Hi all,

New to this forum.

Got a question here for the gear heads.

I have a 2001 mazda b4000, around 144 000 kms on it. The fan really revs high when ever you put the gas on and takes about 1 second after you release the gas to rev down. The dealership said it was probably the fan clutch. The service engine light has been on for a while but the dealership said it was only for something very minor, an emissions reader or something.

On a referral from a friend, I took the truck to his mechanic to save some hourly rate money on the fix. He opened the hood and saw the engine was shaking a bit. At first he said that would attribute to the fan noise as everything relates to the engine being steady. He then phoned me and said the problem was related to a gas filter, I take it that not enough gas was going in and was effecting the engine performance which in turn would effect the fan. To boot, this mechanic has a very thick accident and is hard to understand.

He then changed the fuel filter and reset the truck's computer.

He said that I'd have to drive the truck for 8 hours for the computer to relearn my driving habits. (this sounds a bit fishy to me, shouldn't take more than an hour or two) The truck still has the loud loud fan reving, and now when the air conditioning is on, it idles at 1000 and then drops to almost a stall like (100 rpms) and then revs back to 1000 and back to down to 100 ever 3 or 4 seconds. When the a/c is off it revs around 1000 and slightly goes higher to 1200 and back and fourth but that stops after the truck warms up.

This doesn't sound like its learning anything. I"m wondering what to do from here. I feel like I spent a lot of money on a fix that hasn't fixed anything and I'm being taken for a ride with the computer needing 8 hours to relearn. Part of me wants to take it back and get it fixed properly for free but at the same time, if he couldn't figure it out the first time who's to say he'll get ir right this time, and all that is wasted is my time. We only have one vehicle and it its a real pain in the *** to have it out for days at a time. I just want it to run smooth. My wife is scared to drive it and its affecting our vacation to her parent's cabin this weekend, now we need to borrow a car for the 6 hour drive.

Any help would be great.

Cheers,

John

 

Fan clutch for the noise. It is not controlled by the PCM. The idle problem sounds like the IAC valve and can probably be cleaned along with the throttlebody.

 

He wasn't BSing you on the computer, it needs to go through a certain drive cycle to relearn. My 2002 manual for the B4000 is 3 states away but here is the 96 procedure which should be close enough.

1. Start the engine
2. Drive for at least 4 minutes
3. Once the engine coolant has reached 180 deg F idle for at least 80 seconds.
4. Acclerate to 45 mph at 1/4-1/2 throttle for about 8 seconds.
5. Drive between 30 and 45 mph for at least 4 minutes.
6. Drive for 1 minute between 30-40 mph while maintaining steady throttle.
7. Decelerate at idle for 80 seconds
8. Accelerate to 55 mph at 1/4-1/2 throttle for about 8 seconds
9. Decelerate with throttle closed for 10 seconds
10. Repeat step 8
11. Repeat step 9
12. Accelerate at 1/4 to 1/2 throttle to a steady throttle and hold for 8 second.
13.Cruise at a speed between 40-60 mph for 5 minutes at steady throttle.
14. Drive between 25-40 mph for 10 minutes making at least 6 stops between.
16. Decelerate to an idle.
17. Turn the vehicle off.

Most of this will happen over normal driving but it may take mulitple trips for an average driver to trigger all the events. The above list is usually a MINIMUM for the computer to make it's reset diagnostic. Many cars will require several of these cycles to be completed with a cool down time in between to fully adjust the adaptive learning of the computer.

I second hixx on the fan if it is mechanical and not disengauging at high rpm then it must be the clutch. If it is electric it is computer controlled and has a low and high mode, when the computer reads the truck is not moving from the vss or the prndl switch and is revving at a high rpm it will activate the electric fan in high mode which is perfectly normal.

 

Thanks for the help guys.

I took the truck to a reputable dealership instead of some shady mechanic. The old mechanic may have not lied about the computer relearn but he didn't even look at the fan. It took the dealership all of 1 hour to figure out the problem and give me a quote. This other mechanic took the low road and told me to fix things that wouldn't solve my problem so he could get more money and in the end waste my time. Then he feeds me some more "BS" about the computer relearning (true it might take time for the computer to relearn things but it was going to relearn to fix my problem..ever. So telling me in 8 hours of driving my fan noise will be gone, sounds like BS to me). Sorry cleaning a fuel filter would not be on the top of my list to fix a fan noise. Maybe after you exhausted looking at the FAN mechanism first then maybe start looking elsewhere.

Turns out the viscous fan seized. Parts needed for the repair included a fan drive and a belt 'v' (I'm guessing a fan belt). Works fine now. No noise, no idling issues. Cost of repair was $663.56 CDN including tax.