Recent Topics
Amsoil Euro 5W-40 92Benz 190E 2.3L 8V 3889 miles
by IllinoisSparky
Today at 09:11 PM
Which oil?
by SEMI_287
Today at 09:05 PM
Fluid change on my 2015 Accord
by dan_erickson
Today at 08:56 PM
Upgrading brakes
by ram_man
Today at 08:49 PM
Rear end sounds like an airplane
by mclasser
Today at 07:49 PM
GDI engine's and motor oils
by gabriel9766
Today at 07:42 PM
Old toyota Need shocks?
by ceast
Today at 07:27 PM
How to do a clean install
by Oldmoparguy1
Today at 07:21 PM
Troy Bilt Pony
by OSUFan86
Today at 06:43 PM
$1.33 for a GALLON of 87!
by Vern_in_IL
Today at 06:30 PM
Eating out, beware you all
by CourierDriver
Today at 06:13 PM
Best Sponge For Washing Cars
by George7941
Today at 06:08 PM
Newest Members
threeeightteen, TOADchunks, Longo9596, Roadrunner77z, rp5677
56888 Registered Users
Who's Online
95 registered (AZjeff, 69GTX, bdcardinal, 901Memphis, 74DartSport, 2015_PSD, 5 invisible), 1239 Guests and 214 Spiders online.
Key: Admin, Global Mod, Mod
Forum Stats
56888 Members
66 Forums
244530 Topics
3982395 Posts

Max Online: 2862 @ 07/07/14 03:10 PM
Donate to BITOG
Topic Options
#3286422 - 02/18/14 04:49 PM Shock Absorber Article
ronbo Offline


Registered: 04/04/07
Posts: 796
Loc: western ny, usa
Interesting about the three valves, courtesy of ROCKAUTO newsletter. cut/paste as follows,

"What about oil leaks? Shock absorbers and struts contain hydraulic oil. Truly ancient hydraulic seals made from materials now considered inferior might have “dried out” or otherwise lost their ability to seal over time, but Monroe shocks were made with modern seals even in the 1990s. These new/old Monroe shocks do not have any oil leaks. The mounting bushings also look identical to any more recently manufactured new bushings.

What about gas leaks? A “gas” shock or strut usually has nitrogen gas in the oil reservoir. A gas shock is not the same thing as an air shock. The nitrogen gas is primarily intended to help keep the oil from foaming when the shock cycles rapidly on washboard dirt roads or at high vehicle speeds. If the hydraulic oil foams, then the shock’s damping capacity is reduced. If the shock’s oil reservoir is not leaking oil then it probably is not leaking nitrogen gas either. One of the reasons nitrogen is now used to pump up tires is that nitrogen molecules are larger and less prone to leaking than oxygen and other components of air. Ambient “air” is 78% nitrogen, so there is no strong chemistry working to force the nitrogen out of the shock’s oil reservoir.

Even shocks that have been driven way beyond the 50,000-mile mark over many years usually do not fail because of oil or gas leaks. Modern shocks use multistage oil valves. Each valve is a calibrated metal disk that flexes to let oil flow through in response to different road conditions. The first stage valve opens in response to little bumps, the second stage valve opens in response to medium sized bumps and the third stage valve opens in response to big bumps. These valves are usually what wear out first. The metal valves fatigue and go limp after millions of openings. The first stage valve is the first to die because the vehicle is constantly exposed to little bumps and the valve is constantly cycling.

Multistage valves are one reason the old push-down-on-the-fender test for shocks is now almost useless. If the car keeps bouncing after a big push down on the fender, then that means the third stage, big-bump, valve is now worn out, the second stage valve has been worn out for awhile and the first stage valve has been worn out for a really long time. A shock that fails the fender-push test should have been replaced long ago. That shock absorber or strut has not been protecting the vehicle’s suspension parts and assisting with safe vehicle handling and braking.

Time will tell, but I bet I will continue to be very happy with the new, fifteen-year-old shocks on my thirty-year-old 300. We will see what my son, the handling expert, says the next time I let him behind the Chrysler’s wheel!

Tom Taylor,
RockAuto.com

Top
#3286438 - 02/18/14 05:06 PM Re: Shock Absorber Article [Re: ronbo]
NMBurb02 Offline


Registered: 09/12/12
Posts: 1853
Loc: Crowntown, CA
Interesting. Thanks for posting. I get the newsletter emails, but do not often read the newsletters.
_________________________
2002 Chevy Suburban 1500, G-Oil 5W-30, Fram TG3675
2006 Pontiac Grand Prix GT, M1 0W-40, Fram TG3387A

Top
#3286480 - 02/18/14 05:34 PM Re: Shock Absorber Article [Re: ronbo]
Wilhelm_D Offline


Registered: 01/28/09
Posts: 818
Loc: Tacoma, WA
Originally Posted By: ronbo
What about gas leaks? A “gas” shock or strut usually has nitrogen gas in the oil reservoir. A gas shock is not the same thing as an air shock. The nitrogen gas is primarily intended to help keep the oil from foaming when the shock cycles rapidly on washboard dirt roads or at high vehicle speeds. If the hydraulic oil foams, then the shock’s damping capacity is reduced. If the shock’s oil reservoir is not leaking oil then it probably is not leaking nitrogen gas either.

This is only true of low pressure double tube shocks and strut.

A monotube with nitrogen gas is entirely different matter.

Top
#3286493 - 02/18/14 05:47 PM Re: Shock Absorber Article [Re: ronbo]
nwjones18 Offline


Registered: 11/30/09
Posts: 724
Loc: Warner Robins, GA
I had read this article before buying some wholesale closeout Motorcraft shocks for my Bronco. Boxes indicated the shocks were built in the late 90's and They have been giving me good service so far. It has 6 shocks and I didn't pay over $22 a piece for any of them.


Edited by nwjones18 (02/18/14 05:48 PM)
_________________________
1988 F-150. 4.9 I6 244k. 10w-40 Castrol Syn-blend Motorcraft FL1A.
2005 Cadillac STS N* 100k. 5w-30 Castrol Syn-blend PureOne

Top