I think I broke my truck ...

[czarcaustic]

Hey guys. I had to really pour on the throttle the other day in a situation on the road, after slowing back down to normal cruising speed I noticed a new noise from under the hood. It was almost a ticking or scraping sound that increased and decreased w/ RPM.

I have attached a crappy (dark and iphone) video to hear the sound. I have also noticed white smoke out of the tailpipes now ... which was never an issue.

Any suggestions as to what I may have done? I can't tell any real difference in power ... but the noise and smoke are definitely new.

Old engine sound no smoke:

1971 GMC C1500 Longbed - YouTube

New engine sound w/ smoke (loud - turn speakers down):

whoops - YouTube

[Sillyoldman]

Hard to comment on the videos. I'd yank the valve covers first and check out whats happening under them.

[rogergodding]

Yeah, pull the covers and check those rockers.... I had a great sounding engine with a lopey cam several years ago.... got on the throttle and one of my lifters seized up, inside the block, shaved my cam down a bit.... shortly thereafter was a knock coming from the crank......

[70cst]

Good luck. Hope it isn't serious

[IntegratedTJ]

From my experience, a blown head gasket could be the culprit. Also could be worn out rings but I'm not sure it'd come out of nowhere all at once. But as the others said, check what's easy to check first. Good luck. Post back with results, would be good to know for possible future situations.

Edit: Just watched the video, that sound is pretty nasty. Hope all is well. Doesn't seem like any of the two things I suggested. Hope it works out well, man.

[Already Gone]

You have a very nice truck. I cant help you with your noise problem but will say what ever it is it's worth fixing. By the way your rims look super.
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[leddzepp]

With the white smoke I'd say a blown head gasket. Check your radiator to see if the level has dropped. Sounds like a scraping noise as opposed to a knock, as suggested above pull the valve covers and check things out.
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[czarcaustic]

Thanks for the responses everyone. I don't have much time to tear into the engine this week ... so it looks like Marilyn will need to sit under the carport until I can get to her this weekend. I cranked her up again last night, to see if I could better diagnose the location of the noise and it sounds even worse/louder. I don't want to fire it up again until I can locate the issue.

Bummer. Ruined my pretty decent week.

I will keep everyone updated.

[czarcaustic]

Neighbor talked me into starting it up one more time so he could hear it. He is of the opinion that it isn't internal (not a knock or ping as he said). He thinks it is likely a pulley bearing, hence the 'scrape' sound. The white smoke is something he didn't seem too concerned about with an engine this old ... since it isn't "pouring out or anything - obviously you should fix whatever is causing it, but I don't think it is necessarily related to the noise".

He knows more than I do about engines. Does that sound plausible?

[cleszkie]

Not to piss on what your neighbor told you, but if that white smoke just suddenly appeared, then you just suddenly got a leak in your water system, and that needs attention. As others have said, could be a head gasket which will rapidly get worse, or it could be something worse like a cracked head or block. Check your oil to see if you have water in it before you run it again. Good luck.

[czarcaustic]

Originally Posted by cleszkie

Not to piss on what your neighbor told you, but if that white smoke just suddenly appeared, then you just suddenly got a leak in your water system, and that needs attention. As others have said, could be a head gasket which will rapidly get worse, or it could be something worse like a cracked head or block. Check your oil to see if you have water in it before you run it again. Good luck.

No no - I understand. I know you aren't pissing on the neighbor. I am all about differences of opinion so that I know how to diagnose and potentially fix this issue. All information, properly filtered, is good information (if not now, then possibly later.)

I agree that the smoke is something that needs to be addressed.

[mmiddle]

Yes, I think the scraping sound is external. The smoke could be bad valve seals that where wiped out under high WOT vacuum. It is hard to say by just a discription of the events and a low quality video.

I would pull the belts off and closely check all pulleys and bearings AND the crank balancer and pulley. It could also be the input bearing on the trans.

the smoke is a nucence but only tell-tells a tired motor that needs refreshed at some point in the future.

[mmiddle]

And yes, you do need to confirm that this smoke is oil or coolant. Oil = tired motor. Coolant = head gasket or crack that needs fixed now.

[Bigdav160]

The noise sounds like the compressor clutch.

The "smoke" could be normal water vapor from combustion.

Does it get worse as the engine warms up or goes away?

[czarcaustic]

Again - thanks for all of the suggestions guys. I will jump into a full-on diagnosis this weekend and report back.

Lunch is over and it is now time to head back to my day job. LAME!

[chevyman95]

Easy way to tell if it is a pulley is take off the belts and crank it up for a few seconds and see if the sound is still there. I've never done this with one of these trucks but it helped me isolate a noise on my 04 GTO. Don't run it more than a few seconds though because you don't want to overheat the truck

[Coley]

I'm kinda' with BigDave on this one....with respect to the compressor clutch.
Start by disconnecting the a/c belt and see if it continues.
After that disconnect all the belts one at a time....and re-check the engine for sounds when running. Be careful not to overheat the truck with the water pump disconnected.
If it is the a/c compressor-clutch or the water pump or the alternator...removing the belt from that accessory will quickly identify the problem.
Put a timing light on it to see if you have an extremely 'scattered' timing signal....ie: if your timing chain was extremely loose, rubbing and possibly going to let go...it would probably show up with the timing light.
Also, check both your oil and radiator to see if they still look uncontaminated from either liquid...this would be a possible sign of a blown head gasket or a coolant/passage failure or similar.
Good Luck, keep us posted.
All Good
Coley