1994 Olds Silhouette low rpm engine knock ?

[striaght razor]

Hello All,

My son has a 94 Olds Silhouette with a 231 engine, that has developed a low rpm engine knock. It is very loud and disipates when the rpms go up. This engine also has a frozen ac compressor and a smaller drive belt has been put on to avoid the frozen ac compressor. This was done before we took ownership of the vehicle.

With the engine running we put a wrench on the idler pulley and rotated counter clockwise to relieve the tension on the belt and the knock went away. Thinking that it was the bearing in the idler pulley, we then replaced the idler pulley and belt with new parts to find that the knock was still there.

I suppose by relieving the tension on the drive belt that the pressure was also off of the alternator, water pump and power steering. We did take the alternator off and had is checked, the bearing and output is fine. The car is also not over heating, nor is the water pump pully running wobbly. There also are no power steering problems.

The speed of the knock does increase with the speed of the engine, however, when the rpm reaches a certain level the knock goes away....

At this point we would appreciate any assistance you might offer.

Thanks in advance for your assistance....

Sincerely, Straight Razor....

[maxwedge]

Originally Posted by striaght razor

Hello All,

My son has a 94 Olds Silhouette with a 231 engine, that has developed a low rpm engine knock. It is very loud and disipates when the rpms go up. This engine also has a frozen ac compressor and a smaller drive belt has been put on to avoid the frozen ac compressor. This was done before we took ownership of the vehicle.

With the engine running we put a wrench on the idler pulley and rotated counter clockwise to relieve the tension on the belt and the knock went away. Thinking that it was the bearing in the idler pulley, we then replaced the idler pulley and belt with new parts to find that the knock was still there.

I suppose by relieving the tension on the drive belt that the pressure was also off of the alternator, water pump and power steering. We did take the alternator off and had is checked, the bearing and output is fine. The car is also not over heating, nor is the water pump pully running wobbly. There also are no power steering problems.

The speed of the knock does increase with the speed of the engine, however, when the rpm reaches a certain level the knock goes away....

At this point we would appreciate any assistance you might offer.

Thanks in advance for your assistance....

Sincerely, Straight Razor....

They key to this whether the noise is internal or in the pulley system, remove the belt completely and see if your knock is gone, engine hot. You can run it this way for a few minutes, if gone focus on the water pump or the harmonic balancer, they( the balancer) can come apart at the inner and outer hub area.

[striaght razor]

Hi Maxwedge,

Great call on the Harmonic Balancer. It was a little nasty coming off, even with the wheel puller and the vent removed from the fender, but the new one went right on and the knock is gone.....

Thanks very much.....!!!

Rgds/Straight Razor....

[maxwedge]

Originally Posted by striaght razor

Hi Maxwedge,

Great call on the Harmonic Balancer. It was a little nasty coming off, even with the wheel puller and the vent removed from the fender, but the new one went right on and the knock is gone.....

Thanks very much.....!!!

Rgds/Straight Razor....

Good work.