Death of a 4.7l engine

Long story..

Bought 2006 DC 4.7l SR5 last Nov with 195,000km(122,000 miles). Have had a 2006 Tacoma Double cab 4l for 9 years but want to be able to tow more weight occasionally. Plan was to refurbish the truck to have a reliable 2nd vehicle for my hobbies mostly. I bought it from a young mechanic just finished school. It was in his family since new and he said he blew a head gasket towing too much trailer up a steep hill. Thinking the mechanic would have done a proper repair, I didn't think Id have to touch the engine. I just finished removing a terrible lift kit job and put it back stock: 4 ball joints, 2 tie rod ends, new front cv axle, new front cv boots, new brakes all around including rear pistons (fronts were seized and rears were way out of adjustment resulting in terrible lack of stopping power), several new brake lines, shocks on all corners, front wheel bearing and seal, front backing plate, rear axle bearing and both axle seals, freed up the parking brake, new windshield, repaired sticky climate control mechanism, removed faulty cheap led headlights, removed window tint, fixed brake controller. Started at the bottom; should have started at the top lol

The seller said there was a tick after the repair. It was faint and with a stethoscope I thought it was possibly fuel injector at back of bank 2. My buddy thought mechanical at back of bank 1. It was possibly intermittent? After 4000km, I got a code that bank 1 was stuck on rich.


First road trip, 2 weeks ago I drove about 1100miles towing 2000lbs. I took it easy and didnt let it go over 3000rpm. It was running smooth at about 2100rpm with cruise on holding 60mph. The vehicle just died with no warning. 100% electrically dead. No sound, no vibration; just quit. Fiddled with the positive cable and got power. Tried starting and it made bad noise like compression going out the intake so towed it home. Pulled timing cover expecting broken belt. Nope, intact and tensioned. Hit starter again and it locked up.

Just got the heads off. Valves in #6 and the piston top are trashed. A valve seat rattled around inside #5. There's a chunk of possibly broken valve stem stuck in the head on #8 that hit the piston. The fuel injector on #6 was leaking on the outside. The intake manifold at #6 is 30% clogged with carbon buildup.

I assume both heads are trashed. The cylinders are untouched. Anyone have any idea on the sequence of events? Even if a seat dropped or a valve head snapped, how does it get out of timing on the other cylinders? How did this much damage happen with no noise?

 

OUCH, that one hurt.. i've had a headgasket repair another shop did that also did valve stem seals drop a valve. only guess was they didnt fully seat a keeper.

are the cylinder walls damaged?

 

I'd be leaving the heads on that guy's doorstep with a note, "You may want to choose a different career, dickhead!"

(I mean, it'd be cooler to leave the whole block with mangled piston heads installed, but ... since the heads are off already ...)

 

Was the timing belt recently replaced? Is it possible the belt broke on the previous owner and the repair he described was a cover up for that fact? He haphazardly did a valve job to attempt to repair the damage done by the snapped belt hoping it would hold long enough to sell to the next guy?

 

I agree with Dan, valve keeper wasn't seated correctly, that's a real shame buddy.

 

It looks like the head had valve seats and possibly guides replaced, due to snapped t-belt. It wasn't done properly or couldn't be done properly due to the damage it received during the belt accident. Anyways, I wouldn't have any trust in the block as well, not until fully disassembled, inspected and measured. At which point it is cheaper and quicker to replace the engine with a good used one.

We all wish to that dickhead a personal liability case in his dickhead career, so the dickhead would learn that being a dickhead is not tolerated in our society the hard way.

 

Valve keepers are all in place. Stems are all in place. 2 valve heads inside chamber on 6. Pulled half a seat out of intake on 5. Cant find the other half yet. The cylinder walls seem untouched.

 

It's in the cat. Probably can find it with inspection camera via front H2OS sensor hole.

 

Sorry to see it happen. Thank you for sharing photos, very educational(to me) both photos and replies. Sadly this happens in all trades and the culprit will likely enjoy years of carefree work. Good luck with sale.

 

Took heads and cams to machine shop. The owner is awesome and discussed everything with me. One head is repairable. I discovered that some cam caps had been installed in the wrong places and there is a tiny bit of odd wear on one set of cams. I'm looking for the right side head casting. $1650 from Toyota.

I'm pulling the block today and I will do the teardown. If the measurements prove that there is very little wear on cylinders and a flat deck and good crank and good rods, I will have them do a hone, clean, and I will install new bearings, seals, pistons, rings. They will polish/grind the four cams and install 32 new valves and seals with fresh grind/lapping.

Its $4000 for a used engine with 35000 more miles on it than this has. I'm going all in and have a known excellent engine and peace of mind for a few dollars more. After 6 months of driving, Ill be ahead money wise from the option of junking the truck and buying a newer one.

 

Awesome! Please keep us posted. This is hugely interesting to me and I know a couple of others on here.