Help diagnosing engine sound

Hey all! First off, sorry if this is the wrong forum to post this in. I’ll move it if necessary.

So this is a video of my 97 Tacoma after running for about 10 minutes. Allegedly, the motor was swapped with a 114k mile engine about 9000 miles ago, and I have no reason to doubt the previous owner’s claim aside from no record of that on the carfax.

The engine sounds healthy to me based on what I’ve seen, but take note of the plastic-sounding “rattle” behind the valve train noise. It’s sounds… cyclical? If that makes sense. It actually sounds more like a vibration than a rattle, now that I think of it.

I haven’t taken my stethoscope to it yet, but it sounds to me like it’s coming from the top rear of the engine, near or under the intake manifold.

I’ve been working on cars for close to 15 years and I’ve never heard anything like this. Then again, I’ve never worked on a car this old, so maybe I’m being overly sensitive.

How’s this engine sound to you guys?
Previous owner also claims the following components were serviced along with the engine swap:

• Water pump
• Timing belt & associated components
• Rear main seal
• Clutch & components
• Oil pan

https://youtube.com/shorts/5FqVUZCwtMU?si=XfC8Zy40sHcQK78e

 

Sound is kinda muffled but it almost sounds like something rubbing on the timing cover.

 

That’s what I was thinking at first, but it sounds to me like it’s further back than that, near the intake manifold. Is the timing cover hard to take off for a quick inspection?

 

Just need to drain the coolant so you can unhook the upper rad hose to remove the upper timing cover.

 

Hmm. Shame I didn’t think of looking into that when I was flushing the coolant last week, lol. Maybe I can figure out some way to slide it along the upper rad hose so I can run the engine with the cover separated. Might help with ruling out the issue.

Or I suppose I could wait until I’m replacing the radiator, which I planned on doing next month (along with getting rid of those aftermarket clamps someone put on the rad hoses), but if it sounds like something’s loose it might not be a good idea to wait.

 

i would start with taking all of the accessory belts off and run the engine FOR A SHORT TIME and see if it goes away. Spin each accessory and see if it sounds rough like a failed bearing.

 

Radiator has a drain, just drain it into a clean container and pour it back in when you are done.

 

Roger. I’ll do that tomorrow while I have some garage time.

I mostly didn’t want to have to deal with burping it again but I guess it’s a pretty small task for the peace of mind. I’ll give it a shot.

 

Do you think there’d be any harm in reconnecting the upper rad hose with the timing cover off and running the engine? I’d like to see what the belt is doing with the timing cover off but don’t want to run it without the upper rad hose disconnected.

 

You can run it without the cover if you want. It doesn't create an airtight seal or anything

 

Thank you. Just wanted to make sure. I’ve worked on timing assemblies before but never on a Toyota, or on anything this old. Looks a hell of a lot easier to get to than the belt on my GTI. I’ll never buy another car with a transverse mounted engine.

 

Update: The issue is indeed the timing belt tensioner.

I took off the timing cover today and the belt does have a fair amount of slack in it. The belt is healthy and the pulleys still look new, so I do believe the previous owner did the belt, pulleys and water pump- but for whatever reason stopped short of doing the tensioner.

So, question time.

1. Is there anything wrong with replacing JUST the tensioner, since all the other components have been recently replaced?
2. Could I feasibly replace the tensioner without actually removing the belt?

Based on the videos I’ve watched, it really seems like I can just mark the timing for insurance and swap the tensioner. Of course that entails basically the whole timing job since the lower cover has to come off, but if I can get by without having to move the belt I’d call that a win.

 

Yes you can just replace the tensioner pretty easily, no need to remove the belt.

 

Excellent, thank you for the confirmation.
I just ordered the (wow $50 whole dollars he saved on the job) tensioner from rockauto, should be here by next weekend. Already got a buddy lined up to help me out.
Much appreciation for the advice! I’ll update again once I get it stitched back together in case anyone finds this thread looking for the same issue.

 

Might want to confirm the timing is still correct since the tensioner wasn't keeping the belt tight.

 

Yep, that’s the plan. I did check the cams while I was in there and they are still aligned properly. If it did jump anywhere, it’s on the crank. Couldn’t see that without taking off the lower cover.

 

New update for anyone following:

The tensioner was actually fine. I replaced it anyway since I had the part, but the issue was that the tensioner pulley was stuck in the un-tensioned position. I guess maybe the PO tightened that down before releasing the pin on the tensioner. As soon as I loosened the Allen bolt on the pulley assembly, the slack on the belt tightened right up. Torqued it back down to 30ft/lb per Timmy’s video.

 

Something isn't right there, the tensioner pulley pivot should be free floating with the bolt tight.

 

Hm. Any ideas? The pulley was replaced, it still looks nearly brand new.

 

It floated freely once I loosened the bolt. I didn’t check after I tightened it again because the belt was tight and I had already pulled the pin on the tensioner. Not sure how I can test it now without taking the tensioner back out I’m still at the point where I could do so but I’d really rather not