Pulse in intake manifold

[grancito]

I'm getting a pulse from #7 cylinder in the intake when the engine warms up, and is bad after hard driving, it roars and runs rough then. I suspect that the exhaust valve is not opening properly, there is a clacking noise in the rocker cover around this area. Anyone had a hydraulic lifter fail, otherwise I think it is a rocker problem at the push rod?

[triplebr1]

hey my buddy has a 93 k3500 with a 6.5 and we had a similar noise and the pulse of air in the intake, it turned out to be a broken valve spring, actualy ended up being 2 broken springs, they were hard to tell that they were broken until we took them out, we just used a fitting to inject air in the glowplug hole to hold the valve up while we took the keepers off and put on the new spring. hope this helps and hope all is ok

[torque454]

I saw a video on youtube of a 6.5 doing something like that he had a broken lifter and bent pushrod.

[grancito]

Thanks triplebr1, Was there a difference with engine temperature, and how much air pressure did you use? Thanks torque454, I hope is is not that problem.

[SCREAMINXL]

Could be a broken plastic rocker arm keeper and the rocker shifted. Better get the cover off. Grant, turn the engine over so that number 7 in on TDC that way if the valve does drop it will land on the piston only a few mm below and still can be retrieved by the valve stem, then apply shop air (i have used 90psi) thru the glow plug hole to hold the valves up. If you dont find broken valve springs or rocker arm keeps the compressed air will tell you if you have a burnt valve due to severe air leakage at TDC. I Wish you the best.

[grancito]

Thanks, I will have to be sure it is at TDC exact, or the pressure will drive the piston down.

[SCREAMINXL]

Just to be safe you can remove the flexplate cover and install vise grips on each side of the flexplate so the engine can not rotate. Wish GM had a crankpin system for the 6.5. Maybe they do?????? At least this way you dont have to worry about exact TDC.

[grancito]

Ok thanks, good Idea, better than removing the head to get the valve back.

[SCREAMINXL]

10 4:) :) :)

[triplebr1]

sorry it took me so long to get back, been sick and out of town, any way i think we used 90psi, but i am sure you could use a lot less, it is only holding a little valve up. just make sure that your compressor is plugged in and ready cause it will leak some. we did not have a problem at all with it trying to turn over the engine, the compression is so high, but the guys all have good ideas, be safe not sorry, good luck

[grancito]

Thanks, I haven´t opened it up yet, just driving slow as am too busy to have it inmobile, but it is ok slow so the oil stays cool, indicates to me that it is a lifter problem. Can the lifters be removed out the top after removing the head, used to do that on the old six cylinder Chev gas engines?

[SCREAMINXL]

Remove rocker arm covers and rocker arms. Mark assemblies so they may be returned to original position during assembly procedure.
Remove guide clamps and guide plates.
Remove valve lifters through access hole in cylinder head using hydraulic lifter remover tool No. J-29834, or equivalent, and a magnet.
Reverse procedure to install, noting the following:
Some engines will have both standard and/or 0.010 inch oversize hydraulic lifters. The oversize lifter(s) will have a 10 etched on the side of the lifter. The block will be stamped O.S. on the cast pad adjacent to the lifter bore and on the top rail of the cylinder case above the lifter bore.
New hydraulic lifters must be primed before installation.
After guide plate clamp bolts are installed, turn the crankshaft manually 720 degrees (two complete revolutions) to ensure free movement of the lifters in the guide plates. If the engine will not turn by hand, one or more of the lifters may be binding in the guide plate.

[grancito]

Thanks very much SCREAMINXL sure beats taking the head off.

[triplebr1]

have you tried lucus heavy duty oil stabilizer? my buddies gas motor had a lifter that would bleed down overnight and then make all kinds of noise in the morning for a few min. after a day of the lucus it stoped and he just puts some of it in at every oil change and keeps driving it, all has been fine since.
just a thought to prevent some work and cost

[grancito]

Thanks triplebr1, I put some lifter additive in incase it is gummed up, but it is bad when the the oil heats up when driving fast. Don't want to thicken the oil too much and cause turbo lubrication problem, but it would help the problem.

[JD_countryboy]

Turbo lube problem? not something i have ever heard about with using Lucaas oil stabilizer. I use it in my truck regularly. Ya right outta the bottle its thick, but dont noice any difference in the oil once drained or on the dipstick. Most everyone i know is using it in all their trucks, cummins big and small, powerstokes, detroits, cats, have never heard of any problems. I have used Lucas trans fix in my tranny when the torque converter was chattering on lockup, and wouldnt lockup, fixed it immediatly. coulnt tell it was in the trans oil either, and its thicker than the oil stabilizer. I'd recommend Lucas products to anyone Just my $.02

[grancito]

Thanks JD countryboy, I'll do that, it will keep me mobile.

[torque454]

yea lucas is awesome. It works great at slowing down oil leaks too :) It has many uses.

[grancito]

Pulled it apart today, the push rods ends and rockers are worn bad on exhaust 5 and both exhaust and inlet 7 hence the blowing into the intake when the oil is hot, valves not opening properly.A friend is bringing 4 rockers, 8 retainers and 4 push rods at the end of the month, no parts here. The turbo came off easy and made working on it real simple. Thanks for all your help.

[grancito]

Remove rocker arm covers and rocker arms. Mark assemblies so they may be returned to original position during assembly procedure.
Remove guide clamps and guide plates.
Remove valve lifters through access hole in cylinder head using hydraulic lifter remover tool No. J-29834, or equivalent, and a magnet.
Reverse procedure to install, noting the following:
Some engines will have both standard and/or 0.010 inch oversize hydraulic lifters. The oversize lifter(s) will have a 10 etched on the side of the lifter. The block will be stamped O.S. on the cast pad adjacent to the lifter bore and on the top rail of the cylinder case above the lifter bore.
New hydraulic lifters must be primed before installation.
After guide plate clamp bolts are installed, turn the crankshaft manually 720 degrees (two complete revolutions) to ensure free movement of the lifters in the guide plates. If the engine will not turn by hand, one or more of the lifters may be binding in the guide plate.

Today I replaced the push rods and rockers on cylinders 6 and 8 (confusion on the cylinder positions in my original post) The problem is still there so conclude that the lifters are bad and hence wore the rods and rockers. I didn't find "OS" anywhere so assume standard size lifters, will order some. The tool to remove them, is it just a hook to fit into the oil hole?

[grancito]

Finished puting the 3 back lifters pasenger side today, couldn't get the 4th one out as there is a casting web that restricts the magnet, and figered it would be imposible to put the new one in. The other work was very difficult, lack of space and vision, 12 hours to complete. Has realy improved but still a slight pulse in the intake and altough the boost drops a little over 2500 rpm with some pressure fluctuation, there is no longer the vibration noise in the boost gage. Guess there is another bad lifter somewhere, it can wait, best remove the head next time.

[JD_countryboy]

Glad to hear your making progress, sucks it aint all together fixed though. Tarctor at work just came up with the same kinda pulse in the intake. No turbo. Its so loud that it sounds like a rod knockin :eek:. Needless to say, its in a dark corner till after plantin season. Its just a replaceable utility tractor luckly. Good luck with your teardown. Maybe you might wanna just yank it out, put some 18:1 in it, and soup it up a bit?

[grancito]

It will do for now, not bad, had enough of working on it, the Chev has been such a great truck, 16 years no problems, more miles than the suburban has. When I have a garage I'll rebuild the stupid engine completely. Seems like the later the model, the more inferior the vehicle.

[grancito]

This is a real old thread I started but the problem is now resolved. New rockers, push rods, lifters and 2 weak valve springs replaced. No pulse in the intake and no drop in boost at 2500 RPM. Prick of a job to change the lifters without removing the heads, about 20 hours work.

[chessie6.5]

That was a common problem in the old 5.7 diesels I used to work on. Mostly caused by worn rocker pivots, which was caused by worn lifters reducing oil going up to the rocker arms. If you take the snap ring out of the lifter and remove cap, you will find a small metal disc. This wobbles or rocks on rounded bottom of cap to meter oil up pushrods. This rounded bump wears off and disc sets almost flat, reducing or stopping oil up rod to rockers, causing the wear. This is caused by the soot in the oil, mostly on 4.3, 5.7 and 6.2, 6.5's diesels with operating EGR, especially if oil isn't changed often enough. These lifters are the same in both diesels, at least as far as that cap and disc. I think they are identical but not positive.

[JD_countryboy]

Glad to hear your up n runnin 100% again. Now you can drive it to your vacation destination. Or down to the cornmer store for more corona. lol.

[grancito]

I'm off to the USA towing a trailer on Monday to pick up my workshop tools, a box weighing a ton. Went to the city today for a wheel alignment after putting new suspension bushes, runs great. Will bring back lots of gin and tonic, can't get good stuff here.

[Garth J]

Too bad im still not in Az we could have met for a Rye and Ginger ale

[grancito]

Too bad im still not in Az we could have met for a Rye and Ginger ale

Perhaps next year you will make it down here.