Rod knock symptoms?

[Keasbey]

Hey guys,

 

To make a long story short, I just bought another subaru after a couple of years without one. Bought it a few weeks ago, and everything was fine during the test drive and the first week, no weird sounds or anything, except a loose exhaust heat sheild.

 

Since then it as developped a knocking sound, only audible when the engine is warm, in 1st & 2nd gear between 2k and 3k.. 1 time out of 10 it won't make it.

 

I can't replicate the sound in neutral, unless I go crazy with the throttle "bleeping"..

 

cold or warm idle sound fine except a few random miss. (40k miles on the sparkplugs.. )

 

A while back my 2003 impreza OBS developped a rod knock that sounded exaclty like this, but was audible at idle and when reving the engine at 3k and bleeping the throttle.

 

Any ideas how to know for sure its not a rod knock?

Edited May 28, 2020 by Keasbey

[Max Capacity]

Check the timing belt rollers. THey have been known to make that type sound.

 

When was the timing belt kit last replaced ?

 

Plugs should be good for 60,000 miles +

[Keasbey]

The timing belt was replaced 2 weeks ago by my usual subaru mechanic, but he charged me $80.. pretty sure it was only the belt and not the whole kit. I wonder if the heat sheild could cause such a noise?

[Infosecdad]

The timing belt was replaced 2 weeks ago by my usual subaru mechanic, but he charged me $80.. pretty sure it was only the belt and not the whole kit. I wonder if the heat sheild could cause such a noise?

 

Oh, you need to replace all the rollers and tensioner for the timing belt. If one of the toothed rollers seizes the engine is likely toast...

[Keasbey]

Wow that sucks, guess i'll have to get the parts and do it myself then.. but i wonder why it would only make it when the engine is warm..

[DaveWaters]

$80? Sounds more like an accessory belt replaced at that price. Replacing a timing belt is somewhat labor intensive and unless your mechanic is working for free or even for just a timing belt (part) $80 doesn’t quite sound right.

 

The timing belt tensioner is the part that fails and makes the sound similar to a rod knock. Plenty of YouTube videos available. Check that out.

 

Did this start after your mechanic was in there or before?

 

If your car is NA and not turbo I believe the interval for plugs is 30k miles. Double check your owners manual or google to be sure though.

 

Have you changed the oil since the purchase? How’s it look on the stick? Clean? How’s the level?

 

If you can post a video it might be helpful too.

[Keasbey]

The noise started before the timing belt replacement.. in fact, the headgasket were due when i purchased the car, so i asked my mechanic to replace them , and the timing belt at the same time, so he charged me an extra 80 bucks to do it.

 

I added 1qt of oil a few days after the purchase.. 5w30 castrol synthetic blend. I also filled the tank at a shady gas station coming back from the last owner's place. Which might cause detonation if the gas is bad and the sparkplugs are old.

 

I'll try to tighten up the heatsheilds, change sparkplugs and put some known good gas in it..

Edited May 28, 2020 by Keasbey

[DaveWaters]

Ok that makes some sense now about the TB cost. Since he most likely reused the tensioner I’d definitely check that. The tensioners have a process to reuse them where you have to very slowly press the piston back in over a certain period of time otherwise you can potentially damage the tensioner. So could very well be a floating tensioner.

 

Preignition kinda sounds like coins in a coffee can rather than rod knock which is more rhythmic.

 

 

A nice trick to quiet heat shield rattle is to wrap with large worm type hose clamps. Home depot and Lowes has pretty large clamps.

[Keasbey]

I'll definately check the tensionner and all the pulleys this weekend and pray it's that.. as for the worm clamp, there is already 6 of them on there hahah. The only other thing i can think about would be an exhaust leak, when cold it's closed and when the exhaust is warmed up it leaks... i'll try to het a video of it this weekend.