# 2001 Toyota Tacoma knocks when AC belt is tightened **URL:** \ **Category:** Maintenance/Repairs\ **Tags:** tacoma, toyota\ **Created:** [December 14, 2019, 1:41am UTC](https://community.cartalk.com/t/2001-toyota-tacoma-knocks-when-ac-belt-is-tightened/154658 "2019-12-14T01:41:42Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![PaulHall](https://avatars.discourse-cdn.com/v4/letter/p/73ab20/32.png) [@PaulHall](https://community.cartalk.com/u/PaulHall)\ **Post date:** [December 14, 2019, 1:41am UTC](https://community.cartalk.com/t/2001-toyota-tacoma-knocks-when-ac-belt-is-tightened/154658/1 "2019-12-14T01:41:43Z")
Previous owner had disconnected the AC My mechanic hooked it up but when the belt is tightened it make a knocking sound louder when under load. He could not find the cause. When the belt is loosened it goes away. The truck has 123,00- miles on it and had been sitting for 6 months before I got it. Finally just had him put the belt back on and the knock hasn’t got any louder. ---
**Author:** ![kurtwm1](https://avatars.discourse-cdn.com/v4/letter/k/13edae/32.png) [@kurtwm1](https://community.cartalk.com/u/kurtwm1)\ **Post date:** [December 14, 2019, 2:39am UTC](https://community.cartalk.com/t/2001-toyota-tacoma-knocks-when-ac-belt-is-tightened/154658/2 "2019-12-14T02:39:28Z")
> [@PaulHall](#): > > knocking sound louder when under load I assume you mean when the A/C is on? I am surprised your “mechanic” could not find the cause. A simple stethoscope could probably tell whether or not the knocking comes from the compressor. Cold be one of the compressor’s piston is going bad or the A/Cs pulley is on its way out. ---
**Author:** ![ok4450](https://avatars.discourse-cdn.com/v4/letter/o/e9bcb4/32.png) [@ok4450](https://community.cartalk.com/u/ok4450)\ **Post date:** [December 14, 2019, 3:13am UTC](https://community.cartalk.com/t/2001-toyota-tacoma-knocks-when-ac-belt-is-tightened/154658/3 "2019-12-14T03:13:02Z")
Check the harmonic balancer also. One thing you do not want is a loose or worn balancer knocking on the crankshaft nose. That can lead to crank damage which means major motor work., ---
**Author:** ![Barkydog](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/barkydog/32/2470_2.png) [@Barkydog](https://community.cartalk.com/u/Barkydog)\ **Post date:** [December 14, 2019, 5:45am UTC](https://community.cartalk.com/t/2001-toyota-tacoma-knocks-when-ac-belt-is-tightened/154658/4 "2019-12-14T05:45:47Z")
Find the source of the sound step 1. One could hope it is a bad tensioner. ---
**Author:** ![PaulHall](https://avatars.discourse-cdn.com/v4/letter/p/73ab20/32.png) [@PaulHall](https://community.cartalk.com/u/PaulHall)\ **Post date:** [December 14, 2019, 1:56pm UTC](https://community.cartalk.com/t/2001-toyota-tacoma-knocks-when-ac-belt-is-tightened/154658/5 "2019-12-14T13:56:32Z")
Sorry I forgot to mention he replacedvtge compressor but the knock was still there ---
**Author:** ![Cavell](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/cavell/32/43396_2.png) [@Cavell](https://community.cartalk.com/u/Cavell)\ **Post date:** [December 14, 2019, 2:37pm UTC](https://community.cartalk.com/t/2001-toyota-tacoma-knocks-when-ac-belt-is-tightened/154658/6 "2019-12-14T14:37:08Z")
That’s a good bit of info. New compressor. No belt. No noise. Related? ---
**Author:** ![kurtwm1](https://avatars.discourse-cdn.com/v4/letter/k/13edae/32.png) [@kurtwm1](https://community.cartalk.com/u/kurtwm1)\ **Post date:** [December 14, 2019, 2:40pm UTC](https://community.cartalk.com/t/2001-toyota-tacoma-knocks-when-ac-belt-is-tightened/154658/7 "2019-12-14T14:40:00Z")
In that case Barkydog may have the right idea… belt tensioner … or any other accessory with a pulley. However, it is possible to over tighten a belt and causing a pulley out of alignment and causing the knocking. If all accessories run OK, battery charges, power steering works, A/C work with the belt loosened a bit I would keep it that way. A stethoscope is still the best way to identify the source of an unwanted noise. Heck, a simple 2ft piece of garden hose will do it. ---
**Author:** ![VOLVO-V70](https://avatars.discourse-cdn.com/v4/letter/v/8e8cbc/32.png) [@VOLVO-V70](https://community.cartalk.com/u/VOLVO-V70)\ **Post date:** [December 14, 2019, 2:42pm UTC](https://community.cartalk.com/t/2001-toyota-tacoma-knocks-when-ac-belt-is-tightened/154658/8 "2019-12-14T14:42:58Z")
I don’t like to say this mechanic is in over his head but it just does not seem like it would be that difficult to locate the source of the knocking. ---
**Author:** ![ok4450](https://avatars.discourse-cdn.com/v4/letter/o/e9bcb4/32.png) [@ok4450](https://community.cartalk.com/u/ok4450)\ **Post date:** [December 15, 2019, 3:01am UTC](https://community.cartalk.com/t/2001-toyota-tacoma-knocks-when-ac-belt-is-tightened/154658/9 "2019-12-15T03:01:25Z")
I will just reiterate what I said earlier about checking the harmonic balancer. If it’s not too late already.