Strange Noises From Front Of Engine

[stroker]

This morning I freaked out when I started my 91 LS.. It made a noise from the front of engine compartment that sounded like an internal Knock or flutter but was external. Sounded like an engine knock or worse but was definitly external like a pully frozen or something like that except that everything on the engine was turning properly with no wobble or anything from any accessories connected to the serpentine belt. I have the usual leaky P/S pump with its occasional whine but keep fluid level up but it sounds too loud (like a clanking?) to be that. Stuck for answers right now and am afraid to drive it but the engine itself sounds normal. Please help ! Bob

[curiousB]

I guess you could disconnect the serpentine belt and run the motor for 30 seconds or so and see if the noise continues. Hopefully that will be silent and normal. If its noisy with no serp belt it could get expensive (water pump or maybe even worse).

Then reconnect serp belt and see if it returns to being noisy. If it is only noisy with serp belt then it has to be either alternator, a/c compressor, or PS pump. Since you have a leaky PS pump maybe you'll get lucky and the noise will be with it and you can fix two problems with one repair.

Good luck...

[SRK]

B's idea of sliding the serpentine belt off is a good one. But if the engine continues to make noise with that belt off, it's more than likely something driven by the timing belt. Shut it off and have it towed to a repair shop, or take it apart yourself. My advice is not to drive it at that point.

[curiousB]

Then reconnect serp belt and see if it returns to being noisy. If it is only noisy with serp belt then it has to be either alternator, a/c compressor, or PS pump. Since you have a leaky PS pump maybe you'll get lucky and the noise will be with it and you can fix two problems with one repair.

Good luck...

p.s. it could also be serp belt tensioner or idler pulley bearings......

[landar]

Being a 91, you can drive it without fear that the engine will be trashed by a timing belt failure. Yours is not an 'interference' fit engine. However, the first thing I would do is figure out the last time/mileage that the t-belt and water pump had been changed. It is very possible that you are due for both(every 90k miles for the t-belt). While it might not be all that comforting, a failure of those components will only leave you stranded, not with extensive engine damage.

I would go after the noise with a mechanics stethoscope but you have to be extremely careful with the probe around a running engine. And don't wear a dangling tie with the suit. Unless its one of those fake, clip-on types. B)

[stroker]

Thanks Landar for the info. Went to dealer and they said it was the fan bracket and want $510. installed. Does that sound OK or too much ? Thanks again, Bobby

[oldskewel]

Thanks Landar for the info. Went to dealer and they said it was the fan bracket and want $510. installed. Does that sound OK or too much ? Thanks again, Bobby

That sounds fair to me. I replaced the fan bracket on my '91 earlier this year. The fan bracket contains the bearing that the fan pulley runs on. It is that bearing that has failed. I think I paid around $120 for the Chinese non-OEM version (I needed to leave on a trip and could not wait for the real one), and had to machine it a little to make it fit. The OEM one costs around $200, I think.

To replace it requires removal of tons of stuff. It seemed like I was half way to a T-belt job. So their $510 does sound reasonable. Any chance you need a T-belt soon? If so, you might want to consider doing it now. Distributor cap and rotor? Serpentine Belt?

But it's pretty simple work, just removing parts until you can get the fan bracket out. An independent mechanic, or maybe you, could do it. No special tools or secrets required.

[steve2006]

Picture 20 on the link below shows the part that needs to be replaced, all other parts in 1-19 also need removing to get to it!

For the price quoted I would let them do it.

http://www.lexls.com/tutorials/engine/timingbelt.html

[BlackLex]

harmonic balancer? pulley off the crank

[oldskewel]

harmonic balancer? pulley off the crank

http://www.lexls.com/tutorials/engine/timingbelt.html

Those instructions are of course for the full T-belt job, which this is not. When I did mine, I was in a huge rush since I was supposed to be on the road, headed to a snowboard race a few days later and needing to acclimate to altitude. I did feel lucky that the thing broke before I headed out on my trip.

So I basically targeted the fan bracket and figured on the fly which of the steps in those instructions were really needed. Sometimes I figured wrong and had to do a step that I had previously skipped. I had the service manual as well, but that was not really any more useful. There are no instructions there on how to specifically remove just the fan bracket itself, which is unfortunate since it seems they all seem to fail between 150k-200k miles.

From looking through those, and based on memory only, I'd say that steps 1-5 are needed. Not sure about 6. 7 is not. 8-10 are. 11-13 are not. 14-15 are. 16-17 are not. I don't remember for sure but I think I did need to do 18 and 19, but if I did, I did not need any special puller to get the crank pulley off. Note that the T-belt itself and any of the pulleys it rides on are not touched at all when just replacing the fan bracket, although they are exposed. Step 20 shows the fan bracket after all those other parts are cleared away.