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Discussion Starter #1
Hey guys,

I just had the timing belt & water pump and crank pulley replaced at a local shop. Got the car back and when I started it the next morning it was making a screeching sound. I recorded a video of the sound:

The sound speeds up with the RPMs and goes away once the engine has had time to warm up. No abnormal sounds prior to going in for service. Any ideas as to what it could be?

Thanks!
 

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Sounds like something related to the serpentine belt right on the top there, should be obvious. How old is the belt? Perhaps it's just slipping when cold.
You can usually track the sound to a pulley. Check these:
1. V-belt auto-tensioner is tight to the timing cover and not flopping around causing a loose belt
2. Check the belt itself for rubbing against things it shouldn't. If they put a new vee belt on and the labeling is already rubbed off the back, there's a problem (can't see in the video since it's moving). I doubt they did as you have a supercharger, they probably just put the old belt back on since it isn't the stock length.
3. Idler pulleys rubbing?
4. Supercharger snout bearing?
Maybe (with the engine off) loosen the serp belt tension or take it off and try to spin each of the pulleys and idlers by hand to check. Since it goes away, its probably just the belt getting used to the new crank pulley. Not sure why you would completely replace that on a timing belt job unless the rubber harmonic damper was shot.
Can also try spraying light water on the belt when moving and see if the sound changes.
 

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Discussion Starter #3 (Edited)
Sounds like something related to the serpentine belt right on the top there, should be obvious.
Try to get close and track the sound to a pulley. Check these:
1. V-belt auto-tensioner is tight to the timing cover and not flopping around causing a loose belt
2. Check the belt itself for rubbing against things it shouldn't. If they put a new vee belt on and the labeling is already rubbed off the back, there's a problem (can't see in the video since it's moving). I doubt they did as you have a supercharger, they probably just put the old belt back on since it isn't the stock length.
3. Idler pulleys rubbing?
4. Supercharger snout bearing?
Maybe loosen the serp belt tension or take it off and try to spin each of the pulleys and idlers by hand to check. Since it goes away, its probably just the belt getting used to the new crank pulley. Not sure why you would completely replace that on a timing belt job unless the rubber harmonic damper was shot.
Can also try spraying light water on the belt and see if the sound changes.
Hey thanks for the reply.

I did check the v-belt tensioner and it is tight, and the belt has a clear path with no rubbing. I brought it back to the shop and had them look at it, and like you their first thought was the v-belt as it was not replaced and was reused, they soaked it in belt dressing and told me to see if that helped, it did not. The v-belt itself is still in good shape, is under 1 year old.

Sound isn't coming from the supercharger snout but rather directly under the power steering pump.

I used a rubber tube like a stethoscope to try and pinpoint the location of the sound. I was not able to locate a source, until I took some of the bolts off of the front timing cover and peeled it away enough to get the rubber tube in there. Low and behold the sound is loudest there.

I found one other forum post from a while back with someone who had the same issue. Screeching sound when starting

The conclusion was that a belt was not tensioned properly and needed adjustment, but he did not say if it was the v-belt or the timing belt.

I left the car at the shop this afternoon so they can start and in the morning and try and better locate the sound. I mentioned to them I heard it loudest coming from behind the timing belt cover.

I am thinking that the shop did not set the correct tension on the timing belt, because when I mentioned that it could be a tension issue they told me all the tension is automatic, but when I look through the service manual it states that there is an adjustment that must be set when a new timing belt is installed.
 

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Discussion Starter #4
Quote taken from the timing belt DIY:

4. Align the timing marks of the camshaft sprocket and crankshaft sprocket with the No.1 piston placed at top dead center and its compression stroke.


5. Set timing belt tensioner. (a. Using a press, slowly press in the push rod.) (b. Align the holes of the push rod and housing pass a set pin through the holes to keep the setting position of the push rod.) (c. Release the press.)
6. Install the timing belt tensioner. (a. Temporarily install the tensioner with the 2bolts.) (b. Alternately tighten the 2bolts.)
TORQUE: Tightening torque - 20 ~ 27Nm (200 ~ 270kgf.cm, 14 ~ 20lbf.ft)


7. Install the timing belt. (a. Remove any oil or water on the sprockets, and keep them clean.) (b. Install the tming belt in this order. Crankshaft sprocket(A) → Idler pulley(B) → Camshaft sprocket LH side(C) → Water pump pulley(D) → Camshaft sprocket RH side(E) → Tensioner pulley(F).)


8. Remove the set pin(A) from the tensioner.


9. Timing belt tensioner checking. (a. Rotate the crankshaft 2turns clockwise and measure the projected length of the auto tensioner at TDC(#1 compression stroke) after 5 minutes.) (b. The projected length should be 7 ~ 9mm (0.27 ~ 0.31in.))
 

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I doubt it's the timing belt, as the sound wouldn't go away until the teeth were gone (and also your engine). Timing belts don't slip, they skip which abrades the teeth and makes a clicking noise if anything. V belts will screech when slipping since they aren't positive drive. Maybe a bad water pump since that is the only thing directly under the power steering inside the cover? I agree it seemed loudest near there according to your video. Also the timing tensioner is hydraulic on these engines and doesn't need "setting". If a new one is put in you just bolt it on and pull the pin out. If they reused your old one, which would be a stupid idea, they still have to compress it and re-pin before installing just like it says in the manual. I guess it's possible they left the pin in and the belt is loose. Just like with the v belt, you can check the label on the flat side. If it's scraped off already, either one of the idlers or the water pump is having a difficult time turning and the belt is sliding on it. Hopefully they'll figure it out either way.
 

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Discussion Starter #6
I doubt it's the timing belt, as the sound wouldn't go away until the teeth were gone (and also your engine). Timing belts don't slip, they skip which abrades the teeth and makes a clicking noise if anything. V belts will screech when slipping since they aren't positive drive. Maybe a bad water pump since that is the only thing directly under the power steering inside the cover? I agree it seemed loudest near there according to your video. Also the timing tensioner is hydraulic on these engines and doesn't need "setting". If a new one is put in you just bolt it on and pull the pin out. If they reused your old one, which would be a stupid idea, they still have to compress it and re-pin before installing just like it says in the manual. I guess it's possible they left the pin in and the belt is loose. Just like with the v belt, you can check the label on the flat side. If it's scraped off already, either one of the idlers or the water pump is having a difficult time turning and the belt is sliding on it. Hopefully they'll figure it out either way.
Thank you for that clarification regarding the tensioner, to my knowledge the kit that was used included a brand new tensioner.

I do recall when I had the cover removed looking at the timing belt I did notice that the label was already starting to scrape off looked worn for a belt that is less than a week old, did not look as new as a brand new belt should look. I did not think much of it at the time but you make a very good point.

I will mention that to them tomorrow. With that said, I am wondering with the belt sliding on the pulley if I should be concerned with the integrity of the timing belt being compromised.
 

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Have to be careful with the terminology "tensioner" as some manufacturers refer to the left side pulley on the swing arm and some the actual hydraulic pusher below it. Some kits come with both parts and some don't. Generally it's good practice to replace both the pulley and the adjuster while in there.
135558

Yea if the label is burned off already, that's sign of a tension/slipping issue. Both of the cars I had timing belts on still had a legible (but faded) label after 120k miles and 70k miles respectively when I replaced them. The timing belt should be fine even if it slid a bit on the flat side (that part is thicker), just make sure the teeth are all still there and the same heights.
I'd be more worried about the life of the serpentine belt they just doused in dressing. I've heard negative things about that stuff. Belts shouldn't need any lubrication to operate, its only a band-aid for an improper install or an old one that needs replacing.
 

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Discussion Starter #8
Have to be careful with the terminology "tensioner" as some manufacturers refer to the left side pulley on the swing arm and some the actual hydraulic pusher below it. Some kits come with both parts and some don't. Generally it's good practice to replace both the pulley and the adjuster while in there.
View attachment 135558
Yea if the label is burned off already, that's sign of a tension/slipping issue. Both of the cars I had timing belts on still had a legible (but faded) label after 120k miles and 70k miles respectively when I replaced them. The timing belt should be fine even if it slid a bit on the flat side (that part is thicker), just make sure the teeth are all still there and the same heights.
I'd be more worried about the life of the serpentine belt they just doused in dressing. I've heard negative things about that stuff. Belts shouldn't need any lubrication to operate, its only a band-aid for an improper install or an old one that needs replacing.
Thanks for that good information! Even the label on my v-belt is in better condition compared to the one on the timing belt.

I will look into getting a replacement v-belt, its unfortunate that I already have to replace it because its relatively new, but I will look into getting one of the continental elite belts that use the old goodyear gatorback design.
 

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No problem sir. I happened to work for timing belt manufacturers for almost 10 yrs, hence the knowledge. Any word from the shop?
I would say no need to rush on the v belt if it's newer and only been sprayed once, but I'd just keep an eye on it and get a spare in case it does wear prematurely. It's the people who re-apply that dressing every so often that might have a problem. On a regular N/A car, I'd say a Gatorback belt is fine, but with the supercharger you may want better grip on the pulley with continuous vees. You've probably seen the Goodyears have the little grooves diagonally across for noise reduction, but at the expense of pulley grip. I like to minimize any slip so I get the most boost when hitting it :cool:.
Another interesting piece of info most don't realize is that rubber belts behave differently than most materials when heated; the neoprene actually shrinks with increasing temps rather than expanding. This can also explain why even worn belts tend to quiet down after warming up because they tighten a very small amount naturally and the tooth dimensions change. It's usually immeasurable (fractions of millimetres) due to the cord reinforcement and nylon tooth facing, but coupled with improper tensioning can cause extra noise and wear.
 

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Discussion Starter #10
I called the shop today to see if they had made any progress on locating the problem. They were able to identify that the sound is coming from behind the timing belt cover as I had suspected. However they stopped at that because they are "were to busy" with other cars to delve any further and might get to it tomorrow.

Car is still with them, and I suspect that because I already paid for the job back when it was finished originally its not a priority for them. While mildly infuriating, because one would think they should finish a job that they did not complete properly prior to servicing other cars, short of bringing the car elsewhere there is not much I can do.

Thanks for the info about the v-belt, i did not know that the gatorback design had less grip but it does make sense. I'll prob just hop on Rock auto and grab the same Gates one I have on the car now for the future!
 

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Car is still with them, and I suspect that because I already paid for the job back when it was finished originally its not a priority for them. While mildly infuriating, because one would think they should finish a job that they did not complete properly prior to servicing other cars, short of bringing the car elsewhere there is not much I can do.
Figures... that's about par for the course. Had a tranny shop do that to me way back when. Did they give you a warranty period on the work at all? If they warrantied it, then they are obligated to fix it, but you might get pushed to the back burner since they won't make any more money on it. Or they could tell you to deal with it and pound sand since they were your parts, not ordered by the shop.
 

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Discussion Starter #12
Figures... that's about par for the course. Had a tranny shop do that to me way back when. Did they give you a warranty period on the work at all? If they warrantied it, then they are obligated to fix it, but you might get pushed to the back burner since they won't make any more money on it. Or they could tell you to deal with it and pound sand since they were your parts, not ordered by the shop.
Yes the job is warrantied 90 days on labour, thankfully. Back when I was getting a quote for the job they asked if I wanted to buy the parts myself and pay cash for the labour. I declined, and paid them for their marked up parts solely for the paper record in case something like this did occur. Good thing I did!
 

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No problem sir. I happened to work for timing belt manufacturers for almost 10 yrs, hence the knowledge. Any word from the shop?
I would say no need to rush on the v belt if it's newer and only been sprayed once, but I'd just keep an eye on it and get a spare in case it does wear prematurely. It's the people who re-apply that dressing every so often that might have a problem. On a regular N/A car, I'd say a Gatorback belt is fine, but with the supercharger you may want better grip on the pulley with continuous vees. You've probably seen the Goodyears have the little grooves diagonally across for noise reduction, but at the expense of pulley grip. I like to minimize any slip so I get the most boost when hitting it :cool:.
Another interesting piece of info most don't realize is that rubber belts behave differently than most materials when heated; the neoprene actually shrinks with increasing temps rather than expanding. This can also explain why even worn belts tend to quiet down after warming up because they tighten a very small amount naturally and the tooth dimensions change. It's usually immeasurable (fractions of millimetres) due to the cord reinforcement and nylon tooth facing, but coupled with improper tensioning can cause extra noise and wear.
Yes, many "rubber like materials" show similar things with temp.....they expand when cooled, shrink when heated.
Another material that is "contrarian", can you name it....hint...very common.....
 

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Yes the job is warrantied 90 days on labour, thankfully. Back when I was getting a quote for the job they asked if I wanted to buy the parts myself and pay cash for the labour. I declined, and paid them for their marked up parts solely for the paper record in case something like this did occur. Good thing I did!
Sucks you are going through this...part of why I either know the shop, or pay 1/2 upfront for parts, sign an agreement (to cover them) for final payment and run/check things for a week or 2. Then final payment.
 

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Discussion Starter #15
The shop identified the cause of the problem to be a defective timing belt. Will update if the problem reappears!

Sucks you are going through this...part of why I either know the shop, or pay 1/2 upfront for parts, sign an agreement (to cover them) for final payment and run/check things for a week or 2. Then final payment.
That is a good approach and I will try and go that route the next time around!
 

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Update: Unfortunately when I went to pickup the car I noticed a loud ticking noise that I had never heard prior. Popped the hood and the engine sounded like it was a diesel and sounded like it was coming from the top of the engine, consistent with RPM. Had to leave it at the shop, they said they would look into it on Monday.
 

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I guess you canucks don't have a holiday this week, eh.
So they told you it was a bad timing belt, but wanted you to come and drive it home like that? Makes no sense to me. Can't drive the car with a belt that isn't timed right. Hopefully that ticking is something other than valve contact, otherwise that shop is gonna owe you alot more than a new belt. Beginning to lose faith in them :rolleyes:
 

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Discussion Starter #18
No we had a holiday this past Monday.

The series of events went down like this:

I called around noon to see if they had figured out what was causing the screeching sound, they told me it was a defective belt, and that they ordered a new one and the car would be ready for end of day

I went at the end of the day to get the car, and when I start it up I hear the ticking noise of inside the cabin. I open the hood in the parking lot and I was taken aback by how loud it was because I have never heard a ticking noise that loud in the 5 years I have had the car. I call the tech over, he listens to it then turns the car off and checks the oil level. Oil level was fine. He then checks to see if the front bank fuel injectors are all plugged in. They are all fine. Gives it some throttle and sees the ticking increases with RPM. He said when he finished putting the new belt on it was not making that sound. Idle was smooth and exhaust pulses at the tailpipes sounded as normal.

I REALLY hope its not valve contact, when I was researching what it could be a lot answers seemed to be that:

"rotating the crankshaft by hand when lining up the timing on the car can cause cause oil to drain back into the pan and air to get trapped at the top of the engine. Idling will not push the air out of the top of engine and the car needs to have a good amount of load on it to bring the oil pressure up to force oil back up"

https://www.reddit.com/r/Miata/comments/9ahbte
Obviously with the sound it was making I did not want to drive the car at all, so I asked him to check to make sure the timing is correct. So I guess I will find out on Monday :(
 

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Discussion Starter #19
double post idk how to delete this
 

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New update: after reassembling everything the shop noticed the car was still making the original screeching sound. The loud ticking as since stopped. They have decided to replace all the parts they installed with a new kit (timing belt, water pump, tensioner, idler pulleys)
 
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