Shock Absorber Fluid Replacement

Bob Bidonde

Bob Bidonde

Well-known member
The restored shock absorbers on my Victoria are filled with glycerin just as they were originally by Houdaille. My goal is to replace the glycerin with transmission fluid to prevent internal rusting. It was my hope that transmission fluid is soluble in the glycerin so I coluld avoid removing the shocks to drain the glycerin, but that is not the case. In a test 50-50 combination by volume, the transmission fluid sits atop of the glycerin with no mixing.

So do not attempt to mix glycerin and transmission fluid.
 
Bob. Glycerine is a water-soluble liquid unlike oil, which is hydrophobic or water-hateing.
Soluble oils will mix with glycerine, but I am not sure how well that mix would perform in an Houdaille shock. It is an interesting thought that had never occurred to me.
The ratios of glycerine and soluble oil that will stay mixed might vary with the brand of oil used but the legacy of corrosion that glycerine creates as it sucks up water from the atmosphere would be greatly reduced if not eliminated.
I will try this when I get back to my laboratory from the far North Car Rally I am on.
Soluble oil of any viscosity can be created from the appropriate oil and surfactant combination. So a lubricant much thicker than conventional cutting oil could be made for worn shocks.
SAJ IN NZ
 
If the shocks are still new enough then maybe the cover will still be able to spin loose allowing for the fluid to be drained. If not then it seems they may have to come off.
I'm kinda surprised they have glycerine in them, it was used for just a short time before the change.
 
John is spot on
Are you sure it is glycerine? Have you checked with the restorer or did you do then yourself and know for sure? I used to rebuild shocks and never used glycerine ; always petro based. Usually jack oil. If the were a little lacking pressure I stepped up viscosity
If they aren’t leaking now, taking them apart will put that blessing in jeopardy!
 
My shocks were restored by Robert Paul of Yoder, Colorado and they are filled with glycerin. The purpose of this post is a warning not mix a petroleum product with glycerin. Because of its availability, I am refilling my Houdailles with automatic transmission oil.
 
Understood
But are you cognizant of what John said about emptying the shocks?
The inner chamber will not readily drain
 
Robert Paul restored my shocks, as well. Once, in a rare telephone call (he was hard to get a hold of), he told me not to mix oil with glycerin. Also he said you could not get all the oil out of the truck without taking it apart. Someday I will continue the interview with Robert… When I get to heaven too.
 
Just for fun!
 

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This is somewhat of a departure from the original conversation, but pertains to shock fluid. I recently acquired a completely restored running chassis with restored shocks. Two of the shocks are leaking fluid and I’m not experienced enough to tell what type of fluid was used in the restoration. Unfortunately the individual who performed the work is no longer around so I need to either diagnose what the oil type is so I can keep the shocks topped off, or find a suitable fluid that will mix regardless of what he used. The drops beneath the leaking shocks seems to be an oil, and is somewhat thick and sticky. Any suggestions?
 
Dead right OldBlue. Glycerine also has an incredibly sweet taste. The water test is safer though!
SAJ in NZ
 
It you find really old castor oil you will likely be able to tell by the smell. When it goes bad, it doesn't smell good. Mineral oil generally always smells the same like most mineral oils do. Glycerin does taste sweet. I still use it for internal mount sores. If it gets all brown and nasty looking then most folks wouldn't want to taste it.

Glycerin and castor oil will both go bad over time. Back in they day, a who die damper was inexpensive so folks would chuck them and buy new ones. By the time the cars were well worn, a lot of them had lost their dampers into the dustbin of history. They weren't really supposed to be rebuilt. Hell they didn't even have interchangable parts. Houdaille fit each and every one of them individually back in the early Ford era.
 
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Thanks for the good advice, it looks like the fluid leak is oil, so what is the best oil to replenish?
 
I’d use hyd jack oil
But I think I would assess/fix the leaks first
They generally don’t mend themselves
 
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