Reviving a 270K mile Highlander Hybrid

[Piotrsko]

Aircraft (or is it late model big block dodges) look to see if the valve wobbles in the guide indicating off center wear or general oversize. I think 1/16" wobble was acceptable at the top, wee bit open, but there should be a spec for your engine somewhere.

[Drifter]

Oof, already 1 month in. At this rate, Xist might finish his shed before the HiHy is back on the road!

The heads are at the machine shop to get valve seats & valves touched up, along with resurfacing. ETA for this simple job is 2-3 weeks It would have been 4-6 weeks if I let them cut valve stems/swap shims to adjust the valve lash (so I still have that fun to look forward to doing myself when they come back). I was really hoping to have this ready for a 4th of July camping trip, but at this point everything would have to fall perfectly in place (and I'd have to do my part to hustle as well).

The good news is everything was in spec, although 1 valve stem was at the minimum thickness (.2154) according to my mic. I asked the machine shop to measure it with their mic and they came up with .2155. Seems pretty incredible to me to have 270,000 miles and still have every single valve stem and bushing in spec...

The head that had the clean combustion chamber, presumably from a blown head gasket, was warped less than I could measure (0.0015 is my smallest feeler gauge). The front head, which looked a lot nicer, actually was more warped at ~0.0015. I could not get the 0.002 feeler gauge under the machinist block so that's good (0.002 being the specified limit).

The valve guides/bushings, which I expected to be worn to the limit, were actually well within spec of a new guide and way inside the maximum acceptable oil clearance.



I'm currently struggling to pull the block without the transmission attached. There is 1 transmission to block bolt that I can't turn a wrench on nor can I get a straight shot on it with a socket. I donated some blood when this wobbly broke:


Once the block is out, I'll tear it down and inspect. I had assumed it would be worn enough to warrant a 0.5mm overbore, but maybe I'll get lucky and can get away with standard size rings on a fresh hone. I'd normally just bore it anyway, but parts in general are not easy to come by these days and this 3MZ-FE was used for a relatively short period of time in the US by Toyota standards (2004-2010) making unusual parts even tougher to come by. Well good quality parts like Mahle pistons or Clevite bearings (Toyota doesn't make oversize pistons). I can still find Chinese-made DNJ overhaul kits, but that would be a last resort...

That's kind of a shame - the 3MZ is really a good engine - much better than the 3.0L 1MZ it replaced (which itself was a good engine despite being infamous for sludging with extended oil change intervals). But Toyota introduced the even better 3.5L 2GR-FE in 2005 - just 1 year after the 3MZ - and by 2008 it replaced the 3mz in all but the Highlander hybrid (which would get an Atkinson-cycle version of the 2GR in 2010)

[Piotrsko]

I suggest wobbly extensions where the end is tapered, thinned, and lengthened so the socket can bend up to 15 degrees along with loose fitting drive ends on the socket. Harbor fright and couple of short cheapo black oxide air tool wobble extensions and sockets...minimum of 1/2" drive

Knurled pistons and perfect circle rings? Widen the compression groove and use 2rings?
(But not with a .5mm overbore [wait a minute my phone says thats .020" within the honeing range]) Sand blasting the outside of the piston skirt?

Back in the day kind of stuff for unobtainium parts mods.

[Drifter]

So the block has definitely been rebuilt in the past because as far as I know, Mahle does not make Toyota's pistons:



One of them shows scuffing on the skirt:


That cylinder bore doesn't *look* bad, in fact most still have pretty good cross hatching. But this other cylinder does not. I find it odd that the cross hatching is worn on the side of the cylinder rather than the normal wear from the crankshaft stroke:



The bearings all looked to be in like-new condition except the main bearings on #1:



Crank walk maybe? Bent crankshaft? I'll double check tomorrow, but I think the abnormally worn cylinder crosshatching is also cylinder #1...

[Drifter]

So I can't find 3MZ pistons in the current Mahle catalog, nor could I find them in a 2009 catalog (when the engine was still being put into new hybrid highlanders). So either Mahle briefly made 3mz pistons between 2010-2020 and discontinued them or they are the original supplier to Toyota (which would be a surprise to me since these vehicles were produced in Japan).

I'd greatly prefer this be an original engine rather than a rebuild that has already gone bad (after an original engine went bad prematurely).

Frequently Asked Questions

I have this part and it says MAHLE on it and I can’t find it in your catalog

We are sorry. Often customers have a bearing or bushing that says Clevite on the back or a piston marked MAHLE. In the majority of these cases, the part was manufactured only for the engine/equipment manufacturer and no aftermarket/service parts exist unless from that equipment manufacturer. The other possibility is that the engine you have is old enough that we have discontinued offering the parts, hence you cannot find a listing for it.

The piston with the most worn skirt measured 3.6201-3.6202 (factory spec is 3.6211-3.6216). That cylinder bore measured 3.6220 on the piston pin axis and 3.6224 on the piston skirt axis (factory spec new is 3.6220-3.6225 with maximum service limit of 3.6272).

Standard oil clearance is 0.0013-0.0023 with maximum service limit of 0.0051. So that worn, 1 thousandth undersized, piston in the sloppiest part of that cylinder has 0.0023 oil clearance which is barely within factory spec but still well inside the service limit. Honing would probably increase that clearance another 1-2 thousandths though which would put me on the edge of the max service limit...

I cleaned up the machined flat portions of the block and measured for warpage. All but one were as flat as I can measure. The one slightly warped surface was one side of the oil pan surface and it was just barely off (less than 1 thou). So nothing that would explain the odd main bearing wear on #1.

Cylinder #5 was the one with the most worn crosshatching, but #2 was the cylinder with the blown head gasket. Maybe when it was misfiring severely on start-up it caused the bearing wear? I don't know. I'll continue cleaning and Mic-ing the remaining cylinders and bores this weekend and plan to take the block to the machine shop on Monday. I'm cautiously optimistic they'll be able to reuse it, but unless all the other pistons/cylinders are worn less than the one I checked I'll probably be looking at an overbore with new pistons. Unfortunately unless I want to spend money on custom JE or similar pistons, I'd probably be stuck with China-made DNJ pistons. They're probably okay, but not to OE standards...


The only other weird thing I noticed were these irregularities on the webbing of the block by #5:


At first I thought the rod must have somehow come into contact with the block, but the rod itself looked fine. And how could that happen without the rod breaking or bending severely? So I'm guessing it was some void from the casting process? None of the other cylinder webs have anything like it.


Interesting is that it appears Toyota smoothed the casting on the inside of the block. It wasn't quite polished, but definitely smoother than natural casting. Seems like a lot of machinework for an OEM to do to (presumably) improve oil drainage slightly.

[cRiPpLe_rOoStEr]

It seems like the engine had been overhauled at least once. But what might've happened for it to need a previous overhaul?

[Drifter]

Yeah I kept trying to convince myself that maybe it really was the factory build, but the closer I look the more signs of a rebuild:

Stamped BBB - I don't see any local auto or machine shops by that name though?

My attempts to seach the internet are overwhelmed by links to the Better Business Bureau...


More aftermarket markings on the flywheel side of the block:



Disconcerting mark on the snout of the crankshaft. It almost looks like it was welded and reground?


It sort of seems like this sleeve is just below flush. This is the front cylinder that appeared to be blowing pressure into the coolant system (rather than allowing water to enter the chamber like the back blown head gasket cylinder):


The unknowns with this engine kicks my OCD into overdrive so I'm looking forward to outsourcing the final decision to the machine shop. I'll go over my concerns:

1. Why did the original engine fail and why did this rebuild fail?
2. Are the sleeves at the proper height?
3. Have the heads been resurfaced before &, if so, how much will compression & cam timing be affected?
4. Are we absolutely sure nothing is cracked? I've never seen a coolant system weep from every gasket at once
5. Why did one of the main bearings wear oddly?
6. Why did one of the cylinders wear oddly?
7. How long did the rebuild last? Most of the bearings & crosshatching look new, but it was full of varnish & carbon.

...And let the experts see if we can do a proper rebuild...

[Drifter]

As a plan B I'm trying to find what other used engines I can get since the number of wrecked 2006-2010 highlander hybrids & Lexus RX400h is pretty low and all locally have high miles. But the 3MZ was also used in the Camry, solara, es330, rx330, highlander, sienna - so if there is some minor difference maybe I can just reuse my oil pump or dipstick or whatever...


So far I can see that the longblock part number is the same for 2006-2011 Highlander Hybrids, 2006-2008 RX400h, and a handfull of 2006-2009 2WD Highlander non-hybrids.


Toyota has a separate part number for the longblock for earlier Highlanders, 3MZ Camrys, 3MZ Solaras, and the RX330.


The Shortblock has pretty much the same part number breakdowns - the highlander hybrid & RX400h have their own.

The Block sub-assembly, however, covers most of the 3MZs (mainly excludes not AWD Siennas).

Pistons use the same part numbers between hybrid and not, highlanders, camrys, solaras, siennas, etc.

Rods also use the same part numbers

crankshafts also use the same part numbers.

Bearings are the same

...The only different part number I can find is for the piston ring set - the highlander hybrid has a different set.

But when I look at the service specifications, the ring gap is identical between hybrid and not. The engine bore is identical. Piston to wall clearance is identical. But the piston diameter specs are actually different by about 1 thousandth:

3.6202 to 3.6207" for the highlander
vs
3.6211 to 3.6216" for the highlander hybrid


The Mahle pistons I have are measuring about 3.6205" so they were probably meant for non hybrid. But Toyota specifies the same part number for both??? 13101-20050


Long story short: All of this makes me think I may be able to use a 3MZ from a camry or sienna or something if the machine shop says my core can't be reused. But it makes me wonder why the hybrid would use different rings/pistons?

DNJ has different part numbers for hybrid vs non hybrid engine rebuild kits so presumably they felt it was important enough for a different SKU: https://www.enginepartstore.com/toyo...e-rebuild-kits

[nemo]

One of the more interesting threads I've seen in a while. That is sure an unusual location for piston scuff, is piston cracked or out of round? Thought on piston ring pt #s, the material or ring tension was changed trying for higher mileage.

[me and my metro]

That just looks like normal wear for the miles to me. The 6 #3s are probably factory bore sizes to match pistons when new. It might have got warm a few times causing bore wear. All the markings on the outside of the block look similar to what I have seen on Japanese engines over the years. If it is flat and round, get a pro power hone job and the correct rings and run it again.