anciano

Below is the condition in which I found the front spring on my new (to me) '94 convertible:


So I replaced it, and cursed the PO for not heeding the plain warning in the owner's manual:
But the cynic in me got the upper hand. First of all, I've messed around with various types of fiberglass resin for some time on boat projects and except for one solvent -- acetone -- I wasn't aware of any serious damage these substances could cause. On the other had, the use of fiberglass in an application where the component would be subject to constant flexing and stress seemed to me a little strange. Which led me to consider the possibility (this is where the cynic comes in) that the cleaning agent disclaimer was a simple case of CYA by GM. After all, if you anticipate that your design might have flaws, it's just good strategy to put in a pre-emptive excuse to shift the blame for failure to the owner. Lawyers everywhere have earned handsome bonuses for this.

So I ran a little experiment with the old spring on the undamaged side. For 10 days (or so-- lost count, but more than a week) I subjected the spring to intensive exposure to those very same nasty agents GM warned against. I wrapped the spring in cotton flannel, and then soaked the flannel in three separate places with 1) acetone (which I know to be very hard on resins); 2) brake fluid (why not?; it eats up paint); and 3) petroleum distillate-based carb cleaner, which is the same stuff as most traditional engine degreasers. I also subjected another section of the spring to a daily dose of oven cleaner, which is highly corrosive. So the degreaser, solvent and corrosive agent categories were all covered. Every day I soaked the rags with their respective liquids, and then covered the rags with plastic to make sure they stayed wet as long as possible to maximize exposure -- certainly longer than would occur if someone washed their engine with any of these substances and then rinsed it down. Note, too, that the delamination on my spring was on the BOTTOM -- not on the top where these nasty agents would be expected to pool and do their damage if not rinsed off.

And the result:


Yup, nothing but a very shiny surface. I tried scratching and chipping at it to see if any softening had occurred, and pounding with a hammer to see if any loose fibers could be dislodged. Nuttin'.

So my cynical side has been greatly strengthened. I guess the next step is to cut up the spring and soak the pieces for a long time in these various solvents -- but I'm pretty convinced right now that the disclaimer in the owner's manual is nothing but corporate bullsh*t.

92ragtop

Not only are you cynical, you're thorough too!

So, if it's not chemical exposure, it makes you wonder what causes some springs to fail. Maybe Age + hours of abuse?

Aardwolf

Good info, thanks for posting the tests!

anciano

Plus heat cycles. It's also possible that some crack and some don't because of the composition of the resin GM used to lay these things up. Most fiberglass resins -- whether epoxy, ployester or vinylester -- use a two-part mixture. If the mixture proportions were not right on some production runs it may have shown up as failure later.

It's really impossible to know.

I wonder when GM started putting that discalimer in the owner's manual. From the very first year of the composite spring?

PLRX

I remember when I bought my 96 project both monosprings were cracked but, not as bad. Yours looks completely broken.

leesvet

You call it whatever you want. Heres a couple facts regarding composite springs.

Your "experiment" was not very scientific nor controlled. There are no conclusions that can be drawn from that. Guessing won;t produce the same results if the ingredients are unknown.

Please continue reading....

Potassium hydroxide, sodium hydroxide OR phosphoric acid, sulfic acids,and the other common degreasers and/or aluminum wash-brighteners (Acids & Bases at the extreme end of the Ph chart) will chemically break the bond in the resin and the spring cracks first time its stressed.

Done it.

Extreme PH hi/lo chemicals effect it. There was the owners manual warning, a service bulletin (GM or DOT) that came out several yrs into C4 production, and other magazine, tech articles and aftermarket warnings about this.

I learned of this when I was spraying my alum rear end with wheel wash (phosphoric or sulfic acid blends-on the shelf, Eagle-1 etching wheel wash) to keep it clean. This had a nice effect on the batwing and half-shafts but cracked the rear spring everytime. I eventually took my new HD 499lb/in 84-Z51 spring and plastic-dipped it so it had a barrier or a skin to shield it from the chemicals.
End of problem.

The front spring does a little better because its covered with guards and mounts so only the very ends are exposed but it will still break almost instantly when exposed to acid or HD (lye) degreasers.

Its the chemistry...

socalman

The chemical getting on the spring will take months or years to break down the coating, but it will. Otherwise, why does a spring ever crack & break?

JackDidley

150,000+ miles on my 87. Never gave the springs a second look. Maybe I should.

anciano

No, it was like yours, delaminated down to what appears to be a couple of layers of glass. I actually thought about repairing it with some epoxy to hold the frayed portions down and a couple of wraps of new glass mat around the fractured part. The problem is that I don't know what kind of resin they used originally, and for any kind of good bond they should be compatible.

Oh, gosh, no Nobel Prize for me? Dang, I wasted my time on this.

I don't pretend to be a chemist or materials engineer, but I tried to use the same substances they warn against. If there is a specific list of chemical agents known to damage the spring, why isn't GM more specific in their warning? I was just trying to replicate what someone might predictably use to clean the engine, and I have yet to hear of someone pouring phosphoric acid over it (if someone does I'd like to watch -- I used it to clean the rust out of an old motorcycle tank once and left it in a few minutes too long. After that the tank made a nice watering can for the flowers since it had so many pinholes.).

But fortunately I have some acidic wheel wash stuff (it burns my skin if I don't wear gloves) so I'll try that next. I'm not aware that any resins are particularly sensitive to acids, but we'll see. As far as the lye degreaser, that's precisely what oven cleaner is, and it didn't have any effect at all. If you don't think it is a sufficiently strong alkaline concentration, spray a little on your arm and leave it there for a while. Best to try it on a tattoo you want to get rid of.

SJW

I'd be curious as to what the results of your experiment might have been if the spring had been stressed after the chemicals were applied. I suspect you might have seen quite a different outcome.

Live well,

SJW

anciano

That might very well be the case. OTOH, the part of the spring that flexes during use is pretty much entirely the part outboard of the mounting pads on each side. The middle part of the spring is held mostly static when it is installed because of the locating ears on the brackets which hold it up to the frame; and my spring (along with PLRX's and I imagine many others) had deteriorated greatly in that static middle portion.

The only additional stress on that middle portion, as far as I can tell, is heat stress from its proximity to the engine block. But arguing against that is the fact that the damage occurred on the bottom of the spring away from the heat source. And, incidentally, awayfrom chemicals that might be used to clean the engine and which would be expected to pool on and affect the upper surface to a greater degree.

BTW, I'm currently testing Socalman's theory of acid damage, using a wheel wash solution comprised of phosphoric and oxalic acids and applied via a soaked rag as before. I put it over the portion that previously had the acetone bath, so there will be no protective grease or oil layer to inhibit the acid. He said the spring "will...break almost instantly when exposed to acid or HD (lye) degreasers" so it should not take long to prove or disprove his theory. The lye (sodium hydroxide) oven cleaner certainly had no effect after days of exposure.

Results to follow after a day or two of intensive exposure. I wish I had some battery acid to dump on another section as well, even though GM does not warn against that kind of spill.

Maybe we should refer this one to the "Mythbusters."

leesvet

Use your acid and stress the spring later on. Be sure its Phosphoric acid for cleaning aluminum wheels. Eagle 1 is what I use to break springs.
Stress it anyway you wish...

it's gonna crack if its flexed enough. Thats a given. acid is lo or no Ph and destroys the chemical bonding in the epoxie glass laminate.

we'll see...

Why< i am not sure. Pointless exeriement since this is well documanted....oh well...............[proceed at your leisure..

anciano

As noted above, the solution I'm using is phosphoric acid and oxalic acid. I'm not clear why you are in the habit of destroying springs, however. It seems like there are cheaper hobbies to pursue.

Two things to note here:
1) according to information from chemists who make the stuff, epoxy resin has generally good to excellent resistance to acids. There are relatively few solvents that are "not recommended" for contact with epoxy resin, and acetone -- part of my experiment -- is one of them. I'd like to see your source for the fact that acid is damaging, particularly in the low concentrations found in on off-the-shelf cleaning solutions. If you wanted to buy the stuff technically classified by chemists as a "corrosive" (more than 25% concentration by weight) instead of just an "irritant" you would probably need a license.
2) HOWEVER -- I'd also like to see your source of info that this spring is even made with epoxy resin. In the FSM where various components of the car are identified by their chemical composition (section 10-1-20) there is no listing for the transverse spring. So where did you get the idea that epoxy resin was used in it?

Well documented? I haven't seen any documentation. Please explain, or better yet, provide the documentation.

It's probably easier to document the opposite. If we hear from just one owner who experienced a damaged spring but who never used a cleaning agent near it that would pretty much call your theory into question, wouldn't it? I'd also be willing to bet that there are many owners who have used these cleaning agents without problem. But as someone once said, "the plural of anecdote is not data."

I'm not trying to change the world here, just noodle a little bit on this issue of damaged springs which has vexed some of us.

socalman

twasn't me

anciano

You are correct, Socalman. It was Leesvet who said that. Sorry.

If I splashed chemicals around with the same carelessness I'd be blind pretty soon.

mashinter

Re: Fiberglass spring fatigue life from Corvette from the Inside by Dave McLellan, pp. 87-88.:

Metal spring would go as few as 200,000 lab. cycles. The fiberglass spring went 2,000,000.

"The springs showed some fraying or delamination of the outer fibers, but we could not measure the effect of this on spring rate or load capacity."

Dave mentions heat above 220*F. as the biggest threat to strength of the epoxy resin.

"The (fiberglass) spring proved to be a total success."

littlesk8cracker

funny, i just broke the front spring on my 94 convertible also! mine was due to hitting a car battery at 50 mph though. didnt break on impact, snapped in 2 pieces 2 days after the hit

anciano

A TOTAL SUCCESS when it delaminates after 2,000,000 cycles?!!

I wish I could retrieve that article. How do they define lab cycles and how did they test them? For goodness sake, failure of a metal spring after only 200,000 cycles? There are original leaf springs on Model T's still functioning. Somethin' ain't right here.

Please post the entire article if you can, or at least the relevant parts. I think this may be the answer to the spring failure riddle.

BTW, no effect at all after days of soaking with phosphoric/oxalic acid solution (however, I found that it does a really nice job of removing oxidation from an old brass bowl). I'm out of nasty chemicals, now. Anybody got a flame thrower?

mashinter

Corvette from the Inside is a copyrighted book, still readily available, so I can't reproduce it here. If you want to know what makes your '84 and later car tick, buy this book. For me, a "must have".

If it were a valve spring, 200,000 would be a disaster. A valve spring has to flex to max. stress every cycle. A suspension spring has to be designed to not fail or sag (steel) at full metal-to-metal flex, but it probably never sees that flex.

The spring is tested in the lab. at the equivalent of full metal-to-metal suspension travel. 200,000 is a lot of that flex. 2,000,000 is way beyond adequate for a new spring. That's all you can do in the lab.

There may be something that reduces the life in the car (heat) or there may be a manufacturing issue that results in delamination in some springs. Dunno.

The steel rear leaf spring in the '63-'80 cars fails much more often than the plastic springs in '81 and later. That is an engineering success, particularly when it is much lighter. (If it's cheaper, it would be a total success. Dave writes cost is competitive with coil springs. Close enough...)

anciano

Well, that makes sense. Laid-up fiberglass using the proper resin is inherently more flexible than most high-strength metals, and probably better suited to high-flex applications (like a compound archery bow, for example). But it also raises the question of why the testing methodology called for "full metal-to-metal" stressing, which if I interpret it correctly means that the piece is effectively folded in half so that the ends touch (of course, I may be completely off the beam on this interpretation). Normally testing is designed to simulate actual use conditions, which in this case would mean maximum suspension-mounted flex combined with engine heat cycles.

Since common chemical reagents do not seem to have an effect on the spring's integrity, I'm inclined to stay with my original suspicion that the disclaimer was intended to deflect liability issues. As you say, why the springs fail is still an open question, but cycle fatigue combined with high temperatures would seem the most likely culprit. Another possibility is that some batches were laid up with an improper ratio of resin to hardener which would result in deficient curing. I guess the only way to know that is to compare VINs and see if there are some clusters of failures -- but that's certainly not worth the time and effort.

Anyway, I've got a replacement in mine now and what are the odds of getting TWO bad ones?