Oil in Strut Tubes?

[z boy mn]

Good morning everyone. I'm replacing my front shocks during a suspension refresh, and I noticed the previous owner filled the strut towers with oil when I took them apart. When I talked to MSA (which is where I got the new shocks), they said this was an "old school" practice to reduce noise and sticking.

I'm not crazy about filling the struts with oil as it seems it could leak all over the place, including all over the brake rotors--which would be bad.

So, does anyone have any advice on this practice? If the oil is meant for rust protection, I was thinking maybe I could just coat the shock body in a light oil/grease...or maybe just use anti-sieze instead.

Hoping someone can help!

[Jeff G 78]

It's for cooling.  Dampers get very hot and the oil conducts the heat out to the tubes much better than air.  The oil will not leak out, so don't worry about that.

[z boy mn]

Ahh, that makes sense, Jeff. Thanks!

Any idea how much oil to put in? I'm assuming I should put the shock in first and then add the oil. When the oil gets hot, it'll expand, correct? So, I don't want to fill it to the top when it's cold. Or maybe there's a way to account for this?

Also, I noticed that the shocks I'm replacing (Tokico Illuminas) also have a washer between them and the nut on top. The new ones don't come with a washer, so I'm not sure if that washer is part of the car, or simply what was needed to make the Tokicos fit properly. Are you familiar with this, too?

[Jeff G 78]

Add enough oil that the cavity is mostly full - it doesn't take much!  You can leave an inch or so of air at the top, but I have never had a problem with the oil expanding and puking out.

I have Illuminas in my 280 and they didn't have a washer, but it all depends on the amount of room you have.  When you insert the cartridge and screw on the gland nut, it should tighten down on the cartridge before it runs out of threads on the housing.  The washer was likely added because the gland nut didn't clamp the cartridge, but rather just tightened onto the housing or ran out of threads.  Make sure the cartridge cannot move up and down prior to it bottoming out and then finish tightening it.

[z boy mn]

That makes sense, Jeff, I'll try that and keep the washer handy in case I need it. I can understand why you don't want the shock rattling around on the inside of the strut.

Thanks again!

[SteveJ]

Another reason for the oil is that it will keep the strut from rusting to the tube. 

Overfilling isn't too big of an issue, though the tire shop had thought I had blown a front strut when I got my last tire change since some of the oil was still on the outside of the strut tube.

By the way, @zcardepot.com is now selling an octagonal wrench to remove the gland nuts. It's good to support companies that come out with new products to support our hobby.

[z boy mn]

Thanks for the heads up on the wrench, Steve, I will look into that! Also, I'll be careful with the oil and I like the idea of being able to remove the shocks in the future rather than have them rust to the strut.

[z boy mn]

Just a note here...

I checked the FSM and it recommended oil in the strut tubes as well. It even gave the quantity (290cc).

BUT, I went to the KYB website and they suggest absolutely no oil. The website is here:

https://www.kyb.com/knowledge-center/shock-tech-for-pros/installation-tips/strut-cartridge-installation/

I've got an email in to KYB's technical support to confirm their recommendation. My guess is that their assertion is that the quality of the shocks has changed over the last 47 years. I'll reply again if they recommend something different.

As for what I'm going to do, I'm not sure yet. My gut tells me to go with the manufacturer of the part.

Edited March 15, 2018 by z boy mn

[Dave WM]

fsm is not for cartridges. That oil was for actual damping. I just replaced the oil and put new o rings since all the internal parts were intact. the original design was rebuildable.

Edited March 15, 2018 by Dave WM

[240260280]

Maybe the new KYB seals' material now break down in oil.

 

As mentioned above, oil helps transfer heat and stop rust.

[Patcon]

22 hours ago, 240260280 said:

Maybe the new KYB seals' material now break down in oil.

 

As mentioned above, oil helps transfer heat and stop rust.

I wondered if a seal issue is the reason too. If it is, you could add less oil so the bottom of the strut couldn't bond itself to the tube but the oil level would never get near the top strut seals

[z boy mn]

Good thinking...

I did receive an email from the KYB technical support yesterday, and they -- in emphatic terms -- said that I shouldn't add any fluid to the strut tubes. They also wanted all previous fluids drained and the strut tubes cleaned out of residuals. So, I'm thinking there must be another issue (like you have mentioned regarding seals). I drained the tubes, washed them out with brake cleaner, and wiped them out with a rag. The car is stored inside and never sees winter, so I'm not that concerned about lots of rust, but I sure don't want the shocks to become stuck in there. I'll see how they fit when the arrived today and make a decision. Next time I pull them out, or take off the suspension, I'll dig up this post and do an update (hopefully with good news!)!