Mechanical Tensioner Issue

[RogueAngel]

Something to consider when deciding to change from the hydrualic tensioner to the mechanical tensioner for the 420A timing belt.

I installed a mechanical tensioner at the completion of my engine build with no problems for about 8k miles. I was driving home from work at less than 40 MPH when the belt jumped two teeth. I won't know if there is any damaged yet to the valves until I get to work on it this weekend.

I'm switching back to a hydraulic tensioner as I had 203k on the original with never a problem.

 

[Josh97eclipse]

Did you set it right and torque it down properly?

 

[RogueAngel]

Yes, torqued per spec. Belt is still tight and looks like nothing happened, but it jumped.

 

[Leonthefaded]

I've been debating on if I will be switching to the mechinical tensioner or using hydraulic. I've read alot of reviews and feedback about both, I've never heard till now about timing jumping.

Where you timing marks correct before it jumped? I only asked because I mistakenly didnt check my Prelude when I did its timing.

Where did you buy the tensioner from?

 

[RogueAngel]

Yes, the timing was set correctly and the engine was running fine until the belt jumped. Not so much after!

Purchased from parts dinosaur I believe.

 

[Josh97eclipse]

Whats the car running like. You are leaving out key info, like CELs etc. Now I doubt the tensioner failed, is it the stock belt? or the gates racing belt???

 

[Leonthefaded]

Im wondering what belt was used too. Only two belts I know of for the 420a on the market are the gates ones. Blue or oem. And ones made by gator.

Possibly the belt itself may have been defective?

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[knochgoon24]

There's a reason why mechanical tensioners are only recommended for race applications. You need to keep an eye on them.

 

[Alex7747]

why would you go to a mechanical one if the hydraulic ones are proven?

 

[RogueAngel]

More info:

Belt? - Gates blue. Condition now? - unknown, it is still on the car.

How does the engine run? Timing off by two teeth. As you would suspect; like %^$#!

Any CELs: You don't get a CEL with a Megasquirt standalone.

Symptoms when it died? Wouldn't idle, AFR jumping from rich to lean.

Why switch to mechanical tensioner?: According to the info on the net; the tension on the belt is more consistent. Additionally, much easier to set timing when the engine is still in the car.

I'll give another update after I get the timing re-adjusted with a new hydraulic tensioner.

 

[Leonthefaded]

Hrmm.... hopefully that belt isn't looking like a micro v belt or something (shouldn't) but I would like to see pics of the old belt once its out
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[VelocitàPaola]

Yeah, me too. I've never heard that these mechanical tensioners were meant for race only applications, but I've noticed the people saying this recently all own 4G63's...

Other benefits aside, mechanical tensioners are definitely easier to deal with when you have to remove the timing components frequently. As I said in another thread, I've been running one for 10k+ miles without any issues.

OP, do you have the timing belt cover installed? Are you sure a small rock, pebble, or other foreign body didn't fall between the belt and a gear causing the timing to jump?

 

[Shake_Zulla]

What I don't get is how the tensioner became loose enough to jump two teeth and then became tight enough to run again two teeth down at what I'm guessing is low rpm and torque (40mph?). I'm at least guessing you ran it after it jumped from this.

More info:


How does the engine run? Timing off by two teeth. As you would suspect; like %^$#!



Symptoms when it died? Wouldn't idle, AFR jumping from rich to lean.

.

Besides what paul said I would check the wear on your timing pulleys. If the tensioner was loose it would still be loose... you know?

 

[Leonthefaded]

What I don't get is how the tensioner became loose enough to jump two teeth and then became tight enough to run again two teeth down at what I'm guessing is low rpm and torque (40mph?). I'm at least guessing you ran it after it jumped from this.



Besides what paul said I would check the wear on your timing pulleys. If the tensioner was loose it would still be loose... you know?

+1 which if not operator error, points to belt failure?

 

[Josh97eclipse]

And I doubt its belt failure if he has the gates racing belt.

 

[Leonthefaded]

And I doubt its belt failure if he has the gates racing belt.

No ones gonna know unless he opens that timing cover and posts pics!!

 

[RogueAngel]

Okay here's the update, got the timing belt cover off and the engine wasn't at TDC. Belt didn't jump - Sorry for any concern I caused.

Took the injectors to an injector shop and had them tested and picked up a noid light. Injectors test out near perfect. Noid light would barely light up, the filament just turned orange, when cranking. Continuity for the wiring is good from injector harness back to the MS harness connector and 12 V at the injectors.

Sent the MS back to SymTech to check out the drivers.

BTW, it's not nice to assume everyone on the site is male.

 

[glowryder]

yea deff user error.

side note for the race application theory.. IF that were true.. why would mopar use them on standard neons and stratus etc..last i checked, those wernt race cars . Mechanical has BEEN PROVEN to be better then hydro. hydro sucks. I blew one at 3K... its very hit and miss with hydro Mechanical FTW. so go mechanical, its an upgrade.. to 2005+
so whom ever started the "race" only is incorrect. Its just better overall, untill you get into bigg cams, then it needs some upgrading to the spring.

 

[starfish]

Okay here's the update, got the timing belt cover off and the engine wasn't at TDC. Belt didn't jump - Sorry for any concern I caused.

Took the injectors to an injector shop and had them tested and picked up a noid light. Injectors test out near perfect. Noid light would barely light up, the filament just turned orange, when cranking. Continuity for the wiring is good from injector harness back to the MS harness connector and 12 V at the injectors.

Sent the MS back to SymTech to check out the drivers.

BTW, it's not nice to assume everyone on the site is male.

By the way!Nice clean sexy car!!!

 

[Leonthefaded]

I apologize I didn't read your profile and realize you were a female.



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[DSMReviver]

The timing belt probably have too much slack...Improper tension on the belt.