How often do the experienced mechanics on this board find that springs need to be replaced at the same time as the strut bodies?
I recently bought new struts off eBay for my '91 Buick LeSabre, and installed them using the original springs, seats, bearings, etc. One of the new struts has failed within two months. I’m considering buying new Monroe’s from a parts supplier, but they have suggested that the first one may have failed because the springs are worn - the theory being that the soft springs put more load on the strut itself. They proposed Monroe Quickstruts, which would make my life easy, but would of course cost more than struts sans springs.
The springs are visually in good condition - no rust, chips in the paint, etc. The store said that a shop should have checked my ride height while diagnosing the bad struts (and ball joints, and strut bearings, and sway bar bushings, and… sigh), but most don’t bother. My shop manual gives a large range for what the various trim measurements should be, so I’m stumped.
Do these springs really wear out?
I don’t buy that about the strut failing because of weak springs. Springs will sag after a while. There are various ways you can “boost” them. Look at www.jcwhitney.com. Go to a performance shop to see what they have. There are inserts that go between the spring coils, helper coils that go over shocks or struts, additional springs attached in various ways. A suspension (alignment) shop can advise you.
My opinion would be that you more than likely just got a bad strut. Anything that rolls off an assembly line is going to have a certain % of failures and maybe you must lucked into one of that certain number of crummy ones.
I’ve gotten tagged a number of times with defective new items and not always car parts.
A Maytag washer that was nothing but trouble from day one and don’t even get me going on the Chinese junk that Black and Decker is foisting off on the public now. 
the theory being that the soft springs put more load on the strut itself.
I don’t like that theory. The springs support the weight of the car. If they are old the car will rest lower. The struts/shocks don’t support the weight of the car, they simply resist movement. The struts should not even notice if the springs are a weak.
I would suggest replacing the struts (keep both strut pairs equal) and then get an alignment by a good front end shop. They can tell you the condition of the springs.
The struts/shocks don’t support the weight of the car, they simply resist movement.
This has always been my understanding. The strut is gas charged for whatever reason, but the resulting spring force is so small that I could push the shaft right down when the strut was off the car.
So I take it then that it’s not worth measuring the trim height?
Have you measured the free height of the springs? Just checking.
The car is going on 17 years old. The upper strut mounts are likely shot, and the spring isolators could be too. And the shop was right about one thing: check the ride height to see if the springs are sagging.
Frankly, it might be more economical to “spring” for the QuickStruts if you need to replace many of the other parts ala carte. Not to mention quicker and easier to DIY.
I didn’t think to do that when I changed the struts 2 months ago. At this point, I’m not sure I want to go through the work of taking the springs off just to measure them ahead of making a decision. The Quick Struts are looking mighty tempting right now.
I’m also wondering of the car was “bottoming out” over hard bumps. Buicks had soft springs even when new.
OP??? Was it bottoming?
grin Been away from the computer since early this morning.
On a normal big bump, the car doesn’t bottom in the sense that it’s smacking the rubber bumper at the top of the strut. Maybe I’m just not attacking the bumps hard enough… At very slow speed, over a tall speed bump, I can go through most of the front spring travel. These “new”, 2-month old, now junk, struts would creak on something like that.
At higher speed “yumps”, I can bounce go through most of the travel now. When these junk struts were new, it was a lot less bouncy.
Springs do wear out, and sometimes new struts are defective. I’d be leery of struts purchased off ebay, but they might be ok. Try a name brand this time and see if they do ok. The quick struts do save a lot of time so they might be worth getting, time is money.