my4runner

How difficult is it to change the pistons? Are there any diagrams on how to do this procedure? Any help would be appreciated....thanks

liferunner2

Why do you want to change your pistons? Changing the pistons themselves is not that difficult, it's getting to them that is the problem. You realize this will basically end up being a full engine rebuild.

Chris

MMA_Alex

yeah basically pull the oil pan. remove the connecting rod cap, and pull the piston out.

To put em back in you put a ring compressor around em, and slide em in from the top, and reconnect the connecting rod back to the crankshaft...

and yes thats extremely simplified.

As stated above its like 2 steps from doing a full rebuild, and if you're gunna take it down that far you might as well go all the way... Unless its a diesel and you're changing the powerpack (piston/rings/cyl liner combo)

theres not really a reason to change the pistons though unless you're boring out the cyls, or you put a valve through a piston. what is the problem?

my4runner

I was told that one of my pistons is slapping when I de-celerate...can I change the pistons with the motor still in the truck, or will I have to take it out? It has a brand new Head!!! Will I need to bore it or just hone it? Thanks guys!!

Jeenyus04

you can just hone it but when you have it down that far i'd do a full rebuild atleast on the bottom end if you say the head is new

TNRabbit

Be certain that's the problem before you go to this much trouble...can you describe the sounds you're hearing? Is it there at startup? Worse or indifferent during acceleration? Remove the plug wire from each of the cylinders in turn as the engine is idling & listen for the sound to lessen or stop altogether...report back!

my4runner

The sound sounds like a rod banging, it happens when I let up on the accelerator...when I give it gas, it doesnt make the noise, also, when I am driving at a constant speed, any speed, it starts to knock.....I am sure its not the timing chain, its new as well, and that has a different sound when going bad........TY

dcg9381

Short of some amazing hands, I don't think you can get them out from the bottom with the motor in the truck. They won't clear the crank.

You have to pull the head, then pull the pan. Pistons come out from the top.

If you've got piston slap - true piston slap, it's very likely that you need machine work...

Basically, if you're in there replacing bearings / pistons / internals - you'll want to do it right which requires machine work. Otherwise expect to be doing it again shortly.

surf4runner

if you have to ask, im guessing its not a job for you.


sounds like whoever just did the top end has some more work to do (from something they did wrong perhaps)

just a 22re

ok piston slap thats when the pistons get very very pissed and start slaping the cly walls trust me thats a fight i dont wanna be in now you said you have a knock at start and when your costing and slowing down aye? wow sounds like about 3 months ago for me...... PULL THE MOTOR!!!! trust me buddy its not piston slap that a rod bearing and yes it will spin on you trust me and if that happens you need to do a full replace not a rebuild trust me thats what i had to do crank cause the spon bearing cracked the crank new rods rings hone cam 5 angle head job valves springs timing chain everything thats just cause it was all out and i wanted to though but the pistons as mine were just fine but now i got a slight piston slap when shes cold but other then that shes a dream so yeah pull her before she locks up on you buddy!!!!

my4runner

Thanks everyone for the help, as for this not being a job for me, well, theres no better time to learn now, and from the (possitive answers I got on this post) I should be able to do the job....the reason it has a new head, the old one was really rotting out, so (I) replaced it...the block has never been worked on, it has 320000 miles on it, if I dont ask questions, nothing will be done.....so again, thanks to all of you for the help

MMA_Alex

If you're gunna do it rebuilt it all the way at that mileage. Some searching will find a ton of info on how to do a rebuild. Take your time and do it right, and make sure everything is in spec, and you'll end up with a reliable engine.

isaac338

if your pistons are slapping loud enough that you can hear it, your cylinders are likely worn out of spec (especially with that mileage!). meaning if you replace the pistons with the same size, your cylinder will still be worn out of spec, and you won't fix the problem.

pull the engine and have the block machined - if you're going to do it, do it right, or don't do it at all. it'll save you tons of money and headaches down the road, believe me.

my4runner

I have taken your advice, I will install a new block, I plan on keeping my 4runner for some time.....thanks again

surf4runner

^do it right and youll easily get another 300K out of it!

remember: there is never enough time to do it right the first time, but there is always enough time to do it over.

my4runner

Thank you!!