2007 Mazda 3 Timing Belt Tensioner

I recently had the timing chain replaced on my 2007 Mazda 3 with 310,000 mi. Shortly after I started noticing a rattling sound when applying the gas pedal. I had heard this sound prior to the TC replacement but it was much quieter. I took it to another mechanic and he told me the tensioner was set incorrectly. So I returned to the mechanic that installed the new TC and he told me he couldn’t set the tensioner correctly because it was an automatic tensioner and had become faulty. If I wanted the rattling to go away I would need to replace the tensioner which would cost roughly the same as the repair for the TB. My question: is this accurate information? Or am I being scammed by a repair shop that did a sloppy job? Thanks in advance for any help.

how long is shortly after?
he should of put a new tensioner on when they did the timing chain. seems like they did not. either way they should be responsible for fixing it correctly.

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don’t let that mechanic touch your car again.

A real mechanic would have installed a timing chain set, which includes the tensioner.



Thanks for the reply.
This was not my usual mechanic (always been reliable) but did come recommended by him. Guess I need to find a new mechanic

Job was done in the last week of April. I heard the rattle as I drove away but it was similar in severity to what I’d experienced from the time I bought the car in 2016 with 200,000mi on it (only audible in 1st and 2nd gear when I was first driving the car for the day). So I thought “maybe it’s something not related to the timing chain”. After about 2 months the rattle had become so pronounced I took it to my wife’s mechanic. He said it’s likely the tension was improperly set. I called the guy who did the TC and he told me he put a new kit on but the tensioner wasn’t included and the one on the car now is likely faulty, but he was too busy to do that job (he said it wasn’t worth it though, because it was more of an annoyance than anything that would damage the car).

You say chain(s) were replaced?
Chain guides?
Sounds like worn parts and new chains.

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That looks like an oil pressure operated chain tensioner. At 310k miles maybe the oil pressure is lacking because the engine low end is worn out.

Next step should be an oil pressure check and is something I feel should have been considered before replacing the timing chain set considering the high miles.


I don’t see any timing chain tensioner adjustment procedure is needed for the 2.0 L engine. The spring in the tensioner part itself must be designed for the proper force at the factory. It has to be manually retracted and temporarily held in place as part of the installation procedure, so it’s possible something went wrong w/that.

He handed me a box of used parts when I paid him that match the parts in the above pic. The parts in the bottom pic weren’t in the box. Are those the tensioners and guides?

Tthe 2007 mazda 3 has an oil pressure sensor I believe. I’ll replace it and see if it gives me a low pressure reading.

Timing Chain Engine Owner MUST WATCH! Why it is important to REPLACE your timing chain. RATTLE NOISE - YouTube

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Your car does not have an oil pressure gauge so replacing the oil pressure sending unit will not tell you anything. You would have to remove the sender and connect an external gauge to find out if there is a problem with the oil pressure.

Oil pressure senders generally operate by turning off idiot lights and and so on around the 5 PSI mark. That figure and a bit more is not enough pressure to protect an engine or operate the chain tensioner which is oil pressure operated.

If the engine had far fewer miles on it oil pressure might not be as big a potential threat but with 310k miles I would want to know what I have before spending one dime and possibly making a decision to retire the engine or car.

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Ok thanks for the info. I’ll check that oil pressure asap

This is the tensioner. The guides wear more than the chains so I hope they were replaced.