard of problems after reassembly. Not to say I won't take your word for it 

 

Motorcycle forks can be disassembled and reassembled fully with no issues, I don't see why these would be any different, except the pressure chamber of course.

Edited April 18, 2015 by Dake

[TobyB]

Well lookee there- there IS a bumpy stoppy in there!  I wondered...

 

No, typically those don't come that far apart.  I didn't think they could.

BUT if the cartridge is still gas- charged, you should be able to put it back together.

And yes, there should be an o ring or some kind of seal in that groove.

 

Yes, you're spot- on- they can hydro- lock with too much liquid in the bottom.

I've had them fill with water from a failing top- seal and lock at regular ride height.

It's not a great design, in my opinion, for a street car.  Yes, it saves a little unsprung

weight, but at the expense of higher overall weight and critically, a smaller, harder-

to- cool tube.  

But I also think they work great, and while I've had numerous Koni failures now,

in 18 years and at least a dozen dampers from different beat- up parts cars, 

I have seen NO failed Bilsteins.  Including those on my pickup.

 

t

[Dake]

The car sat as-is in the PO's garage for over a year, and before that for "5-8 years" as-is in a yard in New Mexico. That probably played a part. Hardly any rust, but a lot of spiderwebs to dust off.

 

Thanks for the info! I'll be careful with re-assembly. Still not 100% sure if there's supposed to be oil INSIDE the yellow tube to begin with, or if that made its way in when the bottom seal failed.

Edited April 18, 2015 by Dake

[TobyB]

No, it's supposed to be dry inside the cover that hides the bump stop.   Or just oily enough to prevent rust...

 

t

[Dake]

Thank you! Notes have been taken.