We put our 99 explorer 4.0 v6 in the shop two days ago to have front timing replaced. They told us this morning they were putting it all back together and it should be ready today.after no word from them we called and were told only that there is something wrong and they are not sure what yet. A relative of ours is a lube tech at the shop and says he’s not sure what’s going on except it has no compression in the passenger side cylinders and it won’t start and that they are now pulling the whole engine. Husband suspects they incorrectly installed front timing and caused back timing to jump, or maybe some worse damage.Can anyone offer suggestions as to what’s going on, to ease my mind!?
The valves are out of time.
How can that happen if they only were to replace front? In most worried because I’m already over budget AND original estimate.has the mechanic made a mistake that could cause this?
There is no front vs rear timing. When they lined up the timing marks they probably did not turn the engine over by hand enough to see if the timing marks still were aligned…verifying that the timing was correct.
Why they are pulling the entire engine is beyond me though.
Yosemite
I think one version of the 4.0 uses 4 chains and a handful of tensioners. To access the rear chain the engine has to come out so obviously they suspect something gone wrong in there. Pretty sure this is an interference fit engine so any timing out of whack could lead to upper end damage.
Just curious, but how many miles on this vehicle?
Car driven to the shop or towed?
What were the reasons for wanting the chain replaced? Noise?
I stand corrected. I didn’t know it had a rear chain.
Yosemite
ok4450 is right, this must be the OHC engine. The front of the engine has a chain that runs the left camshaft and a jackshaft that runs to the rear of the engine, where there is another chain set that runs the right camshaft. Due to firewall clearance the engine needs to be removed to service the right side timing set.
But if the original work was limited to the front chain set, any misalignment done there should be able to be corrected there. I wouldn’t be pulling the engine just yet.
What was the problem with the front timing set? Noisy I assume?
It has 121,000 miles on it.only two previous owners and has been beautifully maintained.timing guide was bad, took it in to fix the noise.found out today what happened. They did not hand crank it first…started it up, it jumped time, and now the shop is paying to replace the head, cylinders and possibly piston.They claim the new timing guide was faulty but we very strongly suspect it was human error.I don’t care as long as I’m not footing the bill for the mistake. This is my first real experience with having a shop do a major repair,my husband usually has friends or family to help. I’m extremely disappointed. And a little mad, I’m out a vehicle assist two weeks for a 10 hour job.
It sounds like there is going to be more $ spent on this vehicle than it’s worth.
Sorry to hear you’ve had this experience. While it would be a rare thing, a failed replacement part could indeed cause that to happen. It’s good the shop is taking responsibility and not trying to lay the blame on you. And you will end up with a lot of new parts in a 16 year old engine, so there is some upside for you.
The odds of a new chain guide being bad are zero in my opinion and I also strongly suspect human error was the cause of this.
This kind of thing has happened many times when DIYers or mechanics in a shop have replaced a timing belt on an interference engine and blindly hit the key without rotating the engine through by hand and double checking their work first.
The split second of chatter when the starter motor engages means the damage is done… 
I just looked up pictures of your engine…and the guys are correct. You have the Overhead Cam 4.0 in your truck. If they went about changing just the front timing chain…they had a prime opportunity to get things out of “Time” in a hurry. The front chain does indeed drive a Jackshaft that goes to the back of the engine… HOWEVER…if they did the primary work on the front of the engine…they had a DIRECT Opportunity to get the engine out of Valve Time… The Rear gear which drives the passenger side of the engine would not have been affected EXCEPT for Primary time. The ONLY WAY they could damage the drivers or “Left” side cylinder head and valves is when they did the front chain… that front chain drives the Jackshaft that runs through the block to then drive the cam on the other side of the engine. The technician needs to be INTIMATELY FAMILIAR with what he is doing…this is NO JOB for the novice. For reasons you are experiencing right now.
When they did the front chain…for what reason I have no idea…they got the drivers side Camshaft out of Phase. This is the reason the drivers side cylinder head or valves got damaged and or bent. What happened was the tech had the motor at TDC (Top Dead Center) and did NOT properly secure the left side cam… They tend to want to move one way or the other at TDC because of reasons I wont go into… But what happened was they didnt secure the cam and it turned a few degrees and got out of phase… then they attached the new chain with the left side out of phase… THEN MISTAKE #2 was the tech DID NOT rotate the engine BY HAND with the motor still partially disassembled…to DOUBLE check for proper cam phase and for any other issues such as binding… IF HE HAD TAKEN THE TIME TO HAND ROTATE the crank…this issue would never have occured… ANY tech would have FELT the engine BIND at a certain point and IMMEDIATELY would have known they were out of Phase. The other side of the engine would be fine since the connection to that cam was not changed …the only change could have been the Primary timing for the Jackshaft… This is why all the damage occured on the drivers side.
This was HUMAN ERROR…on a job that is not the hardest but one that still to this day screws less experienced techs This is serious Stuff people… It only takes you a few moments to run the engine thru BY HAND to detect possible problems such as this. You would have found the issue while using your hand power…STOPPED…Backed Up…and simply gone about the proper Cam Phasing like you tried to do in the first place. I cant tell you how many engines I would have done this exact same thing to HAD I NOT simply rotated BY HAND… SIMPLE PROCEDURE…>SIMPLE FIX… This step has saved my Arse more than many times…THATS WHY WE DO IT!!! To this day I STILL DO THIS STEP…Even with all my experience…and knowing that I got everything Perfect… I STILL DO IT… Im not above making mistakes still…so I will always do this. THIS WASNT EVEN A DIFFICULT ENGINE TO WORK ON…YOU WANT DIFFICULT??? Try doing a similar service on an engine WITH 4 CAMS and TWO CHAINS or Belts!!! THATS WHEN THINGS REALLY GET FUN… There is NO ROOM FOR ERROR HERE…It is either done right…or its OUT OF PHASE… OUT OF PHASE…NO PROBLEM…You will find out when you rotate the engine BY HAND…then go back and correct the issue… If you simply turn the key being infinitely confident in your work…the damage will be done FAR FASTER than you can shut the engine down…ITS TOAST AS SOON AS IT FIRES UP IN THE FIRST FEW MILLISECONDS…QUITE LITERALLY
They are pulling the engine…NOT to address the rear cam …but to be able to pull the left cylinder head for replacement…
Tsk Tsk Tsk…shame on that tech NOT Rotating BY HAND…This all would have been avoided. I’d HATE to be that guy right now. The shop will be eating a lot of money and time. Someone might even lose their job. Sucks for ALL INVOLVED REALLY.
Blackbird
The instructions in the factory service manual for my Corolla say to rotate the crankshaft by hand 4 rotations after changing the timing belt and then double checking all the timing marks still line up. Only after that test passes are you instructed to replace everything and start the engine.
Yup…I think we can all agree on what the “Tech” did wrong. Now what are they gonna do about it? Its almost easier to swap out the engine with a known working example…LOL
Blackbird
“known working example”
Hopefully a used engine that isn’t overdue for a timing chain and/or guides
They are supposed to have the head back by mid week…I’m praying they can get it back together this time without screwing something up again.I cringe to think what further damage they could cause. Hoping for safe return to me by next weekend.only two weeks for a ten hour quoted job!! 
@jfp Here’s a thought . . .
It might be a good idea if the guy who worked on your truck the first time does NOT work on it again
I’d suggest you politely request the shop foreman/lead mechanic to either do the work himself, or at least double check the work, before anything goes wrong