Is my front strut cartridge bad?

[dkad260]

Roughly 10 months ago, I replaced my front strut cartridges with the OE BWI 19420494, also used new coil spring insulators. I had a reputable shop swap the springs and all has been good.



About a month ago I started hearing and feeling a light "thunk" or "bump" in the LF when backing from a stop, sometimes after leaving from a stop, occasionally over light bumps.

I have checked all mounting bolts of the strut, control arms, hub and bearing, tie rod, front diff (case and brackets) front diff brackets are new OE, brake caliper and brackets are tight.

I replaced the front sway bar links today and when I lowered the vehicle, I noticed the LF tire momentarily "stick" when the suspension was loading up...kinda like a pause then release. So I rasied it again and when lowering it did the same. It looks like at a certain point the front strut has a slight "bump" when compressing.

The odd part it this doesn't happen all the time, not 100% repeatable. Could this be the electronic damping mechanism inside? I did make a set of resistors to bypass without a CEL but haven't tried that yet.

There are no odd noises when driving normally or over bumps, suspension is tight. It's the slight movement of the strut from the regular ride height or when it's moved from battery.

All thoughts welcome.

 

[Big Mama]

When you checked the strut bolts did that include the top 3? You mentioned using resistors for non active struts so the auto dampening would be disabled if I understand you right. That system wouldn’t be active with your rig not running. How about your caliper bolts, lug nuts, and wheel bearings? Can you hear anything if you shake the tire? How about the camber bolts? Just throwing stuff out there.

 

[dkad260]

When you checked the strut bolts did that include the top 3? You mentioned using resistors for non active struts so the auto dampening would be disabled if I understand you right. That system wouldn’t be active with your rig not running. How about your caliper bolts, lug nuts, and wheel bearings? Can you hear anything if you shake the tire? How about the camber bolts? Just throwing stuff out there.

All strut bolts are tight, resistors are avail and assembled on a OE pigtail to connect directly to the strut harness if needed for further testing, currently the connection is OE.

Caliper bolts are tight, Timken bearings about 1YO, no movement when moving tire..all is quiet.

You can see the wheel assembly momentarily shake when lowering the vehicle when the strut compresses. It doesn't wobble, but stops then releases again.

 

[Joseph Garcia]

How do the bushings on your upper and lower control arms look? The control arms will move as you lower the truck back onto its suspension.

 

[dkad260]

How do the bushings on your upper and lower control arms look? The control arms will move as you lower the truck back onto its suspension.

Not too bad, just had alignment done and I had the guy check to rule out them moving too much. I will get a pic of them later.

What it seems to do is the strut compresses but stops, then releases. Like moving your finger on a piece of glass..keep it moving it glides, but stop and start again you have to overcome slight friction and your finger momentarily catches...but only in that spot or very narrow range.

In my years of wrenching on vehicles, you would think that there's something in the movement of the control arms causing this binding, but I can't see it.

 

[Joseph Garcia]

Then you may need to remove the entire strut assembly from the truck, and put the entire assembly in a bench press and slowly compress the entire assembly. If you notice that same stop/release issue, then you will know that it is the strut cartridge itself.

 

[petethepug]

A bind like that on a new BWI strut is red flag. No one knows if new, active z55 struts are actually made to operate without power and not destroy themselves. You mentioned “I did make a set of resistors to bypass without a CEL but haven't tried that yet”.

You skipped that part about a suspension DTC / CEL.
* What are those codes & backstory?
* Did the mechanic do that or know you did it?
* What brand & part# springs did he install?
* New strut bushings too?

The shock and labor are both under warranty so that’s great. Take it back, but REMOVE the resistor(s) if he doesn’t know or your warranty is ****!

If OEM $150 z55/z95 or equivalent strut bushings were replaced with standard hydraulic strut caps that don’t have rubber bushings encapsulated, that could be another problem. P # 25940843.

 

[dkad260]

No one knows if new, active z55 struts are actually made to operate without power and not destroy themselves. You mentioned “I did make a set of resistors to bypass without a CEL but haven't tried that yet”.

I need to clarify.

My current setup is OE, factory harness connected to the strut.

I do not have a resistor connected to the harness, I also do not have a CEL.

I fabricated the resistor IN CASE I need to use it.

What are those codes & backstory?
* Did the mechanic do that or know you did it?
* What brand & part# springs did he install?
* New strut bushings too?

No codes, replaced OE struts at approx 120K miles.

Mechanic is definitely trusted, he only swapped the springs, I did the R&R of the assembly.

Reused OE spring, new OE spring seat, but the top mount I reused, does not have a bearing.

Shock (strut cartridge) was purchased from out of state dealer.

 

[petethepug]

BAM! Thanks, clear as day now. I’d say do the two prong approach. Contact the seller of the strut and ask for a RMA and prepaid shipping label on the sticking strut. After you get the return authorization order a replacement on the same call. They may ship it for free.

Once you have the replacement strut you can have the mechanic swap them out after you pull it. You can also inspect the strut bushing. It should look identical to the one above. The standard hydraulic version look different.

You can see the rubber bushings inside with the blue mark on it


Looking straight down all you can see is the steel washer covering the bushing. The GM OEM version do not have the part # on them but are stamped 060821 on the top & 051113 on the bottom. Not sure if that’s a date code or not.

 

[Doubeleive]

I need to clarify.

My current setup is OE, factory harness connected to the strut.

I do not have a resistor connected to the harness, I also do not have a CEL.

I fabricated the resistor IN CASE I need to use it.




No codes, replaced OE struts at approx 120K miles.

Mechanic is definitely trusted, he only swapped the springs, I did the R&R of the assembly.

Reused OE spring, new OE spring seat, but the top mount I reused, does not have a bearing.

Shock (strut cartridge) was purchased from out of state dealer.

not quite sure what you anticipate a resistor doing?
if you simply unplug the shock sensor harness and it does the same thing then it has nothing to do with electrical functional at all.
all the resistor will do is lie to the computer telling it the shock is connected, (when it is not) the resistor performs no other function