I put a rebuilt head on my 4.0l inline 6cyl, and now there is no compression. Pulled valve cover all rockers are moving. Checked compression and 0. Pistons are moving up and down. I drove it into the garage. I know it is something I did, but what. This is my 100th head gasket I have done and never had this problem. Lets here what you got. I don't want to but I know in the end I am pulling the head again.
Whoops, I read it as a 4 cylinder. Try backing way off on all the rockers and turn it over by hand and see if you pick up compression then. Yes, sometimes you need shorter pushrods (I had that happen on a 302 Ford one time) but it still ran and had some compression. No compression in all 6 holes is very odd. Did you do anything else except a head job while it was down ? How did you check compression ? Don
Nothing done with cam or timing. I put a water pump on. I am leaning towards the pushrods being to long. Used a compression gauge. before I took it apart all cylinders had 135# to 150# compression.
If the rockers are on a shaft or with no adjustment fastening, then any cut off the head needs a shorter pushrod. How about a yr. & make on your 4.0 6?
If the pistons are moving up and down all that compression has to be going somewhere. Do you detect any compression out the carb or the exhaust pipe ? More I think about it, this has to be valve adjustment. Don
Ford 6 cylinders are sensitive to installed valve height and are affected by how much is surfaced off a cylinder head. Generally on a hydraulic cam and lifters your pushrod will plung approx. .080 into the lifter as a preload and work fine, BUT if the lifters ( when pushrods removed ) will allow the plunger to go to the top of the lifter bore. 2 options bleed lifters out and allow push rod to find its own height or mechanically force the push rod down to bleed a little oil out of the pushrod. Also, sometimes ( assuming spring pressure is good ) letting the engine sit static may bleed the lifter down to its operational preload. If that does not work you will be resetting preload depth via shorter push rods. some rockers are a bolt down non adjustable type and other ( even shaft rockers ) can be an adjustable type. If you need any questions answered, you can call me at H & H 1-818-248-2347 and ask for Max Sr.
Simple, as they said. Back off Rockers, and you will have Compression ! How many times has the head been decked ? and how much ?
Yeah, I get it. But don't you think that info will get you more quality answers. There's no adjustment on those. Lifters should be pumped up and rockers studs torqued to 21 ft lbs At TDC compression stroke & done. Did you do that ? ^^^ If so , back them off and do it again. If not, try doing it that way. If you still have zero- take the rockers loose and put air into the cylinders and track its escape route by listening.
Take the rockers off. Take out all plugs, check for compression. That will tell the story on pushrod problems.
No-Not really. The valves need to cycle, draw air in and compress it. With rockers off, and a compression tester you'd get a half assed reading that won't tell you anything. You try to draw a vacuum on the way down and back to zero on the way up with compression only being the amount past the starting point to TDC. The reading would depend on the starting position of the piston. If it were near BDC the reading would be much higer than if it were starting at TDC. This is exactly why I suggested putting air into the cylinders with the rockers loose/off.
as stated above lifter have jacked or are not compressing enough to allow the valves to seat.even had it happen to cars that had 10w instead of 5w in the winter lifters don't leak down fast enough you might try turning the motor 1/2 rotation 4 times letting it sit between shots or if you can loosen rockers or shaft
If rocker shaft type engine and you may sunk the valves into the head a bit more than the lifters car compensate. As an alternative, you can shim the rocker shaft stand higher. Might be an answer. Keep us posted as to what you do.
Ok not familiar with the engine, but I take it that the rockers are not adjustable from the discussion. Here is the deal, if you cannot adjust the rockers anything that you mill from the head will change the valve lash/preload by that amount. Hydraulic lifters are very forgiving and I would think that .010 would not harm you much but any more then that you should be having a problem and need to change pushrod length by the amount taken off the face of the head. For instance if you have milled the head .020 and you shorten the pushrods a like amount it will put you back to ground aero.
You did put the head gasket on, right? I know it's a dumb question, but you never know until you ask.
The rockers on the Jeep 4.0l engine are not adjustable. If the head or block was milled, then you have to shim the rocker back up, or use shorter pushrods.
Aside from one big pair of ports at one end, it is symmetrical. Even if you put it in backwards and upside down, it would still seal.
I think you have a valve timing problem. When coming up TDC intake should start to open. Then next TDC the exhaust should start to open.
Just as a test, you could throw 12 thin washers under the rocker fulcrums, and see if that makes a change. By no means accurate, but that would help isolate the issue, before you yank the damper and timing cover.
Many years ago I replaced the head gasket on my moms car that was a GM 2.5 4 cylinder,sent the head to the first machine shop for a valve job and clean up the head surface and it leaked coolant in other areas so back off and to the second machine shop where they surfaced it again. Went to start it and no compression so I backed off the rockers and got it running,had to put shims under the rocker arms to get it right.
Did a search for adjusting the valves on a Jeep Cherokee 4.0 and a ton of stuff came up on Jeep forums. I think that the guys are on the right track with the lifters not bleeding down to allow the valves to close all the way though. You haven't by chance been running a higher viscosity oil in it than Jeep suggests ?
before you had the valve job done, it had compression, now after the valve job it has no compression, PROOF if it ain't broke don't fix it.
Hi First thing I would do is take a air hope and blow air in all the spark plug hole and see if you can tell where the air is going. If out the intake and exhaust take off rocker arms and check again. If out the radiator cap then the head gasket is wrong. Toxic waste
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