Why are broken springs on MN12's quite common. - TCCoA Forums
 
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post #1 of 8 (permalink) Old 06-17-2015, 08:16 PM Thread Starter
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Why are broken springs on MN12's quite common.

Right after I bought my current parts car a 1997 Cougar back in 2007 I was showing to a buddies brother in law and he asked if I had replaced the intake yet or the rear springs? This was the first I'd heard of the infamous intake issue. Shortly after that the intake did in fact blow out. About a year later when I took the car in to have a noisy rear clunk diagnosed it turned out to be sway bar links and one or both rear springs had broken. A set off MOOG springs and sway bar links later all was well. A couple of years after that the front started banging about and I ended up replacing a upper control arm and the front springs. The daily driver I just bought of course needs rear springs. No surprise.

I'm just curious if there's a reason these cars seem to eat springs? Like bad metallurgy or bad design where they made the spring too compact relative to the load it carries. Or hard cornering over extends the spring on one side at full suspension travel. I know the cars are not light mind you but these are the only springs I've ever had to replace. I've upgraded springs in the past for handling or load carrying reasons but the orginal springs have always been intact. While we don't have the smoothest roads here in a north east ohio I'm not jumping train tracks or bottoming the car out. I have upon occasion run the car around a on ramp right at the tires limits but that's actually pretty rare. I don't beat on the car. Power brake it at traffic light or drive like someone with a newly minted license. My day jobs driving a truck and I have millions of miles of driving experience. I tend to look way down the road and drive very smoothly.

Another possible cause might be the panic stop where someone pulls out in front of you and you have to bury the brakes.

I somewhat suspect that it's a combination of a relatively small diameter spring. Less than stellar spring wire and possibly bit to much rebound designed in where the car tries to stretch the spring a little farther that it should and it breaks the coil.

Just curious if there's a root cause of broken springs on these cars or if it's just somewhat crappy materials in the factory springs.

I've read that broken springs seem to be pretty common so I doubt it's strictly a rough road or rust belt thing.
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post #2 of 8 (permalink) Old 06-17-2015, 10:17 PM
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Ever the contrarian I am I'm going to say rust belt and rough roads is the primary issue. Rear springs corrode the worst on these cars, all the road salt splash goes right at the whole IRS and the springs tend to be attacked. Other factor is the stock springs are progressive, in that a section of coil compresses before the other section of it does, which I'll speculate could cause extra fatigue in a specific point in the coil.

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post #3 of 8 (permalink) Old 06-17-2015, 11:06 PM
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Ive worked on a whole lot of Thunderbirds, and not once seen a broken spring. Oh yeah no salt or rust here.
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post #4 of 8 (permalink) Old 06-18-2015, 06:24 AM Thread Starter
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It could be just a rust belt thing then. Most of the people I know that have had these cars beyond the normal 3 year trade cycle have done rear springs. They normally break down at the very bottom in the spring cup of the LCA. Since you can't see the broken coil easily as easily there when it's on a hoist maybe some go un diagnosed.

Interesting point on the road salt angle. I'm not aware of the IRS channeling the road spray back and have always been pretty vigilant about keeping the fender wells hosed out during the winter months. Most of my friends that care about their cars will make a point of stopping by the coin op and blasting out the fender wells and rocker areas after a particularily heavy storm. It helps cut down on the fender lip rust quite a bit.

The broken springs I've seen have simply snapped off part of a coil. Normally at either end. More of a metal fatigue situation then rust. Some times the spring will still have paint on it and be looking good.

The guy that first tipped me about the springs and intakes was a certified master mechanic that had graduated from trade school and spent a about a decade at one of the local ford dealers. He's seen a LOT of these cars. All the certifications. He ended up being somewhat of a whiz kid with the electronics and was the coach and body guru at several Ford dealers. Then aggressively courted by the local Acura or Lexus dealers. Last I knew he was working as the chief coach and body tech at the premier Mercedes Benz dealer in town. Able to write his own ticket as far as pay and hours go. But he'd also spent his time in the trenches banging rotors on and off. R and R'ing transmissions and motors and all the other fun stuff. His creds pretty good.


But you did get me thinking. While the roads around here aren't much different than any of the northern states the railroad crossings can be amazingly rough on your suspension. One week it's fine and month later you'll drive across it and bury your molars. The crossing are the perfect storm for tearing things up.

Well thanks for your replies. I was wondering if it was a local phenomena or more wide spread. Be interesting to hear if it's common in some of the other areas.
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post #5 of 8 (permalink) Old 06-18-2015, 06:46 AM Thread Starter
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Originally Posted by XR7-4.6 View Post
Ever the contrarian I am I'm going to say rust belt and rough roads is the primary issue. Rear springs corrode the worst on these cars, all the road salt splash goes right at the whole IRS and the springs tend to be attacked. Other factor is the stock springs are progressive, in that a section of coil compresses before the other section of it does, which I'll speculate could cause extra fatigue in a specific point in the coil.
Not contrarian at all. I'm curious how widespread this is and speculation as to the cause I've always suspected the fact that their progressive. That the cars are relatively heavy. And have quite a bit of lean at the rear even with the sport suspension option that's loading one spring and unloading the other under steady state hard cornering. I'll add that it seems to effect the V6 and V8 cars equally as far as the rears go. Or maybe I'm a bit more gonzo than I think but I don't think I'm hammering on the cars much. No stop light Grand Prix's etc. Most of the time if I punch it it's from a roll. No drifting or smoky burn outs. No baiting the Ricers etc.

They seem to break about 70-80,000 mark. The guy that warned me was within 10K of predicting the springs and manifold going. The old daily driver was from FLA and owned by a elderly couple so presumably it had seen smoother roads part of its life. Your in Ill. Which isn't exactly the sunny south either. Have you seen this?
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post #6 of 8 (permalink) Old 06-18-2015, 06:57 AM
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Mine still has the Aug 1995 springs in it, i plan to replace them anyway due to wanting a stiffer ride.

My theory: Most of these cars end up getting beat to death by their third owners. Most view the thunderbird as a cheap car nowadays, a banger. Sorry to say it but these are the forgotten fords, nobody appreciates them for what they are, just they are cheap and have features that a toyota lacks.
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post #7 of 8 (permalink) Old 06-18-2015, 07:36 AM Thread Starter
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Mine still has the Aug 1995 springs in it, i plan to replace them anyway due to wanting a stiffer ride.

My theory: Most of these cars end up getting beat to death by their third owners. Most view the thunderbird as a cheap car nowadays, a banger. Sorry to say it but these are the forgotten fords, nobody appreciates them for what they are, just they are cheap and have features that a toyota lacks.
Or 4th, 5th or 6th owners I hear what your saying.

They did a set on my uncles. One retired owner that strictly drove the car back and forth to the marina he owned about 6 miles from the house. All smooth roads. All summer miles. Another couple I know had about 4 MN12s and did several. Most of these were V6 cars. Both Cougars and Tbirds. He's a car collector and the cars were always spotless even in winter. Extremely well maintained. So these weren't being flogged by kids.

My new DD was driven by a kid going to college and is suffering from what I'll call a distinct lack of maintenance. Overall though the cars shockingly clean underneath. I expected the springs to be broke and it needing sway bar links. And it does. I'd be more surprised if it wasn't driven hard and put away wet. Certainly no one was doing anything other then what was required to keep it going as far as maintenance is concerned. I'm the third owner. The original owner had it up till about 2013 or so. And was no surprise a old per gent. At least around here I see quite a few of these coming up that are one owner or have been in the same family and passed along. So while I'd not want to guess a ratio there 25-30% probably about ballpark. But yeah it's not to hard to imagine some kid that really would rather have a souped up accord just beating the piss out of one of these.

Jersey has surprisingly good roads for a northern Atlantic seaboard state. PA where this one came from however does not. If New Jersey took care of the roads like PA does I suspect they'd find the director of the state DOT in the trunk of a car in the pine barrens. The difference is pretty dramatic. Ohio does a pretty good job for the most part on the interstates and state routes. Local roads are left up to their respective municipalities and vary wildly. The last two winters have here been brutal and and it shows.

I like this forum. I'm glad to see the cars are appreciated for what they are. 20 years after the introduction I still marvel at what a departure these where from Ford. A true clean sheet of design and a watershed of engineering. Well thought out and a great balance of ride, handing and power. In some ways they are secret super cars. But I realize we are a minority. But it nice to see the dedication people have.

Last edited by 97CatMan; 06-18-2015 at 07:46 AM.
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post #8 of 8 (permalink) Old 06-18-2015, 08:16 AM
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Originally Posted by 97CatMan View Post
Or 4th, 5th or 6th owners I hear what your saying.

They did a set on my uncles. One retired owner that strictly drove the car back and forth to the marina he owned about 6 miles from the house. All smooth roads. All summer miles. Another couple I know had about 4 MN12s and did several. Most of these were V6 cars. Both Cougars and Tbirds. He's a car collector and the cars were always spotless even in winter. Extremely well maintained. So these weren't being flogged by kids.

My new DD was driven by a kid going to college and is suffering from what I'll call a distinct lack of maintenance. Overall though the cars shockingly clean underneath. I expected the springs to be broke and it needing sway bar links. And it does. I'd be more surprised if it wasn't driven hard and put away wet. Certainly no one was doing anything other then what was required to keep it going as far as maintenance is concerned. I'm the third owner. The original owner had it up till about 2013 or so. And was no surprise a old per gent. At least around here I see quite a few of these coming up that are one owner or have been in the same family and passed along. So while I'd not want to guess a ratio there 25-30% probably about ballpark. But yeah it's not to hard to imagine some kid that really would rather have a souped up accord just beating the piss out of one of these.

Jersey has surprisingly good roads for a northern Atlantic seaboard state. PA where this one came from however does not. If New Jersey took care of the roads like PA does I suspect they'd find the director of the state DOT in the trunk of a car in the pine barrens. The difference is pretty dramatic. Ohio does a pretty good job for the most part on the interstates and state routes. Local roads are left up to their respective municipalities and vary wildly. The last two winters have here been brutal and and it shows.

I like this forum. I'm glad to see the cars are appreciated for what they are. 20 years after the introduction I still marvel at what a departure these where from Ford. A true clean sheet of design and a watershed of engineering. Well thought out and a great balance of ride, handing and power. In some ways they are secret super cars. But I realize we are a minority. But it nice to see the dedication people have.
Mine was a two owner car, first drove it hard, second barely drove it, 88,000 miles in Jan when i bought it. I went down to Laurel MD to buy it from a guy who bought it to flip it.
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