First Generation Firebird
Posted By: spoonymac Grinding sound after 5 minutes idling - 11/29/21 06:39 AM
I have a 1968 Firebird 400 with a 402 bbl.
I backed it out in my drive and left it idling while wiping it down. After approximately 5 minutes I heard an awful grinding sound with smoke coming the engine. I immediately turned the key off popped the hood and found a small oil spatter on the passenger’s side top of the firewall.

This one is a mystery because after further visual inspection there are no leaks and nothing looks broken.

I did see a drop of oil at the bottom of the starter. I mentioned this because the starter sometimes does not engage and when turning the key, It sounds like it just spins and grinds but it does engage after a second attempt.

I do suspect the starter; however, where did the fresh oil spatter come from?

I’m hesitant to try to start it again due to causing further damage.
Posted By: barnbird Re: Grinding sound after 5 minutes idling - 11/29/21 06:22 PM
This is the type of thing that needs in person diagnoses but I can steer you a little. If you're lucky the noise was from a bad alternator or water pump bearing and the smoke was from a belt. remove the alternator belt, spin by hand and listen and feel for bearing roughness. For water pump do the same as well as grab ahold of the fan and try to rock back and forth, if it has play replace. I suppose it could also have been the starter hanging up but doubtful and the smoke component would not be there. As far as your starter problem this is either caused from it being improperly shimmed, a bad solenoid, or teeth being chewed up on the Bendix gear or the ring gear/flex plate or both. It takes further diagnosis to figure out.
Posted By: spoonymac Re: Grinding sound after 5 minutes idling - 11/29/21 06:54 PM
@barnbird - Thanks for the info.
I'll give a full update - probably by this weekend.

Thanks again.
Posted By: barnbird Re: Grinding sound after 5 minutes idling - 11/29/21 06:59 PM
Good luck.
Posted By: spoonymac Re: Grinding sound after 5 minutes idling - 11/29/21 07:56 PM
WFH is great! I took a lunch break and removed belts from the water pump (no fan attached - electric fans), alternator and AC compressor.
All seems good - no play and spins freely without grind.

The power steering pump does have enough play to hear it knock when I pull on it; however, I did not remove the belt.

We are probably back to starter but you are right why the smoke though could it be the power steering?

FYI the smoke color was light gray and not a lot of it.

Posted By: barnbird Re: Grinding sound after 5 minutes idling - 11/29/21 08:32 PM
A little in and out shaft end play on the steering pump is normal. There should be none side to side and silent when spinning by hand with belt loose. The smell of the smoke would tell you everything you need to know. Rubber=belts plastic=wiring, and burning oil smells just like it does out the tail pipe on a car or even a lawnmower. Also, one thing I forgot to mention about your starter not engaging on the first try is to make sure the two bolts holding your starter in are tight. If the knurling on the shoulders is worn off they tend to loosen over time.
Posted By: spoonymac Re: Grinding sound after 5 minutes idling - 11/29/21 09:09 PM
OK - my next check is to verify loose bolts on the starter.

The grinding noise coming from the starter during startup is intermittent and I have PTSD now when I turn the key.
If the bolts are tight, my next step is to get a new starter.

What is your recommendation on starter?
The current one is a NAPA Premium 1.4KW and it doesn't look like a mini-starter.
The part number is rubbed off on the sticker so I will have to wait until it is removed.

As I said before it's a 396 factory bored 402 and the numbers match a 72 chevelle or camaro.
Posted By: Bob S. Re: Grinding sound after 5 minutes idling - 11/30/21 03:37 PM
You didn’t previously say it was a chebby motor. Way different from Pontiac.
Posted By: spoonymac Re: Grinding sound after 5 minutes idling - 11/30/21 08:54 PM
You are correct.
Posted By: 68tpls400 Re: Grinding sound after 5 minutes idling - 11/30/21 09:47 PM
It's obvious that the car is pissed that a Chebby engine was put in her!
Just her way of expressing her dissatisfaction!
laugh
Posted By: spoonymac Re: Grinding sound after 5 minutes idling - 11/30/21 09:55 PM
LOL.
Probably. I bought rescued her that way.
Posted By: Bob S. Re: Grinding sound after 5 minutes idling - 11/30/21 10:08 PM
When I was 17 I bought a 69 Firebird with a chebby 396. I took the motor out and put in in a 66 impala. I wasn’t allowed to keep the bird so I passed the motorless bird on to a friend
Posted By: spoonymac Re: Grinding sound after 5 minutes idling - 12/01/21 05:41 AM
Must’ve been an awesome friend.
Posted By: spoonymac Re: Grinding sound after 5 minutes idling - 12/11/21 09:25 PM
Issue found.

There’s a toggle switch under the steering column that turns on the AC compressor which was always on.

I setup my phone to record where the noise was coming from. After a few minutes I saw oil spewing from the back of the compressor with that clicking and grinding noise.

I found it by noticing that the clutch was spinning on the compressor as well.

After turning off that switch the noise and oil leak was no more.

The oil at the firewall that I mentioned in the original post was from that compressor.
Posted By: barnbird Re: Grinding sound after 5 minutes idling - 12/12/21 02:42 PM
Glad you found it. did not know you had a/c but that is what I was getting to by having you take belts off and checking the driven accessories. Although not great your finding is much better than having the noise come from the engine itself. Good job.
Posted By: spoonymac Re: Grinding sound after 5 minutes idling - 12/14/21 09:02 PM
Thank you. Your posts surely helped with the discovery.
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