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Clunking and knocking when starting up


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Thought it would be a good idea to take advantage of this snow we have here in Portland, so I went drifting around my high school parking lot with some friends and was pushing my Comanche pretty good. We stopped walked around for a bit and when we were leaving, I started up my Comanche and it made a god awful knocking sound starting up, but when it started, it ran just fine. The oddest part is that it sounds like the engine is gonna fall out when starting, but it drives just fine no problem. So I am a little worried I pushed her too hard and damaged it.

Here are the specs:

-1986 Comanche Custom

-2.5L engine

-Torqueflite 904 3 speed auto

-Can’t think of anything else to put at this moment as I am a little worried.

 

All help will be much appreciated, Thank you!

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Check your oil level? If you've got an oil pressure guage, what does it read during cranking/startup. Also is the noise only while you're on the starter or does it keep making it after you let go of it?

Other things to check would be motor mounts, trans mount, and also the bolts between engine and trans. Could be exhaust banging around, frankly could be anything really... Anything loose could be making a knocking sound. 

See if you can get someone to have a listen in the engine bay, or start it while you're listening, to see if you can isolate it to any part of the vehicle. Just keep away from belts, fans, and other moving parts. 

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Noise only happens when on the starter, after it starts up and let go of the starter it runs fine. Also the noise definitely sounds internal and everything else looks solid, my Jeep only has 100k miles on it so I don’t think anything would be too worn out, but then again it’s a Jeep. As for the oil pressure, I am waiting for my dad to get home so he can also listen to it as well. So I will post my oil pressure once my dad gets home and we can both hear it together. Thanks!

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Your flywheel/flexplate might be all chowdered too.  Pull the starter off first and look at the bendix drive on it and then look at the flywheel teeth.
 

Also could just be that the starter bolts are coming loose and it's not engaging right anymore.

 

Otherwise I'd say just don't buy the cheapest reman.

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I don't know if this applies to the 2.5L, maybe someone could chime in, but the 4.0 starter bolts aren't the same size. One's metric and the other isn't. They're very close, so it might not be obvious they're cross threading. 

 

I've had starters make tons of racket. Once because the starter bolts were loose, once because the engine to bellhousing bolts were loose/missing so the starter and dust shield were effectively the only things holding the engine and trans together...

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Timing chain tensioner in my 220,000 mile motor sounds horrible on start up.
Loose starter or cracked drive (I switched to a TJ starter and mine cranks like a 24 volt system now.
Crank position sensor loose is an issue. I have the 2.5L TBI flexplate in my stuff but I’m going to switch to 4.0L instead but I considered a 700R4 from a 2.8L S10 Blazer with np231 or np242 tcase.


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15 hours ago, NCardwell said:

Yea, crawled under my Manche with a foot of snow and found that one of the starter bolts came completely loose and was resting on the exhaust, thank god for the exhaust! Bolted her back up and it’s starting fine, thanks guys for the help.

 

Confucius says don't ask questions until you physically eyeball the problem area.   :thumbsup:

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  • 3 weeks later...
Thought it would be a good idea to take advantage of this snow we have here in Portland, so I went drifting around my high school parking lot with some friends and was pushing my Comanche pretty good. We stopped walked around for a bit and when we were leaving, I started up my Comanche and it made a god awful knocking sound starting up, but when it started, it ran just fine. The oddest part is that it sounds like the engine is gonna fall out when starting, but it drives just fine no problem. So I am a little worried I pushed her too hard and damaged it.
Here are the specs:
-1986 Comanche Custom
-2.5L engine
-Torqueflite 904 3 speed auto
-Can’t think of anything else to put at this moment as I am a little worried.
 
All help will be much appreciated, Thank you!


Also make sure your starter bolts are stock knurled ones and not something slapped in there. (Mine were when I got my truck)


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