2006 4.0 Head Gasket Replacement Journey

Greetings folks!

I'm gearing up to replace the head gasket on my 06 Tacoma with around 300K miles on the original 4.0L, and have been reviewing related threads here and finding loads of helpful information. I'll be starting the job in ABQ, NM in about 2 months, so I want to get started now on ordering parts and preparing for doing the job myself (with another buddy). The threads I reviewed are a few years old, so I don't know if the resources/users referenced are still usable/best available.

Mostly reviewed: https://www.tacomaworld.com/threads/2006-4-0-v6-head-gasket-overheating-rebuild.609265/

Original symptoms similar to those mentioned in this post, (overheating/overflowing, replaced every component in the cooling system (twice), currently have exhaust bubbles coming up in the radiator). Checked compression about a year ago and everything was fine, and camera showed that everything inside looked clean, but that was over a year ago. Been using "high mileage full synthetic 5W-30" for the past few years, change it out every 5K. Recently had the coolant flushed, and everything else regarding how it runs seems fine.
Likely replacing the timing chain and tensioners while I'm in there, since I'm at 300K miles, potentially cam gears if it's worth it. I'm open to suggestions, as this is my first time diving this deeply into the motor of the truck I've had for over a decade (and driven from the Arctic Circle in AK all the way to Guatemala). Don't want to part with it, and would rather not swap the motor (unless I find a deal on a good low-mileage one, or if I find more problems after opening up the OG engine).
I've got a Sun-Lite pop-up camper in the bed, which I've been living in/working out of since the pandemic. Can't go anywhere until this is resolved, and anxious to get back on the road. Currently working in AK to save up the dinero for this job, and other overdue facelift projects for the truck and camper. Project will begin when I return to NM in October, and if all goes well I hope to be back on the road in February all spiffed up for around $5k total.

So this is my preliminary post, I welcome any resources for purchasing the parts that I'll need for the task, and will keep this thread updated with info and photos once the project has begun. I'm sure it'll be a challenge, but I've got the time, shop space, and the desire to learn how it's done.

Thanks in advance for tuning in and providing any feedback that you feel may help my process along.

 

Timing question:

I’ve got the motor opened up and see that the timing appears to not have been set correctly by the factory. The marks on the chain are 6 gear teeth off from the timing marks.
I’ve marked where the cams and gears are, upon reassembly do I put the chain back where it’s supposed to be or where the factory put it?
Additionally, I will be installing the new and improved exhaust cam gears.
Thanks for any input.

 

From what I understand, the painted chain links don't necessarily have to line up with the timing marks on cam gears when setting the timing. Someone correct me if I'm wrong.

See this link: Cam gears for V6. Add power AND mpg | Tacoma World.

 

I’ve since learned the same. If I kept spinning it around and around they would line up eventually.

Project update: Just got the heads back from the shop today, waiting for my bolts to arrive then I will start reassembly. Disassembly went well, a few hours a day for a week since I have the time. It’ll be nice to finally switch the ratchet to tighten. Wish me luck.

 

If you haven't already, see the thread here by @zguy1 here
https://www.tacomaworld.com/threads/4-0l-v6-with-bad-head-gasket-repair-or-replace.781269/

He documented his whole process there including timing, from what I recall

 

Sounds like you have figured it out. I suggest using the paint marks on the chain, mark on the crankshaft, marks on the cam gears and marks on the journals to get the motor "in time". Once the timing is set, every two rotations of the crank shaft will put the motor back in time. All of the markings will line up except the paint marks. As you have found out, you have to turn over engine many times to get the paint marks to match the initial setup as described in the service manual.

Hopefully that makes sense.

I enjoyed putting the motor back together. It is definitely easier than disassembly in my own opinion. Make sure your head bolts holes are cleaned out and that there is no fluid in them. Prepare and test fit the timing cover before you put the FIPG on there. The timing cover was most nerve racking for me.

Good luck. If you need more info let me know.

Edit: Here is picture with initial timing set including paint marks.

 

Thanks brother, that all makes sense. I just finished reading through your post also and lots of good info. So many great reads on this forum, and videos on YouTube. Timing and timing cover are my only concerns moving forward, but I’m sure they’ll come together with enough cursing.
I originally planned to post more along the way, but you and others have covered this topic very well already. Same job, just higher cost for parts these days it seems. No broken parts or anything that needed extra attention, just time consuming.

The shop that tested and shaved my heads recommended I double up on head bolt washers. He said that often aftermarket bolts are a tad longer and can bottom out with a freshly shaved head, causing leaks down the road. Haven’t seen anyone else mention this, and he took off the bare minimum ‍♂️

 

I have not but a quick check is to either measure the bolts or size them up to an old bolt... can't see them making too long a bolt because that cost them money.

 

If the standard bolt length causes a problem, then the machine shop clearly took off too much material. They’re removing a few thousands of an inch at most.

 

Thats another good point. Either that or it throws timing codes from the changed chain length

 

I agree with both of y’all, and the bolts were the exact same size, but I ended up doubling up on the washers just to be safe. We’ll see if it makes any difference.

I’ve got the entire thing wrapped up but am too nervous to turn the key, so I’m procrastinating by cleaning the air filter housing and such. Everything went together well, the timing marks all lined up, and everything moved together without much resistance so I’m feeling good. But, I need a sandwich and a smoke first.

Wish me luck

 

Have a meal and a smoke, and a coldie handy for the victory salute!

 

Are those.. Are those rocks all along the cowl under the wipers?

 

Haha yeah I’m a rock hound and that’s my traveling rock garden. Surprisingly they all just sit there, only lost a couple from a huge freeway crosswind once.

 

Finally turned the key and he fired right up. I let it run for 5mn or so, it was idling low and rough (per usual upon cpu reset), but seems to be good when I rev it up a little. I’ve got my camper set up so I can’t drive it yet but tomorrow the test drive will be about 2-3hrs NW for some work.
A couple wet spots under the rear passenger side of the head that I’m going to keep my eye on (where the extra sealant goes on the gasket), I think (and hope) that it was just residue from cleaning and resetting everything.

I’ll post an update after the test drive and include overall cost and tricks I picked up but haven’t seen mentioned.

Thanks for the help y’all, truly. Both old posts and new comments were essential in this project for me, much appreciation.

 

Went for a 2.5hr test drive and it was very smooth, but upon arrival I noticed an oil leak coming from the back corner of the passenger side valve cover (where it’s attached with a nut rather than bolt). I checked the tightness of the nut and surrounding bolts and they seemed ok, but I’ll likely have to go back in to resolve the issue. No coolant leaking so that’s good. There had to be one hiccup and this one’s not too bad, hopefully.

There was one spot on the old valve cover gasket that had a dime size drop of sealant, which I thought was odd but replicated when I installed the new gaskets. Something tells me it’s in the same area that the leak is appearing. Not sure what else it could be as it’s a new gasket and the surface was very clean before I put it on.

 

Not sure about the valve cover leak. As I recall from memory, only sealant (FIPG) needs to be applied where the timing cover meets the cylinder heads. The rest of the head surface is sealed by the gasket itself.

 

That’s what the book says too, but I also believe in leaving things as you find them so I figured it couldn’t hurt. Looks like I was wrong this time. It’s not leaking much and I don’t need my truck atm so I’m in no rush to dig in there again. Soon though.