A true story from someone who should KNOW better - Ford Forums - Mustang Forum, Ford Trucks, Ford Focus and Ford Cars

RickMN · 01-22-2010, 17:59

There's this 1999 Mercury Sable. When the car shifts from 2nd to 3rd gear at around 30MPH, the headlights dim and the blower motor slows down to half speed. If you take your foot off the gas at highway speed (60MPH), it feels like the car is shifting out of overdrive--car immediately starts slowing down.

The owner (Rick) cleans the battery terminals and all the ground connections to eliminate electrical as an issue. Convinced that the 2-3 shift solenoid in the transmission is drawing too much current, he calls the transmission shop to set up an appointment. To get the side pan off the transmission, the shop will have to lower the engine cradle. The labor and new solenoids are gonna cost Rick about $500.

At the last minute, Rick decides to spend the $35 and call Ford tech support. The Ford expert says it doesn't sound like a shift solenoid because the computer would have caught that and set a trouble code (Ford computers excel at detecting transmission faults he says). He thinks it could be a slipping serpentine belt.

Huh? Why would it do that only at 30MPH?

Well, Rick, that's when the engine is revving up to about 2,300 RPM. Then, after the 2-3 shift, it drops about 600 RPM. So the belt is under the most stress (and likely to slip) right before that shift. The expert suggests I look at the belt and pulleys to check for glazing and or worn pulleys.

$97 dollars later, Rick has a new belt tensioner, idler pulley, and a new belt. The bearing in the idler pulley was so tight that the belt was slipping across it--it was even wearing grooves in the pulley as the belt slipped across it. So Rick pulled out his serpentine belt tool and rotated the tensioner. Then he slipped off the belt and let go of the tensioner. It took a few seconds for it to spring back.

Turns out, the belt tensioner was rusted and would stick when compressed. So the slow pulley caused the belt tensioner to rotate. Instead of springing back, it would stay there until the RPMs went down. So I wasn't really feeling it drop out of overdrive. It was just the tensioner springing back into place and putting the load back on the tight idler and alternator.

New parts installed and test drive shows the problem gone.

Morale of the story? If you're going to throw parts at the problem instead of diagnosing things properly, you should at least start with the least expensive parts first.

Transmission appointment canceled.

Rick embarrassed that he didn't check the belt first.

P.S. The back of the belt was glazed like a mirror, the ribs were fine. I changed that belt about 1 year ago.

**chipset** · 01-22-2010, 18:13

Gee. Funny thing is some people on this and other sites say " don't take too much notice of the guy that calls everyone a parts thrower and says send it out or have it tested by a qualified shop or someone that knows what they are doing ? " Glad you got it fixed. I bet you will never forget to look there first on another car that seems to have the same problem. Glad you got it fixed. Funny how a simple spring can cause so much
trouble. Good for you.

Sterling_Six · 01-23-2010, 07:43

Quote:

Originally Posted by RickMN

There's this 1999 Mercury Sable. When the car shifts from 2nd to 3rd gear at around 30MPH, the headlights dim and the blower motor slows down to half speed. If you take your foot off the gas at highway speed (60MPH), it feels like the car is shifting out of overdrive--car immediately starts slowing down.

The owner (Rick) cleans the battery terminals and all the ground connections to eliminate electrical as an issue. Convinced that the 2-3 shift solenoid in the transmission is drawing too much current, he calls the transmission shop to set up an appointment. To get the side pan off the transmission, the shop will have to lower the engine cradle. The labor and new solenoids are gonna cost Rick about $500.

At the last minute, Rick decides to spend the $35 and call Ford tech support. The Ford expert says it doesn't sound like a shift solenoid because the computer would have caught that and set a trouble code (Ford computers excel at detecting transmission faults he says). He thinks it could be a slipping serpentine belt.

Huh? Why would it do that only at 30MPH?

Well, Rick, that's when the engine is revving up to about 2,300 RPM. Then, after the 2-3 shift, it drops about 600 RPM. So the belt is under the most stress (and likely to slip) right before that shift. The expert suggests I look at the belt and pulleys to check for glazing and or worn pulleys.

$97 dollars later, Rick has a new belt tensioner, idler pulley, and a new belt. The bearing in the idler pulley was so tight that the belt was slipping across it--it was even wearing grooves in the pulley as the belt slipped across it. So Rick pulled out his serpentine belt tool and rotated the tensioner. Then he slipped off the belt and let go of the tensioner. It took a few seconds for it to spring back.

Turns out, the belt tensioner was rusted and would stick when compressed. So the slow pulley caused the belt tensioner to rotate. Instead of springing back, it would stay there until the RPMs went down. So I wasn't really feeling it drop out of overdrive. It was just the tensioner springing back into place and putting the load back on the tight idler and alternator.

New parts installed and test drive shows the problem gone.

Morale of the story? If you're going to throw parts at the problem instead of diagnosing things properly, you should at least start with the least expensive parts first.

Transmission appointment canceled.

Rick embarrassed that he didn't check the belt first.

P.S. The back of the belt was glazed like a mirror, the ribs were fine. I changed that belt about 1 year ago.

Hello and good day Rick:

LOL...like we haven't do this before...I have done things like this before also...I put my tail between my legs with embarrassment, and crawl back to my little hole on the couch, and curse my stupidity all the while.

I promise not to tell any one of this matter...LOL...take care.

jonvei · 01-23-2010, 07:56

What Ford tech support number did you call - im interested in calling them myself.

I have a 2000 taurus with the 24v Duratec which will not idle probably when the engine is cold - below freezing - it is not firing on all cylinders. when you drive along it works fine until you come to a stop and then it will usually shut off. so i changed all spark plugs and boots which didnt help. checked for vacuum leaks and havent found any. took it to Ford and they replaced 2 ignition coils because they said they were reading a misfire on cylinders 2 and 6. next morning when the engine was completely cold it was doing the exact same thing as before. will be getting my money back for the 2 new coils :{ there is no engine light on.

RickMN · 01-24-2010, 20:20

Misfire is most often caused by lower intake vac leak or bad coils. Also, a leak in the PCV valve rubber elbow. If you haven't already replaced the elbow, do it now.

**360ci** · 01-25-2010, 13:09

Quote:

Originally Posted by RickMN

Rick embarrassed that he didn't check the belt first.

No problem, we all have our moments.
I check my belt every time, before entering a restaurant that is.

foggysail · 01-25-2010, 18:24

WOW!!!! That certainly is interesting!!!

My 99 Taurus sometimes exhibits a dramatic slowing down while on the highway. It almost feels like I put the brakes on or the transmission dropped to a lower setting. A good example is when using cruise control, the car maintains its constant speed but when I go down a hill, sure the car should speed up but not always. Whe the condition I described occurs, the car actually seems to slow back to the speed set on the cruise control.

I have a trip to make so I will not be able to get to this for a week or more. I will check the belt along with the spring tensioner. When this condition happens it is very annoying.

Foggy