Greetings,

I have a 91 2nd gen 4runner 3VZ manual 4x4. I recently did my timing belt, water pump, thermostat and hoses, and after the fix noticed i was losing some coolant. I thought I may have had some air in the system so I went ahead and burped the system several times to clear it out, only to realize that I am leaking coolant out the HG on the driver and passenger rear side (coolant coming out from between head and block and dripping off of bellhousing, worse on drivers than passengers. At this point, with over 200k on the ticker (and a new clutch being necessary) I think it is time to pull the motor and freshen it up. I plan to pull the motor, strip it down, and take it to the machine shop to have all work done get ready for re-install. However my main question is, with all of these "master rebuild kits" out there, is it absolutely necessary to install new pistons? If the machine shop doesnt have to bore cylinder am I just fine installing the original piston into the motor? The plan so far is to use DNJ components and gaskets from rock auto along with a set of LC (ARP) head studs with MLS head gasket and new AISIN oil pump. Ultimately Id plan to add a marlin crawler clutch with the install and new vac lines and sensors (the hard ones to get to under the plenum) and injectors and call it a day. Does this seem like a logical plan? Im in the process now of budgeting the whole operation and just want to make sure that reusing the stock pistons is an "acceptable" was of rebuilding a motor...

Thanks,
Dylan

 

Depends on how much piston and cylinder bore wear there is.
The machine shop will take measurements.

 

There is no issue running a used piston assuming it still fits the cylinder and has no damage. . If there is excessive wear/taper ect making it nessacary to bore to a larger size new pistons would be required.

 

Awesome! thanks for the replies. I suppose I will plan on keeping a set of pistons as a potential cost. I certainly wont plan on buying parts until I hear about it from the machine shop. Now onto the big project, hopefully pulling a motor this weekend!

Thanks again gents!

 

original pistons are actually better than most aftermarket parts even with 200,000 on them . unless damaged . use oem seals , nothing is worse then buttoning up a great running engine then noticing the rear main spewing .

 

200,000 miles it is not the pistons you need to worry about it is the block that will make or break you.

If your luck is very better then mine you will get away with out boring.

Me it seems one cylinder is always worn hard enough.

 

I'm certainly hoping for the best. I don't think it will end up costing too much more if I do end up having to go with bigger pistons. From what I've read people seem to have good things to say about ITM rebuild components, at least that what I was hoping to go with (can't really afford OEM, nor do I think I would be willing to go that route on a vehicle worth less than 2 grand) thoughts?

 

Only you know what you want to spend. Or can spend.

Then again I have spent several thousand on a vehicle worth the price for scrap.

It comes down to what it is worth to you!!

 

Okay, certainly a valid point on it being what it is worth to you. I am still heavily researching and will definitely look at all npr hardware, which is I believe what toyota used from factory for internals.

 

After some more deliberation and research, Wyoming9 was definitely right. If I am going to go to the expense to switch to head studs and MLS head gasket, I may as well make sure I'm buying quality components everywhere else. After looking around, I see that I can get my hands on NPR rings and king bearings (the same stuff engnbldr uses) for not much more coin, so I am going to go ahead and do that. But, one more question, any recommendation on quality gaskets? I know the MLS is best for the head and thats what I plan to run, but for everything else is something like FEL-PRO going to be best? or is there a particular gasket maker I should source from? Thanks!

 

Back in the dark ages before the internet. Might be hard to believe but Silicone was not even used yet.

I would go with whatever gaskets happened to be sold where i bought the engine goodies..

What is nice when I screwed one up and I did a few I could go down the street and buy the same one rather then point and click and watch for the brown truck.

You all ready know your Head gaskets are the critical ones.

 

Thanks again, sir! I would have never thought about laying out the extra cash for the studs and steel gasket until I read here that it pretty much solves that cylinder 6 leaking issue. Seems like easy insurance. I think I will go with a set of evergreen gaskets (used a set of their valve cover gaskets when I did the timing belt, they seemed decent) off of the brown truck, and if I need any more here in town I'm sure I can find some local substitutes. I suppose it's time to get crackin' then! Hopefully I will have borrowed a friend's hoist and cleaned out the garage by the time the weekend is up! Thanks again.

 

Okay. So I may have just had an epiphany. I was sitting here talking to my buddy, and he said "are you sure it's the head gasket?" And it got me thinking... And I did run the heater that night, and the center console heater did work... And the main heater did NOT. So perhaps I will start by looking at my heater hoses. I'm really hoping the one out of the tee into the cab is what's bad, which definitely sea possible, especially since I noticed oil and water have not mixed.... I will update as soon as I know!

 

Pressure test the cooling system it should make it easier to find the leak.

With the pressure in the system it will force the cold coolant out at the point of leak.

 

Going off of Wyoming9's advice , but not necessarily all the way. I went ahead and topped off coolant and drove the vehicle for awhile. Up and down the freeway, a solid 30 mile commute at 75+, normal operating temp, no white smoke. I got the vehicle home, and sure enough, not as much of a stream of coolant, but dripping around bell housing area. I went ahead and looked at both sides of the head, pass side bone dry, drivers side a little oily (valve cover slow leak) but nothing crazy. I can see residual pink crud on the back of the motor from dried coolant (noticeably higher up on the firewall than the heads), but I know at this point there is pressure in the system. I went ahead an wiggled all of the heater hoses behind the motor just to make sure one of them wasn't bad. As I went wiggled the hose that goes to the tee for the front an aux coolers, a pressurized stream of coolant started shooting straight back onto the firewall where it would drip down onto the exhaust manifolds. I THINK/HOPE that I have found my leak source. I am going to head and change all of the coolant hoses on the back of the motor and report back. Hopefully the dripping/ loss of the worlds most expensive pink coolant comes to an end soon!

 

Hoses are much cheaper then doing a engine.

Just be glad that hot coolant did not go spraying into your face.

I much rather get cold coolant sprayed on me then hot any time.

 

Threw new hoses in and fixed a slave cylinder issue, and she doesn't leak a drop! Crisis averted. Thanks!