Belts keep slipping

subaru
legacy

#1

The timing belts keep slipping on my car. I replaced the belts but it keeps happening. I went to readjust the belts today and noticed the pulley looks off. I know it needs to be replaced but given that it’s the bott one under the radiator hose I’m not sure if it’s one that I can easily do myself or if it would be better to have a mechanic do it.


#2

I can see by the photo how loose the belt is. And, frankly, that doesn’t look like the correct belt for the application. The belt should engage all of the V-grooves across the pulley.

I’d suggest taking it to a reputable independent mechanic for a look-see. It shouldn’t be cost-prohibitive to get the right belt installed to the proper tension… and get the tensioner checked too.


#3

wrong belt…


#4

The belt was loose because I had loosened it to take the belts off. My concern is that the pulley seems to be sliding back somehow. This is the bottom pulley where both belts loop around. The way the pulley is sitting now some of the grooves on the pulley are blocked. If you look on the bottom of the picture you can see the metal is overlapping the pulley and it’s the same way on the other side.


#5

The crankshaft pulley/harmonic balancer has failed. The rubber between the center hub and the outer pulley is gone, that is what was squealing. The car will need to be towed.


#6

[quote=“Nevada_545, post:5, topic:94932, full:true”]
The crankshaft pulley/harmonic balancer has failed. The rubber between the center hub and the outer pulley is gone, that is what was squealing. The car will need to be towed.
[/quote]Exactly!

BTW, those aren’t timing belts. They are serpentine belts. The timing belts are behind the timing covers.


#7

I would get this towed unless your mechanic is less than a mile from your house.

Driving with that belt this loose will not turn the water pump and you will quickly over heat the engine doing major damage well over $1000.

It could be that you do not have the belt routed correctly. Any parts store or a dealership should be able to print you off a copy of how it is routed.

Yosemite


#8

The Gates online manual will also show the proper routing.
However I still believe it’s the wrong belt. Serpentine belts are thin to be able to go around small diameter pulleys in both directions, but compensate by being wide to maintain their strength, and contacting a wider pulley interface with V-grooves (which increase contact area) for better traction. This belt is clearly too narrow for the pulley IMHO.

Those who suggested that the harmonic damper is shot may be right, but normally symptoms for that would include engine shaking. The damper sandwiches a rubber energy-absorber between the crankshaft and the pulley. When the pulse is felt by the piston being pushed down, some of the rotational energy is absorbed by the rubber and released into the damper’s mass and the pulley system out of phase with the pulse, dampening the effects. When the rubber in the system deteriorates, the engine normally starts shaking.


#9

The pulley has two areas, and the belt in the picture matches the inner, narrower pulley area. Serpentine belts can be as narrow as four grooves.

@nikww, the pulley appears to be wearing away the timing cover. Do NOT run the engine, or you risk further damage to the cover with every turn of the crankshaft.


#10

Hopefully the OP will get it checked out and you’ll turn out to be right. If so, lunch is on me! :grinning:


#11

When a vehicle has more than one serpentine belt, the one(s) powering just one accessory are usually narrower than the main belt.


#12

True, but the one in the photo is on the wider portion of the pulley.
Hopefully the OP will post when he/she gets a definitive diagnosis and answer.


#13

Yep, and he/she explained it was because the belt was loosened. Regardless, the harmonic balancer needs to be replaced before the engine is started again.


#14

Perhaps. But, without engine shaking symptoms, Id’ try checking the damper by trying to shake it with my hand with the belt removed before deciding it was bad. A bad damper will feel loose.

I guess we’ll both find out together when the op posts back.


#15

The pulley looks like it’s pushed back from the front of the assembly and now appears to be cutting into the timing cover.


#16

You may be right. Hopefully the OP will post back.


#17

There could be an engine vibration if the engine is externally balanced but that is unlikely. This damper absorbs torsional vibrations for crankshaft durability, this would not noticeable by the driver of the vehicle.

BTW the rest of us are looking at a picture of a crankshaft pulley with half of the inside belt area buried inside the timing cover, that is where the belt once tracked.


#18

If you’ll allow me to go a little off topic, an article in a magazine said that a defective damper (harmonic balancer) can adversely affect engine timing w/resulting engine performance degradation. Is this actually the case? What’s the mechanism a defective damper would affect ignition or valve timing?


#19

The timing mark on the pulley will be in the wrong place giving you the wrong TDC reference when setting the timing on an old car. There is generally no reason to tamper with the timing on most cars, if it is even possible.


#20

Ok, that makes sense. If the damper has twisted enough the manual timing adjustment could appear correct by the timing light on the damper, but not by the actual position of the piston.