Engine runs noisy after cold start.

[ultrasonic]

The Victim: 91 Sport Sedan, 5MT, about 153k miles.

I'm experiencing very noisy cold starts-- it's a long story, so I've posted the Cliff's Notes version here, and I'll put the extended version below. Read whichever you have time for, please provide any feedback or suggestions.

Short version: After an emergency timing belt repair I have a very loud cold idle noise issue. Noise goes away with increased revs. After engine is at operating temp the engine sounds pretty much normal. Noise could be described as a loose, clatter-y sound. If I had to localize it I would say it comes from the front, or front drivers side.

[ultrasonic]

Long verion, w/ background: A few weeks ago my significant other was driving my 91 SS. She called to say that the car was making some noise-- a thunk when pulling away from a stop light, and generally more noise than usual. She also reported that it felt sluggish on acceleration. They were in a safe part of town so I told her to park it and I'd come check it out.

Upon arrival I opened the hood and found a broken AC belt, but there was a little surface rust on the tensioner pulley so that probably happened earlier. The broken belt was still in the bottom of the engine bay, sitting on the upper side of the Primitive skid plate.

Everything else looked ok, so I started it up. Sounded like a very squeaky accessory belt, but otherwise seemed ok. Temp gauge: ok. Idle: ok. etc. So I swapped her and my son over to the 94 Touring Wagon and let them follow me home.

Noise increased over the 3 or 4 miles back towards the house, eventually getting pretty bad, and almost home the engine stopped. No pop, bang, lurch, grind, etc. Just stopped. I coasted it down to a safe parking lot and noticed a little smoke and a burning smell from under the hood. No flames, no other visual indication. After I dropped the family at home I went back w/ tools to investigate. My best guess was that the timing belt tensioner or idler pulley seized, breaking the t-belt. Removing the top two bolts from the driver side timing belt cover I could see the belt was obviously loose.

Next night the car was towed the remaining 1/4 mile to my carport and I dug into it. Radiator drained and removed, crank pully off, t-belt covers removed. The toothed sprocket had seized and snapped off, plastic belt covers were melted through in spots, and there were metal bits and bearings all over the place. Timing belt was fused to the broken toothed idler. Luckily, the toothed idler is mounted on the water pump, so I didn't have to mess with removing the broken bolt, etc.-- just replace the pump.

I ordered an aftermarket timing belt kit on ebay. I know, it's a cheap-skate way to go, but budget is very tight right now and the rust issues on this car will probably bring it down well before another t-belt is due. And if(when) the EJ22T is moved to another chassis it should get a full service at that point anyway. I installed a new OEM water pump, thermostat, and gaskets.

I had done a t-belt service just about 30k miles ago, so I figured the tensioner would be ok to reuse. I built a jig using a 2x4 and a large C-clamp, and slowly compressed the tensioner over the course of a couple hours. Everything from the t-belt kit was installed (toothed idler, tensioner pulley, timing belt) but the two smooth idler pulleys wouldn't work. The stock mounting bolts would bottom out before tightening up, so I re-used the original ones as they spun smooth and quiet.

I left the AC belt off because the tension adjustment pulley had seized. That's what broke the belt, and I don't think it was related to this incident.

Reassemble everything, top up the fluids, etc. Turn the key and it lights up the first time. But it's noisy, REALLY NOISY. Like a diesel truck. I shut it off, checked everything. It all looks ok. No leftover parts, plenty of oil, etc. I fire it up again, let it idle while topping off coolant. Still noisy and I discover that the noise goes away as the revs build-- spin it up to about 2000 rpm and it sounds normal. Ok. Take it for a gentle test drive. Everything feels fine, and after a few minutes the engine is at normal temp and the idle noise is gone. I've been driving it a little and the symptoms are very consistent. After it warms up it runs beautifully. I've avoided really laying into it, but it's running fine in commuter cruise driving.

I figure there are two likely explanations:

a. The infamous EJ piston slap.
b. Collapsed, or partially collapsed, timing belt tensioner.

Does anyone have any diagnostic suggestions or other comments?

[suba]

What weight oil are you using? And how long did it sit between when it was last shut off and you got it all back together and started up? I know in my 90 if it sits for a few days with out being driven, even in the summer, on startup I get tons of lifter noise. For some reason I get the most noise the day after an oil change, but after it was run, and then the next day it's fine.

[Buffman]

I might have to say the tensioner is bad. I had a knock on my driver's side of the front of the engine that happened after long drives. i pulled power to injectors one at a time, and discovered it wasn't rod knock. When I did the timing belt (cam seals were leaking), the stock tensioner pulley was still on there, and while it spun smoothly, it wasn't the quietest. After taking the tensioner out, I thinnk I took like an hour to compress mine. It appeared original, and was a bear to compress it. Before I pulled the pin out to release it when reinstalling it, I took a screwdriver and pushed the unit as close as I could to the pulley before tightening the bolts and pulling pin. Noise in my car is gone.

[ultrasonic]

...
I know in my 90 if it sits for a few days with out being driven, even in the summer, on startup I get tons of lifter noise
...

I've put enough miles on "vintage" Subarus to know lifter noise when I hear it. This is way beyond lifter noise.

[fishbone79]

I'm beginning to think that you and I have a very similar issue, ultrasonic. Mine began sometime after I changed the timing belt last summer and did not replace the idler bearings (thinking I'd wait till this year since I was low on cash then).

If I drive the car every day, the noise only appears after the motor is well warmed up, but it's a persistent tick-tick-tick thats much louder than any lifter I've ever heard.
The only time it gets worse is on a cold start when the car has sat for something on the order of a week... then it sounds almost exactly like an old pushrod V8 with a stuck tappet... clack-clack-clack. Loud as hell. The car's sat for the past week and I only fired it up today. The noise also goes away with RPM, probably disappearing somewhere above 1800-2000 or so (can't see the tack when I'm twiddling the throttle under the hood).

I bled/replaced all the HLA's and have since replaced the idler gear, bearings, and tensioner bearing. I did not replace the tensioner itself, but it seemed fine when I compressed it over the course of about 30 minutes. Since replacing the idler bearings the noise is a bit worse, so I'm beginning to wonder if maybe you're right about it being the tensioner, buffman.

Here's my previous post about it: http://bbs.legacycentral.org/viewtopic.php?p=293517

I've been chasing this damn noise for nearly a year now... I know it's not bottom end or piston slap (that sounds much different, this is harsher), and I've played the screwdriver stethoscope game and it does seem to be noisiest around the driver's side head, but could also been in the front of the motor. I'm fairly sure it's not valve related as I cannot isolate the noise to a particular region of the drivers side head. Maybe when I'm back up to stuff I'll make sure the timing belt is tighter than a nun's navel before I release the tensioner.

[ultrasonic]

Stripped it all down again last night: rad drained and removed, belts, crank pulley, t-belt covers. Removed timing belt, idlers, and tension adjuster. Compressed adjuster, reinstalled it along with the belt and idlers. Moved adjuster to the left and torqued the mounting bolts, pulled the pin. Every thing went together ok. There appears to be a bit more slack in the belt than I remember from the previous times I have installed t-belts, but I can't say for sure. Otherwise it all looked ok as I put it together.

Topped off fluids and started it up-- still noisy.

Spent some warm up time this morning in the driveway checking fluid levels and looking for coolant leaks. Then I drove it to work. By the second or third stop light the noise had subsided, just like before.

[Buffman]

interesting.