Tahoe & SuburbanThe power, space, and brutal towing ability make the Tahoe and its longer sibling, the Suburban, arguably the best full size SUV's on the market today.
Platform: GMT 400, 800, 900
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Here is the short story... mother n law went 15,000 miles with no oil change (said she was waiting for the oil life to hit zero on the dash). During this event she said the motor was ticking. Every time she brought the car over it would not make any ticking noise. I thought she was imagining things. Well one day she brought it over and it was definitely making a ticking noise. Almost like a noisy lifter or a rod knock (soft rod knock). It was coming from the drivers side and sounds like top end. I freaked out when i heard the noise and thought the motor was blown. Then the noise magically disappeared... nothing... super quiet clean idle.
So i have been driving the car for a couple days trying to figure it out. After a good oil change i put some seafoam in the crankcase which seems to have quietened down the tick. It would not tick while just sitting idling but would start after about 10-15 min on the freeway. After it started it would stay ticking for about 5-10 min... whether parked or still driving on the freeway. The noise is not super loud, if I have the radio on you can barely hear it. Low idle, high idle, revving the motor or even shutting off the motor the noise would not go away for about 5-10 min... After the noise went away for the first time I have never heard it come back, unless i park, let it sit for 30 min and then go driving again, after about 15 min on the freeway the noise would come back and go away after 5-10 min.
So i searched for a long time and decided to run a little atf in the motor for a few days but that did not help, actually it seemed to make the noise happen even more often but still only while driving on the freeway (never at idle). I thought it might be sludged up on the top end so i pulled the valve cover, pulled all the rocker arms out, cleaned the push rods, and sprayed brake cleaner through the push rod into the lifters. While i was in there I found nothing unusual and everything looked very clean. After I cleaned everything and put it back together I let the motor idle for about 30 min, no ticking... yay!!!
So i changed the oil and switched to mobile 1 syn and added 1 quart of lucas treatment. I let the motor idle while I was cleaning up and it sounded good... but then after about 10 min of idling the noise started up... it has never made the noise while just sitting idling. I have always had to drive on the freeway to start the noise. I decided to see what happens if i rev the motor and the noise went away right away. Thought it was a fluke but about 5 min later while idling the motor started ticking again. After a quick rev the noise went away.
I am very confused and I am tired of searching the web (my eyes hurt) so i thought I would ask here.
By the way... motor has 118,000 miles, no leaks, runs great, noise does not affect drive-ability, oil pressure sensor is working and reading correct pressure (just above or below 40 depending on rpm). Noise does not seem to be getting louder and has been around for a few months
Anyone have any ideas???
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Cam will in general turn twice as fast as the crank.
I believe the cam turns at 1/2 crank speed since the crank timing gear is smaller than the cam gear.
The way I check is by idling the engine down as slow as it will go and then count the ticks for about 15 sec and multiply by four. If the answer is the same as the rpm, then it's at crank speed. If half rpm, then cam speed. Helps narrow down the area it's in. One exception is piston slap which usually occurs on power stroke which would also be at cam speed. But piston slap is usually noticeable at cold and goes away as engine warms up and piston expands.
2010 Sheer Silver Tahoe LTZ (all options but sunroof, power boards), GM (body color flaps, rear console, 3rd row mat, 2-Way Remote, chrome gas door, Esky rack), Eagle Eye LED tails, SLP dual tip exhaust, Silver bow-ties/rear wiper, Catch-All mats, AlphaTherm washer fluid heater, Putco chrome mirror covers, silver calipers, board chrome trim, tint, GMPP Major Guard
A 1 1/4 inch dowel rod about 2-3 feet long placed on the engine and next to your ear can do wonders for hearing the engine... exercise caution when placing it near the belts...
harbor freight has mechanic's stethoscopes for about $5 I have never used them and have always done a dowel rod but, either way you may be able to narrow the tick down to a cylinder that way...
It could also be an ever so slightly loose rocker arm....
well i was hoping to get a little more feedback before I tear into the motor...
I just went on a long road trip with the car and i wanted to add a little more info
The motor does not tick upon start up (even on the coldest mornings and sitting for days)
But after it warms up and only at freeway speeds it will start ticking after about 5 min of being on the freeway. The ticking will last for about 10 min and then go away. We drove for 5 hours straight with no ticking. Got to our hotel and did not drive for a few days. Left to come home and did the same thing on the way home except when we stopped for food, drinks, and gas and got back on the freeway after about 5 min it starting ticking and then went away for the rest of the drive home.
I have stopped the car at idle after it happened and because of the speed and location of the tick have determined it is coming from the top end. It is not an exhaust leak, and i have checked all the push rods and rocker arms.
Does anything turn on/off of open/close in the motor after driving for a few minutes at high speeds (i know that might sound like a stupid questions but I am trying to figure out why it only does it once after getting on the freeway for about 10 min)???