4.0L V6 with bad head gasket (repair or replace?)

Hi all.

I haven't posted here but have been a lurker on this site for sometime. I am a 4Runner owner and I originally came here as I was interested in replacing my stock wheels with used Tacoma TRD wheels.

Anyway, I figure I would go ahead and ask on this forum as the both the 4Runner and Tacoma share the 4.0L V6.

I have a 2008 4Runner with the 4.0L. I bought the truck used with 206k miles and it now has 295k miles. I have maintained the truck during my ownership. I have never had an engine problem or check engine light. Recently I noticed that I started losing coolant with zero visible leaks. I suspected the head gasket but was under the impression that engines from this year did not have head gasket issues. The truck runs great and does not appear to lose coolant while doing short drive around time.

I confirmed that the head gasket was leaking by pressurizing the cooling system and proceeded to look in each of the cylinders for coolant leaking in with an inspection camera. I found that both cylinders 6 and 4 are leaking.

I understand that there are only 2 viable options aside from selling the truck as is.

1) Replace the gaskets
2) Buy a used motor.

Since I would be doing the labor for the 1st option, I am tempted to go that route.


Thoughts / Opinions? Thanks!


Btw, I have watched the Gasket Makers video as well as the Mayo Cars DR video too. I believe I have located the best videos on this issue so far. If I repair the head gaskets. I plan to install new gaskets, seals along with new head bolts. I do not plan to replace the timing chains or tensioners unless something looks suspect. I would like to get the heads cleaned up and have the valve seals replaced. The car does not puff any smoke on startup even after sitting for sometime. I assume that means that I do not have a valve seal problem currently.


EDIT: 12/28/22
- I ended up replacing the head gaskets. See post #118 for a summary of information, parts and tools that I used for this repair.

 

I'm in the same boat with mine. I did an engine oil analysis with blackstone and when I got my results it showed trace amounts of coolant in the oil. I also had some unexplained losses in coolant and a gurgle sound from behind the dash. Personally i'm leaning towards finding a new motor, but its tempting to replace the head gasket because everything else in blackstone's report indicated the motor is doing just fine for the most part. If you go ahead and change it yourself it'd also be a good time to change the water pump out too while everything is disassembled.

 

With 295k, I’d look for a low mileage used engine.
Or replace the timing change and components if you choose to keep your engine.
And hope the rest of the engines is in good shape.

 

I recently did both my HG's, all new timing components, and installed aftermarket URD exhaust cam gears. The overall job was basic and pretty simple with no surprises popping up. The way that Toyota does the timing marks makes it nearly impossible to incorrectly set timing.

Toyota has a gasket kit that includes all the gaskets needed including valve guide/stem seals, there are also aftermarket kits available as well.

I found this series of detailed youtube vidoes for the 1GR-FE that I found helpfull and used as a quick reference at times ...

https://www.youtube.com/watch?v=5RgFlfTmsMA

 

Thanks for the response. For timing chain components, are you suggesting replacing the timing chains (2 cams and main), 3 tensioners and timing chain guides?

Thank you. I did find the Mayo Cars DR video as well. Your post may have given me the extra push to take on this job as it appears that you have over 300k miles on your motor after going through your build thread. What did you spend for all of your parts to do the job? Gaskets, seals and timing components?

I am feeling more confident about the job but have concerns for the following steps.
- Removing the harmonic balancer if my heavy duty impact will not remove it. I have seen folks put a breaker bar on it and bump the engine over. This seems sketchy.
- Installing the harmonic balancer. Not sure how to hold it in place when torquing it down.
- Installing the sealer on the head gasket and surfaces. Don't want to mess that up.
- Installing and sealing the front timing cover while keeping the oil pan installed. Looks tricky.
- Finding a good machine shop locally to check and clean up the heads plus install new seals. Mine don't appear to be leaking but it seems like a wise thing to replace since the head is out.
- Removing the rusty and crusty exhaust manifolds from the heads once they have been removed from the truck.

Maybe those steps above are easier than I think...

 

Yes, you’re going in that deep for the most part anyways.
Might as well to them.

 

Something I've learned over the years wrenching for a living is to replace all timing components on high mileage motors. Chains stretch, tensioners become weak and loose tension, plastic guides become worn/brittle, sprockets/gears become worn etc..

At the most minimum, I would only recommend all 3 timing chains, main tensioner and guides. I would highly suggest to replace the crank shaft and idle sprockets, and the other two tensioners all at the same time. Spark plugs would also be recommended to be replaced. This would also be a good opportunity to replace the coolant bypass/heater hoses, water pump and the drive/serpentine belt.

My 1/2" Dewalt Cordless had no issues breaking the Crank Shaft nut loose, I believe it was a 24mm socket.

Installing the Harmonic Balancer was not an issue, it's not pressed on like Ford or GM's are. I also didn't' use a torque wrench to set torque, just a couple of presses of the trigger of the impact was all that's needed for me. I have installed many over the years and I know what the feel is. If you're inclined to set proper torque of the crank shaft bolt, I would recommend leaving the valve covers off and locking the cams with a locking block or with the help of a buddy to hold a wrench on the cams. The size of the wrench to hold the cams would be a 24mm. A new Crank Shaft bolt is highly recommended!

Applying sealant to the heads/block in a precise spot isn't as critical as you may think it is, just mimic how it's done in the videos and use the work shop manual as a reference.

The Oil Pan doesn't need to be removed.

I did a few practice runs of installing the front cover on and off without sealant applied, mainly to align the Oil Pump to the Crank Shaft. The Front Cover goes on easy once the Oil Pump is aligned.

Soak the exhaust manifold studs/nuts with a good amount of WD-40 as well as the exhaust studs/nuts prior to removal. I was lucky that my exhaust hardware was in good condition and replacing with new wasn't necessary.

I also use WD-40 on all electrical connectors when disconnecting, something that I've learned over the years.

The regulars in this thread will also be extremely helpful and will offer sound advice
https://www.tacomaworld.com/threads/trd-magnuson-4-0-supercharger-tips-tricks-and-mods.518932/

here's a basic spread sheet with prices and part numbers that I made up as I was collecting my parts.. use this as a reference
https://1drv.ms/x/s!AmLTJpokHaPTgU0oi9aiLlZTgQwS?e=HojHrd

 

Thanks a bunch. That spreadsheet is very helpful. I do have a new set of spark plugs ready to be installed. I will also be changing the water pump and thermostat too. I have never changed them in the past 3 years / 90k miles that I have owned the truck. I plan to spray all the rusty fasteners and bolts prior to disassembling them. I will attempt to remove the exhaust manifolds from the heads once they are out of the truck.

I did find a local machine shop today and they sound very reputable. I will have them check the head for trueness and damage plus check for leaks. I'll decide on how much more I want to do to them once they have been looked at. They also recommend resurfacing the head at the very least.

 

So I made some more progress tonight. I was able to remove the lower intake and the passenger side valve cover. It's definitely slow going for me. I am trying to take pictures of everything so that I can figure out where everything goes when I put it back. I also loosened the harmonic balancer bolt by bump starting the truck while using a breaker bar. This was a bit sketchy but it turned out to be very easy.

This is where I ended up tonight. I got stuck on trying to remove the clips that are noted with the 2 red arrows in the bottom of the picture.


A close up of one of the clips on the power steering pump. I am tempted to break that off.

My lower intake looks pretty greasy and oily. Is that normal for a truck with almost 300k miles?

 

Those brackets typically have a little tang on them you gotta hook with a small flat screwdriver to unlatch.

The intake looks pretty normal, the buildup is from crankcase vapors.

 

Thanks.

You were right regarding the clip. After starting fresh yesterday, the next day, that clip came right off. Sometimes it really does help to walk away for a bit when you are stuck on something even when it is a ridiculous plastic clip when compared to the whole job.

I made some more progress. Pulled the right valve cover, pulleys, power steering pump, alternator, oil filter housing and water pump. I did notice on the water pump that there was a bunch of crud by the weep hole. Not sure if that is normal or if it was leaking slowly. The weep hole is hidden behind the fan pulley so you would never know it unless it leaked out.

Next step are to start unbolting the compressor and then attempt to pull the timing cover.

 

Yes. It was.

 

So I got a little further today. That A/C compressor and bracket kicked my but. I was able to get them off. I got the harmonic balancer bolt off days ago but didn't try to remove the pulley itself. I tried pulling on and gently prying. I'm guessing it is stuck on there with rust or something.

Any suggestions on how to get the harmonic balancer off? I am going to try and see if my local Autozone rents a puller for that.


Also, I pulled the driver's side valve cover off and it has more oil / carbon build up underneath as compared to the passenger side.
Is that normal?

 

Use a puller. Make sure it doesn't press into the threads of the crank.

Personally what I do is spray a penetrating fluid into the crank pulley, and tap it in and gently pry it out, working it free.

As for the valve covers its not a big difference, but side to side will have slightly different blowby and the PCV valve is on only one side. It's definitely not abnormal.

 

So I rented a puller yesterday but it turns out that it did not have the correct bolts to thread into the harmonic balancer. I believe the harmonic balancer requires M8 x 1.5 bolts whereas the kit came with M8 x 1.25 ones. I ended up tapping on the harmonic balancer with a rubber mallet and it came right off.

After that, I was able to remove the timing cover, timing components and the cams out of both heads. I removed the head bolts on one side. I had to put a piece of pipe on my 1/2 breaker bar to break the head bolts loose.

Are they as tough to put back in?
If so, I might want to get a bigger breaker bar.

The plan tonight is remove the head bolts from the remaining head and finally get the heads out. I'm curious to see what the gasket looks like on cylinder #4 and #6.

 

Good job on the progress!

I agree with removing the head bolts, they were pretty tough. They install a bit easier, just make sure each bolt is properly covered with motor oil when installing.

Here's a tip .. use compressed air with an air nozzle to blow out coolant and any debris in each head bolt hole before installing the head gasket , head and head bolts.

 

Well, I finally got both of the heads out tonight. A friend of mine was supposed to stop by to give me a hand lifting out the heads but he bailed at the last minute. Being the impatient person that I am, I just went ahead and took them out myself. I was expecting them to be heavier than they were considering the exhaust manifold are still attached.

I am going to attempt to loosen the exhaust manifold bolts tonight. I sprayed them a couple of times tonight with PB Blaster.
Anyone have any other suggestions on what I should do before I attempt to put impact on them?
I know I am going to the machine shop but I really don't want to intentionally break them.

Regarding the blown head gasket, I was expecting to find some obvious issue with driver's side one but I honestly can't see any issues by casual observation.

There are a few things that are still bugging me considering that I have never done something like this involved before.

1) How do I clean the cylinders, walls and the top of the pistons? I'm not too worried about the carbon buildup on top of the pistons as that is probably cosmetic anyhow, but I do have some debris, oil and antifreeze in them after lifting the heads off of the block itself.

2) How much surface prep on the block do I need to do? Do I need to get a machinist level to check for trueness? Not sure what that would accomplish considering I couldn't do anything about it if it was uneven.

3) Head bolt replacement. I guess this is one of those topics that there will never be consensus on. Some say to replace and others say to keep. The FSM says to check. I measured mine and they all fall within the range 10.72mm to 10.85mm. The FSM claims the minimum is 10.7mm.

I really want this job to be successful considering this truck has been all over the US with no major issues. I would like to make this truck road trip worthy again.


Driver's side block w/ gasket


Driver's side block w/o gasket


Heads removed...


Driver's side head...

 

I use brake clean and WD-40 along with a simple small wire brush and a small 2" putty knife to scrape and clean off the carbon from the top of the piston heads. Compressed air to blow off debris that a shop rag can't get and to blow out what collects around the piston rings. It's a tried and trued method I've been doing throughout the years. You have seen the pics in my build thread, method works well. Bring each Piston to TDC one at a time and go to town.

My leak was happening at #4, and all it took was a bit of brake clean on a shop rag and a few wipes, very little use from the wire brush was needed.


When I prep a block for heads, I use new razor blades ( I go through a few of them during this process) to scrape off the left over material and what ever carbon build there is. I use light pressure with the blades and at an angle that is almost flat to the surface because I don't want to score, gouge or cause any scratches , goal is to remove carbon and old head gasket material. Spraying Brake Clean on the area being worked helps a bit too. After the bigger stuff is removed, I'll use the tips of my fingers to feel what needs attention using a peace of a 3M Scotch-Brite Pad. Once you start, you'll get a good sense of the process and what's needed. All it takes is just a little patience and a few minutes to achieve perfectly acceptable results. I wouldn't be worried about trueness of the block unless you get word from the Machine Shop that the head(s) are really out of whack.

The Block front sealing surface and timing cover sealing surface needs to be absolutely free of any old sealing material, otherwise a proper seal won't happen, and oil leaks will occur over time. A razor blade(s) at the right angle (exactly like when doing the Block Deck) as to not score the surface works will at removing the bigger peaces, a 2" putty knife can work well as well. I say 2" putty knife only because it's what I've been using for some time now. A 3M Scotch-Brite Pad works best after the bigger peaces have been removed. Use brake clean or similar cleaner on the surfaces right before applying whatever silicone sealant you use. I would suggest to put some rags on the bottom of the oil pan to help block any falling material

On each side of the block is a little peacock/ drain plug thingy, use a 10mm socket or wrench to open. Don't be afraid to fill those coolant passages up with water/cleaner with the plugs open to help clean/remove all the crap from the cleaning of the piston heads, deck surface, left over coolant and oil. Toyota made this part easy!

Before final assembly, I would suggest to spray brake clean or similar into the exposed oil pan before installing the front cover with the oil pan drain plug removed allowing all the junk to drain out.

For extra Credit, add 2 - 3 quarts of less expensive generic motor oil after the front cover is installed with the oil pan drain plug installed. Remove drain plug to allow the oil to drain, sometimes this method will help remove whatever if anything that may be in there.

For the exhaust nuts, try using an impact to break the nuts free.

Never ever..ever Re-Use Head Bolts on a high mileage vehicle! Unless it's a complete shitbox of course..

 

Thanks again for the detailed response. I spent a few hours over the past few days working on cleaning the heads. As far as progress goes, I am moving very slowly. Nobody would pay me to do this job as it seems to be taking me forever. .

I am still waiting for my parts order. At the moment, I just have the gasket kit, head bolts, FIPG, water pump and thermostat on order. I'm still pondering what timing components I will replace if any. I don't believe I will replace my older working Toyota parts with aftermarket ones to save a few bucks.

Anyway, back to the job. I did get the exhaust manifolds off. I soaked them with PB blaster multiple times. My impact got all but one nut off. The nut got rounded off so I heated it up and tapped a SAE socket over it. I used my impact and it came right off. I don't see how these bolts could be removed on rusty manifolds while in the car.

I degreased both heads and removed the oil valve filter. The filters were very clean. I cleaned the heads using a combination of carb cleaner and brake clean. The combustion chambers look cleaner but most of the carbon is still there. I made a first pass with a plastic razor blade on the gasket areas. Prior to the cleaning, I removed the lifters and labeled them accordingly.

I have yet to clean the cylinder block surface or pistons. I may try to remove the block drains today as you noted and clean out the remaining coolant. For cleaning the pistons, have you ever tried to put grease between the piston and cylinder walls while at TDC? I heard this helps catch any debris before it gets stuck in the ring area. I also heard about folks using shaving cream in the coolant passages to catch debris before it falls in. Not sure if these techniques are gimmicks or really work.

Also, I noticed a rough edge between the top of the cylinder block and the piston when at TDC. Does carbon build up here too just like on the combustion chambers on the cylinder head? This seems like an area on the block that should be left alone assuming it is below the deck.

 

Clean until you can't feel the old material with finger nail. No further. Toyota gaskets are very forgiving.

I use razors, scrapers, emery cloth and a high speed wire brush. I use intake cleaner over parts cleaner as its stronger, but both work.

Ideally you'd check the head and block with a straight edge, but they are expensive.

I only send out heads that overheated or fail the straight edge test. I rarely send out v6 heads.

Also, now is the time to do valve seals, time consuming the first time but its much easier when the head is off. Plus you can inspect valves and clean them.

The ring of carbon on the top of the cylinder is normal, clean gently, but don't fret about it.


Ps re use the headbolts if you want, I’ve reused hundreds. But you sound concerned so it’s not a bad idea to order a set for peace of mind