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Author
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Topic: Rod Knock on startup?
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Stimson
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Member # 51
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posted
 
 
I recently switched to 20-50w and have been getting a few seconds of rod knock at startup. This is about half as much rod knock as I hear after I install a new oil filter, so its not too bad. Any other 5.O owner out there have this problem? I haven't changed my oil in a really long time, and its probably thicker than need be as well.
Posts: 2373 | Registered: Jun 2000
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JohnB
Tech Moderator
Member # 969
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posted
I would go with a "weak" lifter before I called it a rod knock. If changing the oil causes a knock like that, I'd definitely consider parking the car. ![[Smile]](smile.gif)
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1965 Shelby Cobra
1993 Cobra
2012 F150 Raptor
2020 GT500
Posts: 6523 | From: Orlando FL/Redding CA | Registered: Mar 2002
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Stimson
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Member # 51
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posted
I technically didn't change the oil..... I burn a quart of 10-30 every 500 miles. Last time I had a fresh filter and oil on there was in January. I've recently started pouring in 20-50w instead..... figured all the 10-30w has burned out by now.
Weak lifer? How can I diagnose that? The knock seemed to have started after a spirited drive through the moutains.
Posts: 2373 | Registered: Jun 2000
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JoeT
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Member # 298
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posted
I have a cherry shortblock on a motor stand that has cool rod-knock at startup. I'll trade you straight up ![[Big Grin]](biggrin.gif)
How's your 'hot' idle oil pressure?
Posts: 6785 | From: San Jose | Registered: Jun 2001
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Stimson
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Member # 51
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posted
Durring cruise its as high as the stock guage can physically read (a tad above the half way mark), at idle its at the 1/4 of the way up mark.
Posts: 2373 | Registered: Jun 2000
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JohnB
Tech Moderator
Member # 969
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posted
A quart every 500? Ouch... ![[Frown]](frown.gif)
A weak/bad lifter is pretty easy to find. With the car cold, pull both valve covers and push down on the tops of the rocker arms..the bad one will show itself quite easily. It'll probably be the only one you CAN get to compress.
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1965 Shelby Cobra
1993 Cobra
2012 F150 Raptor
2020 GT500
Posts: 6523 | From: Orlando FL/Redding CA | Registered: Mar 2002
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Stimson
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Member # 51
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posted
Thanks for the tip. I also heard this trick for figuring out what rod is knocking:
Pull the spark plug on the suspected cylider/piston/rod that is knocking. If the sound goes away, you found the rod that is knocking.
I think my baby is just thirsty for some of that home cooked mobil 10-30w. At 240K miles, a quart every 500 miles isn't too bad
Posts: 2373 | Registered: Jun 2000
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JohnB
Tech Moderator
Member # 969
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posted
Ya, you can try the spark plug wire trick too- just remember to put it back on!!
At 240k, I think we here on the board need to start a "Sawson needs a new engine" fund. ![[Wink]](wink.gif)
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1965 Shelby Cobra
1993 Cobra
2012 F150 Raptor
2020 GT500
Posts: 6523 | From: Orlando FL/Redding CA | Registered: Mar 2002
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Stimson
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Member # 51
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posted
Who knows..... I was really hopping to hit the 300K mark though, but I guess I've had one too many 5800 RPM shifts and one too many spirited drives through the mountains to reach my goal Even if thinner oil and a new oil filter doesn't make the rod on start up go away, I still think I can drive her for several thousand more miles just fine. If a new motor does get dropped in there, it will be a junk yard Explorer 302 and I won't have time for such a project until winter break
Posts: 2373 | Registered: Jun 2000
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Copello
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Member # 1534
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posted
thats what you get for not changing the oil, adding oil doesn't make up for a dirty filter, my 88 gt use to make noise on startup after it sat for a while and I used 5w30, your rod nock might be piston slap.
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91 GT
73 RS Camaro
Posts: 1309 | From: San Mateo | Registered: Jul 2002
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Stimson
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Member # 51
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posted
Good point. It could very well be piston slap. I know my rings have very low tention due to my compression numbers vs my leak down test numbers. What do you guys know about piston slap? As for my oil & filter, its not that old.... ~6,000 miles. Not too far out of Ford's specs.
Posts: 2373 | Registered: Jun 2000
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Stimson
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Member # 51
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posted
fyi: After checking out a few cold starts today I don't think its rod knock. The frequency is too fast. It maybe something rattling against the exhaust/block/bellhousing.
Posts: 2373 | Registered: Jun 2000
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Gear Head
JARED
Member # 779
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posted
Sawson how do you motor mounts look?
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Support our troops!
Posts: 5685 | From: EASTBAY | Registered: Jan 2002
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BlackNGold
CaliforniaFords.com
Moderator
Member # 655
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posted
Sawson~Save your money on oil and buy a GT40P/Explorer 5.0!!!!.... ![[patriot]](graemlins/patriot.gif)
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-SLOWER TRAFFIC KEEP RIGHT-
Posts: 5132 | From: Bay Area, CA | Registered: Dec 2001
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91 5.0
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Member # 1527
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posted
quote:
Originally posted by JohnB:
A weak/bad lifter is pretty easy to find. With the car cold, pull both valve covers and push down on the tops of the rocker arms..the bad one will show itself quite easily. It'll probably be the only one you CAN get to compress.
Unless the bad lifter is on the raised part of the camshaft lobe. Might have to spin the motor around a few times to find the bad one. ![[dance]](graemlins/dance.gif)
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02 GT - Zinc Yellow
91 5.0 LX - Red
Posts: 1316 | From: Fairfield | Registered: Jul 2002
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Stimson
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Member # 51
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posted
This morning it started up fine. I'm starting to doubt its rod knock now ![[Whoo Whooooo!]](graemlins/woowoo.gif)
Will she live to see 300,000 miles? ![[Eek!]](eek.gif)
Posts: 2373 | Registered: Jun 2000
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Primer GR40
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Member # 476
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posted
quote:
Originally posted by st5150:
This morning it started up fine. I'm starting to doubt its rod knock now
Will she live to see 300,000 miles?
no
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Superdupercharged Cobra
No Transmatic Notch
Posts: 2108 | Registered: Sep 2001
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JoeT
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Member # 298
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posted
I'm thinking no as well.
Posts: 6785 | From: San Jose | Registered: Jun 2001
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Stimson
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Member # 51
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posted
What ever the sound is seems to be doing it more if the car has only sat for one hour. It runs kind of rough for the first ~20-30 seconds, making this odd sound and then acts fine.
Only reason it won't hit 300K miles will be because I'll graduate and do the job/house/spend money on the car thing around the 270K mile mark
Posts: 2373 | Registered: Jun 2000
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street_illegal_stang
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Member # 1554
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posted
man...just change your oil.
i work at a jiffy lube.to bad i live in so cal..i totally hook up you and shady joe for free..
i don't wanna try to sell you on a product
but fedell castrol 20W50 hi mileage works great
that stuff is thick ![[worship]](graemlins/worship.gif) ..if you take it easy on your 200k+5.0 i'm sure you'll make it to 300k easy mind you no higher than 4200rpm..
damm.good luck
Posts: 1276 | From: Long Beach C.A | Registered: Jul 2002
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street_illegal_stang
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Member # 1554
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posted
quote:
Originally posted by st5150:
What ever the sound is seems to be doing it more if the car has only sat for one hour. It runs kind of rough for the first ~20-30 seconds, making this odd sound and then acts fine.
Only reason it won't hit 300K miles will be because I'll graduate and do the job/house/spend money on the car thing around the 270K mile mark
wow..you really bring my hopes up to buy a cheap
$1200 mustang with 217kmiles
Posts: 1276 | From: Long Beach C.A | Registered: Jul 2002
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