A little while ago, I made a post asking if anyone else had experienced leaking freeze plugs in the back of the cylinder block. Well, my 99 4Runner had that, and while the shop was doing that job, something happened and they damaged the driver's side rear cylinder, necessitating repair/machine work to the block and a rebuild of the engine. All on their dime, thankfully...

I'm not even quite sure how this happened, still need to ask them more details. This is a specialty Toyota shop that I've been using for years, so I trust them, but still want to make sure things are done properly. The truck only has 135k on it.

Anyone have advice they want to offer on what you'd replace while in there? My list so far...

1. Knock sensors and harnesses
2. Oil cooler coolant lines
3. Rebuilt injectors (maybe overkill)
4. Engine/transmission mounts
5. Oil pump (Aisin)
6. Every vacuum line I can lay my hands on

Some other general questions...

1. The cylinder heads should be resurfaced prior to mating, right?
2. I'm reading Toyota switched from composite to MLS head gaskets. Should I push for MLS head gaskets?
3. I have no idea if the cylinders should be reused or not? With new rings and other wear items, of course.

I'm way out of my element here, although I have watched Timmy's head gasket video, which is helping point me at least towards things to watch out for. Would love any advice others offer!

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WTF?! 135,000 miles is barely broken in. What did they do to it? It shouldn't need anything except maybe a little valve work and have the heads resurfaced. These engines go a reliable 250-500,000 miles. I don't understand what happened.

All the information I've got is that they damaged the inside of the block somehow getting that freeze plug out, which was extremely corroded from the coolant leak... I got thrown all the info this Friday and sort of was too busy processing to ask intelligent questions. The block apparently can be saved by the machine shop.

They did say that the oil control rings on the pistons were pretty clogged, which is a bit surprising for such low mileage.

I don't think knock sensors necessarily need to be replaced. At 135K, they haven't seen a ton of heat cycles. Maybe the pigtail harness though. Engine mounts are a nice to have sort of thing but they are very spendy!

Sounds like the either tore up the threads or applied so much force the block cracked. I sure hope they can repair it.

Taking out a freeze plug cannot damage the inside of the cylinder wall. Something isn't right here. This sounds like when my friend had his boat winterized by a guy from South Carolina who bought the local boat guys place and obviously didn't know how to winterize boats for New England winters. The manifold cracked and the dude tried to say it was already like that. He told a bullshit story which was obvious to me. You don't have to rebuild an entire engine because of a rusted out freeze plug.

Yeah, I was surprised to see they're $130 each, and I refuse to use non-OEM for critical parts like that. I'll get a look at the original engine mounts and see how they look. I recall Timmy's being not in too bad of shape in his replacement video.

These 5VZs don't have sleeves, do they? If they hit it hard enough to damage the internals, I have no idea how they'd repair it. I was just relieved to hear that I wasn't getting some crusty junkyard engine block going into this otherwise southern rust free truck.

Here is what was pointed out to me - there was so little space between the freeze plug and the cylinder. Something clearly happened, because they're fronting the whole bill. I'll for sure ask more.

There also is the fact that the whole engine was already torn down by the time I even heard about the issue. I've used this shop for nearly 10 years now and trust them, but as I read my story back to myself, I'm also wondering how this could happen...

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This has happened before, the rear freeze plugs sit right against the cylinder wall
and if you try drill it to put a screw in it you can drill right thru the cylinder wall.
If you try to use a hammer and screwdriver, you can break a chunk out of the
cylinder wall. I know people who have done this replace the block or engine.
I would like to know how the machine shop is going to repair this mistake,
either with a sleeve or weld. Either way it is a nightmare. I would want a
replacement block.

So what's the proper way to remove and replace these freeze plugs?

OP. Sorry to hear about this as that's a major bummer.

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This is becoming my main concern... I really want to know what happened to the block and the details on how it can be saved.

I didn't pay a small amount for this truck, and given the low mileage, I really want to make sure things come out for the better after this ordeal...

Talked to the shop this morning and got a few more details.

As I suspected, when they were removing the freeze plug, they chipped the cylinder wall. The plan is to repair the block using nickel rod, and then sleeve that piston so they can get the proper fit for the OEM pistons.

When asked why not replace the block, they told me that Toyota has tight (select fit may be the term?) tolerances between the OEM internals and the block, and they'd much rather save the block versus throw them into another used block, or use aftermarket internals.

They assured me that this fix will leave things only for the better, and I guess at a certain point, you have to trust the shop doing the work... I've never had a reason to double guess their work until now after nearly 10 years of them working on my Toyotas.

At least they are fixing it with oem parts. So they not only chipped the block but drilled through the cylinder sleeve. Man what a project for changing out freeze plugs.

They don't want to get new short block because of the cost as well as I am not sure they still available via Toyota

Plus you don't want aftermarket junk inside your engine. I made that mistake in a 1983 22r. The timing chain tensioner failed ground the case off ND dumped antifreeze into my crank case.

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