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

I didn't see it metioned but keep your valve buckets where they belong otherwise all your valve clearances will be off.
It would be a good idea to check them anyway while you have it apart and adjust as needed.

 

Any suggestions on what tools I need to change the valve seals? I have gone this far so I am sure I could do those as well.

Regarding head bolts, I was "pretty confident" that I was going to use my old head bolts but heard from many folks not to do so. Since this job is so time consuming I just opted to purchase them. Keep in mind that they all measured above the minimum specification that the service manual calls out. For what it's worth, even "Mayo Cars DR" responded to a post on one of his videos and said reusing bolts are fine. I assume he has done more engines than I will ever do. I have also seen several receipts from folks who had this repaired at a dealer without bolts being changed. In the end, there is no end all answer to this question so I stopped looking for one and bought them.

 

I did remove and cleaned them. I also labeled them accordingly. I ordered a straight feeler gauge and plan to check them after the cams are installed. Hopefully I don't need an offset one. If so, I will need to return that.

In hindsight, I wish I would have measured a few of them prior to disassembly. Practice make perfect I suppose, but unfortunately this job is very involved and time consuming.

 

This https://www.lislecorp.com/specialty-tools/valve-keeper-remover-and-installer (search for it on Amazon or locally)

or rent / buy one of these

https://www.toolsource.com/valve-sp...valve-spring-compressor-overhead-p-70683.html

Alternatively, you can send your head to get machined and they can change the valve seals for you.

 

Thanks for the tool suggestions. I am bringing them to the machine shop to get checked and possibly resurfaced if needed. I did ask specifically and they said changing the seals would be considered part of a valve job. This is why I figured I would change the seals prior to me bringing them to the machine shop. This way it almost like someone indirectly checking over my work.

 

@Bishop84 what are your thoughts on the rumor that milling the heads on a 4.0L can cause the cams to be out of time enough to set timing codes?
I had someone ask me about it the other day and I've seen several references to it on the forums but I've yet to see any hard evidence of it being true.

 

I got asked it as well and got ghosted lol

I think its malarkey, it does affect compression and will slightly change timing, but the truck can handle the tiny changes.

I never mill 3 cylinder heads though, so who knows. But I've yet to see it cause issues on any inline 6 or 4 cylinder head I've had machined.

 

I was thinking about this after you guys asked the question to each other and I can't see how it could affect timing. If you mill or resurface the heads, that would bring the camshaft timing gear closer to the camshaft sprocket which is the same as adding slack to the main timing chain which could also be introduced by the wearing of the engine timing chain tensioners. This slack is taken up by the main chain tensioner. Adding slack via a stretched main chain is different as it could cause timing differences between bank 1 and bank 2. Milling or resurfacing the head would impact and theoretically increase compression since the combustion chamber is gotten smaller albeit a tiny bit.

 

Update here. Looking for some feedback.

I just heard back from the machine shop. They said the heads do not have any cracks but will need to be resurfaced as they are warped. They said this is typical of an aluminum head with that many miles. I believe they said it was out .003 which is out of spec according to them. They also said that several intake and exhaust valves were leaking. I believe it was 5 intake and 2 exhaust valves.

The machinist there said that doing a valve job would be expensive and recommended that I remove the valves and clean them up. He didn't recommend a valve job considering the miles and that I would most likely need to adjust the valves after.

He suggested that I replace the seals, gently wire brush the valves and use oven clean on them if needed. He also suggested that I lap the valves after. At that point I would bring the heads back and he would resurface them for me. This way there is no risk that I would mar the surface while working on the heads.

I'm not sure how to proceed. I'm hung up on the fact that there are valves leaking and that I am leaving it alone. I guess it is reasonable to expect the valves to be leaking considering the mileage on it.

Does his recommendation make sense and sound reasonable?

 

Yup, buy or rent a valve tool, remove them send heads out. Wire brush valves.
Don’t worry about lapping.
Replace the seals after it returns from machine shop.

 

It’s true.
It does, unless you have custom gaskets made.

Apparently .030 is too much
https://www.tacomaworld.com/threads/how-to-ruin-a-1gr-fe-mill-the-heads.572758/

 

I wouldn't have chucked a motor over a HG either. If you get a junkyard motor you may get stuck with some unknown issue. At least this way you know your lower end has no problems and you HG and timing stuff will be good for another 300k.

 

The machine shop dude who did my heads back in August claimed that he took off .003/.004 from each head. I installed the URD Exhaust Cams, all new timing components to include Crank Shaft Sprocket, Idle Sprocket, Toyota Valve Stem Seals and used Toyota OEM Head Gaskets when I put everything back together, haven't had any timing related DTC's yet. Tomorrow I'm doing the first oil change since the head job, we'll see how that goes lmao....

 

Some more progress.

I finished up the passenger side head. I wire brushed and lightly lapped the valves. I also replaced the valve seals. The exhaust side seals were tough to remove but the intake side came out very easy. I reinstalled the valves which took sometime due to the keepers. Two of them popped out and were almost impossible to find. Everyone warned me of that but until you actually install them you don't realize what it takes to make them pop out. Once all the valves were completed, I installed the spark plugs and turned the head upside down. I poured water into the combustion chamber just to see if any water leaked into the intake or exhaust ports.

Last night I started working on the driver's side head. The exhaust valves appear to have more carbon on them as compared to the passenger's side. I also noticed that they are a bit narrower or worn right under the chromed part of the stem. I also noticed that there is some really tough carbon on some of the exhaust valves right below the area that rests on the seat. Whereas the passenger side exhaust valves didn't appear to have that.

How could one head look so different than the other?
Even the piston tops on the driver's side have more build up. Makes me wonder if the driver's side head sees much different temperatures than the passenger side.

Anyway, here are some pictures of the exhaust valves from the driver's side. They have been cleaned up similar to what I did on the passenger side.

Is there a noticeable issue with the exhaust valves?
Do I keep with the plan of lapping the valves, changing seals and resurfacing them?

Let's face it, pouring water to test for leaks does not guarantee that they will not leak air. Also, what if I get some seepage using the water technique after lapping them?

 

Those look fine, actually better than most I see. I'd carry on.

The cleanest valves I've ever see was a head job I did on a propane 4.0. MAN WAS IT CLEAN. Like brand new inside!

 

If you’re going to have the head surfaced. Note the amount they remove. You’ll have to run a thicker headgasket or the timing will be ever so slightly off


Toyota technically doesn’t give acceptable specs for re surfacing

some get lucky, some don’t. If only one is surfaced one side will be slighly off time vs the other

 

Thanks. I have 4 more valves to reinstall on the driver's side head tomorrow. If all goes well, I will drop them off at the machine shop then. I will be sure to reinforce about removing as minimal material as possible plus recording what was taken off.

 

I dropped the heads off at the machine shop today to be resurfaced. I should have them back in a few days.

In the meantime, I was thinking about the process of checking the valve clearances once I get the heads back. Is there is a way to check them with the heads off of the car. I am trying to minimize the time working outside in the garage as it is starting to get cold where I am located.

Is it possible to install the cams as outlined in the service manual and then check the clearances? I could prop the heads up and support the sides of them to allow the valves to open and close freely.

I keep thinking that the valves will be out of adjustment due to the lapping performed and wear from the higher mileage. Of course I could do this on the motor but that sounds like I would need to install the timing components to do the initial checking only to disassemble everything just to replace any out of spec lifters.

Is this doable?

 

I set valve lash with the heads off when building a 3.4. Just torque them as spec’d. Much easier without those pesky pistons in the way

 

I got the heads back from the machine shop earlier today. I am going to install the cams tonight and try to measure the valve clearances with a feeler gauge. I have a micrometer on order to measure the current lifters if any of them are out of spec. Unfortunately I don't expect that to arrive until tomorrow sometime.

Btw, I left the cam sprockets installed on the cams when I removed them during disassembly. Hopefully they will not make things tougher when installing them for the valve check and during the actual reassembly of the motor.

Here is a pic of the newly resurfaced heads. They removed .0034 from the passenger side and .0035 from the driver's side.