Hi everyone, I have a 91 4runner V6 3vze. I found a guide on here to replacing the knock sensor, so I intend to do that this weekend since I have code 52 and performance is terrible. I've taken the off the plenum before and detached the many vacuum hoses so I have an idea of what I'm in for!

My question is on RTV and gaskets. It looks like I'll need to replace several gaskets (1 for air intake (plenum), 2 for the heads, 1 for water bypass, 1 for the egr). From what I've researched, I'll need to use RTV sealant on the plenum air intake gasket, but do I use it on the 2 gaskets on the heads? There seems to be differing opinions online so I just want confirmation. Also, sorry if this is a dumb question but, should I use RTV on the water bypass and egr gaskets as well?

Admittedly, I'm a novice and lack experience using RTV with gaskets. I've only replaced valve cover gaskets in the past, which did require it.

Thanks in advance for the help.

 

If you're using OEM gaskets you will want to follow the directions from the FSM. If you're using an OEM style gasket again follow the FSM. If I (important "I") was using a thin after market gasket I would probably use fipg of some sort, knowing that it means more work if I ever have to get back in there and the odds of reusing this gasket shoot to about 1/100. If I'm using a thicker cork style gasket I skin them with rtv/fipg on the bench and get something closer to what I expect a good gask to be.

It's always kind of a case by case basis. Heck even with a good " squishy thick gasket " you might wind up wanting some glue depending on how flat your surfaces are.

Always follow the book, if you can.

 

While code 52 can be hard to treat, it is almost never due to a bad knock sensor. It is more commonly due to a bad "pigtail," the wire from the sensor to a connector just above the lower intake manifold. Replacing the sensor, even if unnecessary, won't hurt (and if I'm wrong you don't want to have to go back in), just be sure you include a new pigtail while you're in there. (E.g., )

Pay attention to CO_94_PU. The FSM requires RTV on the valve cover gasket (for reasons which are obvious when you look at it). Not on the other gaskets you reference.

 

Good point. I have purchased a pigtail to replace that as well. Seems like a good idea to replace both after all the effort it takes.

Thanks for the info and feedback guys. Super helpful.

Related question that just came up -- anything else y'all recommend replacing while I'm doing this job? I was thinking the spark plugs might also be a good idea to replace since it will be easier access. Might also do a coolant flush, thermostat replacement, and coolant hose replacements as well. But I don't want to get too ahead of myself on what for me is a complicated job

 

Consider replacing the PCV valve rubber grommet (and heck, the valve too). Unless it's been replaced within the last three Presidential terms, I expect you'll find it has the consistency of concrete. On the 3VZE you need to have the plenum off to access it, so now's the time. The grommet is such a standard part your local parts store will have it. Be careful; you'll need to destroy the grommet to get it out, and you don't want a lot of pieces to fall into the valve cover (then, you'll have to remove that too, and once you do that, you should check the valve clearance, and once you do that ....)

 

This is the time to check/replace the small coolant lines running around under the intake plenum, and throttle body. They're probably as old as your truck. If they are, they might be getting to the failure point. Bulging, rotting away, getting soft and/or out out of shape (no longer in the correct shape, not weak and scrawny...), and so on. The barbs they go on may well be corroded to the failure point. Might want to check them as well. With it all apart, you have easy access to all this good stuff.
Of course, if you have to cut the hose to get it off the barbs, it will need replacement

Definately a good idea to at least check the spark plugs. Check their gap, if the ground lead is burned away, the center conductor worn down, all that good stuff. If they haven't been replaced in a few years, I, personally, would just go ahead and replace the plugs, wires, distributor cap and rotor, and so on. Use the Denso made plugs and wires. They are what the system is designed to use, and last a long time.

I just replaced all my hoses under the intake plenum, as I had one fail. Coolant all over the place. Big mess. All the hoses were original, and all of them were ready to fail. Also.
So of course, all the gaskets had to be replaced, and most of the vacuum lines were getting towords bad...
At least I flush/replace the coolant, the thermostat, and the 3 big hoses, every year, so I was able to save the coolant and re-use it.

Anywho, get ready. You may wind up replacing a lot more than you expect, BUT: it's a very good opportunity. Take advantage of it. Better now, than on the freeway miles from home!
Some of the small, preformed, hoses under the intake can get a bit pricey, as well. Just so you're aware.

Good luck to you!
Pat☺

 

Thanks 2ToyGuy. Some of my hoses are newer, others will likely need replacing. Like you said, it's a good opportunity to do maintenance work on the 3vze.

Having good coolant hoses seems important in a place like Yuma!

 

YEAH it was. Kinda important when 100° F is a cool evening. In the winter. I am SOOOOO glad I was finally able to move out of there. I hated Yuma for almost 30 years...

I just changed out all the little hoses under the TB and intake plenum last year. I am really glad they lasted as long as they did! I learned my lesson, though, and will keep more careful track on them from now on. I can't swear I'll be alive, and have my trucks, in another 30 years, but here's hoping!

Good luck with yours. Let us know how things go for ya.
Have fun!
Pat☺

 

UPDATE -- I've replaced the knock sensor, the PCV valve (which required removing the cylinder head cover, the grommet was completely solidified), spark plugs and wires, cap and rotor, thermostat, and some coolant lines.

However, while putting the idler pulley back on, a small bolt (belonging to the #4 timing belt cover) fell down into the timing belt area. Since the timing belt area is all covered, I'm very worried that I shouldn't try to start the vehicle while it's somewhere in there, since I imagine it could potentially wreak havoc. Worst case scenario breaking the timing belt or other parts if it gets caught in the teeth. I'm not sure how likely this is, but I'm not off-base with my concern here, right? Reckon this means I have to learn how to take off all the drive belts and timing belt covers to find it

 

Definitely don't start it with the bolt in there. Can you see the lost bolt? You might get lucky and be able to fish it out with a magnet.

 

I wish.. I tried for like 45 minutes to fish it out with a magnet with no luck. I'd say this is a good opportunity to change the timing belt but it's still in really good shape and has a lot more miles to go.

 

I wish.. I tried for like 45 minutes to fish it out with a magnet with no luck. I'd say this is a good opportunity to change the timing belt but it's still in really good shape and has a lot more miles to go.

 

One more question for when I'm fishing out this bolt (Apologies if this should be posted on another thread; I'm new so let me know if this is the case). When I put the idler pulley (the one at the very top, can't remember if it's 1 or 2), I think I got it on there correctly, but I'm slightly worried the belt might now be off by a tooth (there was some slack from the idler pulley being off, and the cams seemed to move a bit as well). I guess I'll know once I start the vehicle, and thankfully the 3.0 is non-interference. But do you think this is a possibility, or would it be unlikely to be able to get the idler pulley back on and mess up the timing?

 

Just remove the upper timing cover (so you can see the cam sprockets), turn the crank two turns and stop at TDC. Are the cam sprockets in the right place (marks pointing straight up)? You're good.

That's all there is to it.

 

Thank you sir!! I will definitely do that. It will be a relief to check before starting it up again. It's also such a relief to have a non-interference engine. I didn't learn this until recently. Praise the good Lord above.

Btw, you were spot-on regarding the PCV valve and grommet. The grommet had in fact solidified to the consistency of concrete. I was only able to get it out by taking a very small nail and bit by bit hammering into the sides to gently break it apart. Since I had the cover off, I could then shake out its remains. The area under the grommet inside the cover was very dirty as well, so I sprayed it and down and wiped it as best as I could with brake cleaner.

 

Did you check the valve clearances? Tsk, tsk. ;^)

Sounds like you're making real progress.

 

Re: making progress.. yes and no.. I took your advice and after looking at the timing belt.. I'll let the picture speak for itself. Don't ask me how I did this :



Again, I'm not sure how I managed to get the cams out of sync like that. But, hey another learning opportunity. LOL

So, I'm thinking there are a couple ways I can tackle this:
1. Loosen the tensioner, loosen the belt off the top portion, readjust one the cams with a wrench, put belt back on, then tighten tensioner back up and hope it gets back in sync, or
2. Take off the crankshaft pulley, timing belt cover #1, etc and start from the beginning by putting the belt back on. Also, adjusting the cams as needed and making sure everything lines up. Might as well use a new belt at this point, even if the one I have still has about 70K more miles to go.

Am I on the right track here? Like I said, I'm pretty novice, but I got time on my hands and feel pretty comfortable tackling this. I should definitely manually crank one of the cams to be in alignment right with the other, right? Any specific tips or advice for fixing this?

 

"There's yer problem, lady!"

Remember that you have to get three sprockets in sync, so you will (probably) need to adjust both cams. As you point out, the 3VZE is a non-interference engine so you can turn the cams once you've loosened the timing belt. (In an interference engine, you can feel the pistons pushing on valves, so you just let up and figure out what you did wrong. The problem is cranking it over with the powerful starter motor.) Because of the way the timing belt is retained on the crank sprocket, it's not easy to move the timing belt on that sprocket even when loose (which is exactly what you want). Again, it doesn't matter where the belt is on the sprockets, just that all three line up.

To remove the lower timing cover, you'll have to remove the crankshaft bolt (you know that). Absolutely doable, but a challenge. The spec tightening torque is 181 lb-ft, and you have to make a tool to keep the crankshaft from turning. But if you haven't retrieved that bolt yet, you're probably stuck with removing the lower cover. In which case, yeah, just replace the belt.

Others may disagree, but I think successfully replacing the timing belt is the task that separates the competent amateurs from the hacks. Are you up for it?

 

Hi:
I rebuilt my V6 engine about 9-10 yrs ago.
I was careless when reassembling it, and this picture is the result.
I have no idea how long this situation existed, but as long as I can remember, the engine always made a weird sound from 2000 RPM onward.
Look at this and be careful.
Art

 

I haven't retrieved that bolt yet, so I might as well remove that cover and change the belt. I'm up for it! I'll assume everything will go smoothly... lol

As far as getting off the crankshaft bolt, I've seen that you can use the trick with the starter to break the bolt with a breaker bar (and pull some fuse to prevent the engine from actually starting?). I'll look into this and other options. It sounds like getting it back on with proper torque may prove even more challenging.