Chris thanks for the continuing education on the function and care of the various sensors that give us trouble. I'm slowly gaining a good understanding of modes of failure and the symptoms. Chris, lemme pick your brain for a minute. As I've mentioned before my 4L pushrod engine makes a big heavy metal internal rattle at revs around 2800-3000 rpm. First I thought timing chain but it wasn't. Then I thought valve train, but now that I've removed the heads from another 4L engine I doubt it, the noise is dramatic and I think if I had something wrong with a head I would see more symptoms. Now I'm thinking maybe a rod bearing, yet the engine makes no bad noises at moderate rpms and power. I know it's only conjecture to try to diagnose a noise without hearing it, but do you have any experience with valve train or bearing failure and what they sound like? I've only checked with one local machine shop so far about rebuilding the motor, but they want $1600 for the rebuild kit and another $800 for the machine work and assembly. Is this the best way to go? Are there cheaper places for the rebuild kit? I'm hesitant to use a Kragen re-man. thanks, Michael

Michael, It is rare that any rattle will require a rebuild. You can first do a pressure test on the cylinder. There are several different ways. Remove a plug and using a pressure gauge. (the zone has one for $30.00 or so), it should get up to 90-100+ pounds. If not it could still be bad valve seats. You can check the rest of this by moving the timing mark to TDC (top dead center and find #1 cylinder. Using the hose from the pressure gauge, connect an air line to the cylinder. You can hear a hissing in either the intake, exhaust, or worse case from the hose that runs from the valve cover to the intake. This is blow-by, meaning you have leaking rings or leaking valve seals.   I would guestimate 50% of the time people have their engines rebuilt, they only need a valve job. Remove the heads and take them to a machine shop if you don't know how. You can remove the heads yourself, if you wish. One little hint there though. Don't ever use any RTV (red, blue or otherwise) on any part of the engine near a oil vein. This can clog up your oil veins.   I didn't catch now many miles you had on this vehicle. A common problem at about 150K+ is not a bad timing chain, but a stretched one. This can only be noticed by a timing light and some engine pressure, which is hard to do parked. The slack comes out under pressure sometimes.   A heavy metallic problem sound a lot like a push rod. Push rods make a lot of noise at times when they aren't the problem. If you have enough miles you might want to opt for the head job, and request all new seals and springs.   A "tap" sound is often from a bad valve spring not keeping the rocker against the pushrod. I have a SOHC now which won't do that.   There a few trouble shooting options here. *Take of the blow by hose (the one from the valve cover) and see if there is any fumes or much air coming from it. Spun bearings have some of those symptoms. *Oil pressure, I'm sure you have a gauge for that, but sometimes a vein can get clogged and you can still have good oil pressure.   Is the noise coming from the bottom of the engine or the top? When it is running place your hand on the oil pan and then the valve covers. Try to determine which side it is coming from.   There is a million and one things, but top or bottom isolation helps a lot. Also which side helps. Check the oil pressure, etc.   If the vehicle has a lot of miles, it may very well be the main bearings. (this is a reach) they are o

The 4l has shitty crank and Ford has known about it for some time. I rooled a rod bearing on my 91 at 100000miles, i asked around and was told the guys selling the wreck motors would roll them over and always change the crank and bearings put on the pan and out the door they go. I bought a ford rebuild with th 30000 and 3 yr warrenty. Its knoking again after 20000miles.and less than one yr. 4.0 is crap

no Your 4.0 is crap. I know guys with 280,000+ that still don't even use oil. Mine only has 190,000 and has no knocking and no oil use..at all! Sorry you got a bad one, but that is like saying all white folks are bad because we have 10 fools.       Chris Robertson

Mine is 10 years old w/122k miles, no engine knocks or any oil issues........ a good maintanence schedule pays off.   Kerry T  

Chris

Phew, thanks, Chris - was getting concerned. George   On Tue, 13 Jan 2004 08:36:54 -0600 Chris Robertson <

ditto '95 130K, 4X4, change oil every 3-5k miles and tranny is flushed every 30k! Running strong >