Do your plugs look clean? See if you can get a borescope camera into the cylinder. If there is a head gasket leak or a warped head or something else causing coolant to get in the combustion chamber, everything will be steam cleaned and look very clean and shiny inside, including the spark plug tip.

You have a decision to make. ChrisFix made a good long term test video of head gasket sealers. If it's just something you need to work for a little bit before moving to a new vehicle, then you could certainly try it.

But if this has been a good vehicle and you want to keep it for some time, do the work the proper way. Using a head gasket sealer can mess with your cooling system in a way that you may never be able to truly restore it to normal.

I've mentioned before that I don't really understand the perspective of not putting money into a vehicle just because it's old.

Just my opinion, but if you've been taking care of it well, why not invest in it and make it last longer? I can understand with cars that are proven pieces of junk, but not with cars that you have taken care of and will go forever with good maintenance. If you like the car and it has served you well, why not? Treat your cars well and they will treat you well. That's always been my mindset and it has shown itself to be true.

 

First of all, thanks everyone for the quick responses.

Do your plugs look clean? See if you can get a borescope camera into the cylinder. If there is a head gasket leak or a warped head or something else causing coolant to get in the combustion chamber, everything will be steam cleaned and look very clean and shiny inside, including the spark plug tip.

You have a decision to make. ChrisFix made a good long term test video of head gasket sealers. If it's just something you need to work for a little bit before moving to a new vehicle, then you could certainly try it.

But if this has been a good vehicle and you want to keep it for some time, do the work the proper way. Using a head gasket sealer can mess with your cooling system in a way that you may never be able to truly restore it to normal.

I've mentioned before that I don't really understand the perspective of not putting money into a vehicle just because it's old.

Just my opinion, but if you've been taking care of it well, why not invest in it and make it last longer? I can understand with cars that are proven pieces of junk, but not with cars that you have taken care of and will go forever with good maintenance. If you like the car and it has served you well, why not? Treat your cars well and they will treat you well. That's always been my mindset and it has shown itself to be true.

I actually boroscoped all cylinders after starting the piston soak. I could see that they all had carbon built up entirely on the piston heads. After finishing the piston soak I scoped them again and saw that all of the carbon was removed so scoping them now and seeing clean cylinders wouldn't reveal any useful information.
I saw ChrisFix's head gasket sealer video and he got about 10k miles over 2 years more use but he used one of the ones that is poured directly into the coolant. I wonder if one where you flush the coolant out and remove the thermostat before using water and sealer would work better. They advertise a "permanent" fix which I wonder if is possible with the more thorough method of sealing. The ones I found are:
Blue Devil Head Gasket Sealer
K&W Permanent Gasket

I agree with your sentiment with keeping a good workhorse. I've been pretty good with maintenance after buying it including refreshing all fluids, changing oil every 5k and transmission fluid every 10k. The tires are less than a year old and the AC compressor was literally just replaced 2 weeks ago. However given the fact that the engine has basically already failed, and the known issues with VCM and transmissions in Odysseys has me second guessing if it will be worth it. It'll cost half the value of the car to make this repair. Going with this sentiment, would you go with replacing the whole engine at $3800 or go with the head gaskets at $3200?

If a leak down test has not been done yet, please do one before making any decisions. There are many threads about people making the wrong choices and wasting time and money.

Then I would do this - do a block test

After that I would use Bar's HG sealer (https://www.amazon.com/Bars-HG-1-Blown-Gasket-Repair/dp/B003RGIWO0).

I plan on doing the leak-down test and then maybe the block test. I'm waiting for the leak down tester and the block test fluid to come in the mail. Funny thing is I got a compression tester first to get a basic idea of what's going on but the 14mm/18mm hose doesn't fit the 12mm threads in the 2010 Odyssey. Hopefully I get everything tomorrow.

Have you had personal experience with Bar's HG sealer? I saw that it had good reviews on several websites as well. I'm just concerned that mixing it with coolant as instructed could cause more issues than the other ones that I've mentioned above.

 

If a leak down test has not been done yet, please do one before making any decisions. There are many threads about people making the wrong choices and wasting time and money.

 

IMO, $3500 is better spent as downpayment to your next car.

Then I would do this - do a block test

(https://www.amazon.com/Block-Tester-BT-500-Combustion-Leak/dp/B06VVBSFTF/ref=sr_1_3?crid=1HIYJCM2E8WIK&keywords=engine+block+tester+kit&qid=1662070045&sprefix=engine+block+tester,aps,99&sr=8-3&ufe=app_do:amzn1.fos.18ed3cb5-28d5-4975-8bc7-93deae8f9840)

And ascertain that indeed you have HG blown.

After that I would use Bar's HG sealer (https://www.amazon.com/Bars-HG-1-Blown-Gasket-Repair/dp/B003RGIWO0).

Then, will hope for the best while looking for another car.

I had this issue with Subaru. That HG sealer did not help. I junked the car after driving it with blown HG for 1.5 years
(I had to periodically to turkey baster coolant from overflow reservoir back into radiator). It was OK around town, but I would not dare to go on any trip in it.

 

Head gasket sealers will just plug up your radiator and heater core, as well as leave sediment and sealer all throughout the block, contributing further to reduced cooling. It will just make a mess of it. A head gasket replacement isn't cheap but if you put the sealer in it the engine is toast.

 

That's the fear behind it all. But being that the new engine is about the same as the cost of the gasket replacement, toasting the engine with gasket sealer seems like maybe a risk worth taking. The question is how badly will it clog the radiator and heater core?

 

No way an engine replacement is the same cost as a head gasket replacement. Besides, a used engine comes with inherent risks...you don't know any history of the used engine and what happens when it's started and has a problem. Personally, I'd do the head gasket if that's what it needs.

 

After doing a compression test I'm 99% sure it's a head gasket. Here are my compression numbers:
L M R
Rear Bank 200 225 205
Front Bank 195 195 205

By themselves it doesn't seem like a clear indicator. However while doing the test I found that cylinder 2 (rear bank, middle plug) spewed blue coolant when I spun the engine. Also when boroscoping that cylinder I saw coolant in the spark plug hole and the piston head appeared to be soaking wet (thus the higher compression). I also saw a few drops of coolant in the spark plug hole for cylinder 1(Unsure if I have the numbering correct, but it's rear bank, rightmost plug) and the piston head appeared to be damp but not as wet as cylinder 2. All other cylinders appeared to be bone dry.
Soooo, to me this sounds like a confirmed head gasket on the rear bank. And it seems like cylinders 1 and 2 (rear bank, middle and right cylinders) are the main culprits, which would be consistent with the P0301 and P0302 codes. So onto the solution...


The costs aren't exactly the same but it appears that my local mechanic won't do just the head gasket and they only charge $600 more for a new engine than Honda charges for the head gaskets. Also, as I bought this car used, I don't really know the complete history of this engine either. I only know that this engine lasted me a little less than 2 years. So I guess it would be a wash with the new used engine.

Or if you're feeling adventurous and confirm you do need a head gasket, maybe try a DIY job. It will be a little more challenging since it's the rear bank, but If you're thinking of getting rid of it because of this, there's nothing to lose by trying it first. Best case scenario you save yourself a ton of money and have a good van again, worst case scenario you just get rid of it, which you were going to do anyway.

If the DIY path can be done without removing the engine I'd be willing to try it. Seems like it would be nearly impossible for the rear bank but if someone can absolutely confirm that it can be done with the engine in place and someone can offer some kind of tutorial for how best to do it I would like to try it. I believe I would still need to send the head for machining, is this correct? What's the best way of finding a machine shop and how much does it generally cost?

If DIY can't be done with engine in place, I'd probably go the head gasket sealer method first

 

I suggest calling more shops for head gasket quotes.

 

I also called Pep Boys and they quoted me $2460 for doing the head gaskets. However I'm not sure I trust them to do a good job with it. My local Pep Boys even lied to me about rotating my tires so I have trust issues there.

 

Or if you're feeling adventurous and confirm you do need a head gasket, maybe try a DIY job. It will be a little more challenging since it's the rear bank, but If you're thinking of getting rid of it because of this, there's nothing to lose by trying it first. Best case scenario you save yourself a ton of money and have a good van again, worst case scenario you just get rid of it, which you were going to do anyway.

 

IMO, and here I am in agreement with OP's mechanic. The HG job has to be engine out, machine shop to get it right. Normal advice is to get a junk yard engine which you can check with boroscope for HG failure and install that engine. If were doing DIY, this is the route I would take. Risk of unknown engine. I would minimize it with applying as much knowledge I have + the observations and measurements I can make.

As for whether or not "stop leak" will "gunk things up" .... The logic is this - the car is goner give or take, so if "stop leak" kills it, then there it goes. Doing a complex DYI just to junk it later on - it better to sell the car as is before you took it apart. I am not advertising "stop leak", and do not blame me if it goes bad..... FWIW I put it into a Subaru and it did not harm whatsoever (no it did any good). I did not even replace thermostat (some fear it get clogged and never opens, did not happen to me). I believe t can't fix internal leak - pressure is to high. But some people report success.

 

No, the head gasket can be easily changed with the engine in the vehicle. No need to pull the engine for head gasket, unless the block is warped...never heard of it on these engines, though.

 

aren't you supposed to machine the block? Else you do all the work just to discover (possibly) that the leak is still there?

 

Generally you always machine the head after it has been removed, but not the block. A head gasket job would be considerably more expensive if the block had to be machined.

 

Book time for the rear head is 10.8 hours. R&R of the engine is 15 hours but a heck of a lot of work as it requires the engine and trans to be dropped out the bottom. Not everyone can do that DIY in their garage. Head gaskets absolutely, 100% can be done in the car and with some decent tools. They are done all the time after timing belt failures and all the piston ring jobs that the dealers have done.

 

Oh, and yes, it's pretty clear you have either a blown head gasket or cracked head. You could go one step further with a cooling system pressure test and your borescope and see if you can see where the coolant is coming into the cylinder from.

If you can find a used engine with significantly fewer miles for not that much more money then it might be worth swapping the engine. Otherwise, DIY the head gasket if you have the skillset and tools.

 

I still suggest a leak down test but if you are ready to DIY then go for it. Rings can be done without removing the block. Good luck!

 

Thanks for the video. Is the amount of space to work with similar to the Odyssey? I feel like the space in the Odyssey is a bit more cramped for the rear head.
I was going to do the leak down test since the tester arrived in the mail this evening. However the tool itself was leaking air and I ran out of daylight. Also, this might sound like a stupid question but what is the best way to spin the engine manually to get a piston TDC? Things look a bit tight and I was going to try to use a serpentine belt wrench to reach down there from the top side but it doesn't arrive until next week. Would it be better to remove the plastic shields on the bottom and reach upwards instead?

 

It's probably easier on an Odyssey. The Pilot engine is deep down in the engine bay and, in my opinion, more difficult to work on the back head.

For spinning the engine you will use the crank pulley bolt and a breaker bar/large ratchet, accessing from the wheel well. You will also need a way to get that crank pulley bolt off. That's one of the biggest challenges of the timing belt job, which you will need to do in order to pull a cylinder head.

 

If you are planning to DIY another option is to source a used engine and install it yourself. Just a suggestion.

 

No way. That is a huge undertaking as the entire engine and transmission drops out the bottom with the subframe. I have a lift and it's not really something I'd want to do if I didn't have to.

 

I used the Lisle socket and a plug in impact rated at 440lb-ft. The crank pulley bolt came off liike butter. South Main Auto has YT videos on J35 head swaps.

 

That's what I use along with my Milwaukee high torque impact but not everybody has that stuff.

 

The worst part about working on the rear head is the wiring harness that goes across it.

 

 

Even if you don't have the tools, it may be worth investing in with the money you'd save by doing this DIY. As for the machining, it wouldn't hurt to look for some local machine shops and give them a call and ask.

 

Doing some planning before I attempt this larger project. I'm reasonably mechanically inclined but I'm not well versed in a project this big. One concern is that I somehow screw this up and I'm out the cost of parts ($370 for each gasket). Are there certain difficult / risky parts that I should watch out for? Or any pointers on avoiding major problems? I'm guessing the main concern is botching the timing belt and causing more engine damage since it's an interference engine. I guess one way to check is to turn the engine manually to feel for any valve collisions.

Should I do both head gaskets while I'm in there or is that unnecessary? My guess is that I might have to remove the front head to get enough clearance for the rear head.
Are there other things that should also be done while the engine is open? I'm thinking at least water pump & timing Belt and valve adjustments.
Also what are the chances that the piston rings on the rear bank are seized? I'm hoping the piston soak would relieve this issue but not sure of efficacy.

 

Or any pointers on avoiding major problems? I'm guessing the main concern is botching the timing belt and causing more engine damage since it's an interference engine.

My guess is that I might have to remove the front head to get enough clearance for the rear head.

Set # 1 to TDC then place MARKS on the timing belt that align with the marks on the front cam, rear cam and on the crank with a dab of paint or fingernail polish before you remove the belt.

You will have enough space to remove the rear head without having to remove the front head.

There will be 2 metal alignment dowel pins on the lower right and left corners, don't lose those. They might come out with the head, they might stay in the block, either way, don't lose them and make sure they are in place before you put the head back on.

The service manual is extremely useful.

 

There is a gamble with anything you do but your compression is good so I don't suspect any ring issues. As long as you take your time and follow the service manual I think you'll be fine. It's not inherently difficult, just lots of disassembly and reassembly. Without the right tools the crank bolt can be frustrating. With the right tools it's not even an issue. Be sure and follow the proper sequence for removing and installing the head bolts. You'll want a full Aisin timing belt kit and a full gasket set. There are a lot of misc gaskets and o-rings that will be necessary to replace when you get down that deep. Also, it's recommended to replace the head bolts.

 

Consider getting a service manual to help you out.

 

You need to research how to set the timing of the timing belt. I do not think the front head needs to be removed to work on the rear head. The intake manifold needs removal before taking off either head. Agree with obtaining the service manual.

HELP! Here is a fun one for you - Crank turned without...

Helping my neighbor's son navigate through his first timing belt/waterpump swap. Everything was going good until I noticed he was turning the crank and the timing belt was not moving, just the crank bolt. I discovered He had accidentally dropped the woodruff key when he put the crank pulley...

www.odyclub.com

 

A year subscription to AlldataDIY would be a good option for this.

 

Had similar issue with my 2007 Honda Odyssey. Van overheated and oil in the coolant and vice versa. Took both heads off and had them inspected and machined by a machine shop and they pressurized it and found that the front head had a crack somewhere you couldn’t see. Rear head was fine and reused it. I bought a rebuilt cylinder head from rock auto and at the time it was about $500 with a core return I also did what others mentioned…new timing belt, tensioner, thermostat etc…..the van has been running great since then put over 20k on the engine with the new head and head gaskets. Bought most parts they rock auto. It is a big job. Seemed like the hardest part was getting the rear head lined up and setting it down on the block. You’ll also have to do a valve adjustment on the new head and would recommend it done any way on the other head.

 

Thanks everyone for the input. After some consideration I ended up trying the K&W Permanent Head Gasket Sealer. After going over reviews online and on Amazon I didn't see any negative reviews that indicated causing other issues. Just a few saying that it didn't work. To me this seemed like a low risk and cheap attempt to fix the issue.
I went through the whole process of removing the thermostat and flushing the coolant 8 times with water to make sure there was none left that might negatively impact the gasket sealer before using it. I also removed the spark plug to the main culprit cylinder, and ran the engine for 20 minutes. At first there was a lot of white smoke. But to my surprise after 20 minutes it seems to have worked its magic so far without causing other issues. I also changed the oil in case there was some coolant and/or gasket sealer that had transferred from the cooling circuit into the oil. I'm still going through some flush cycles with water to make sure there are no residual particles that might cause blockages later. And I need to reinstall the thermostat and re-add coolant. But right now there is no longer any white smoke at the exhaust and doing the block leak test with the blue test fluid shows there is no CO2. Also I boroscoped the previously leaking cylinders and they both seemed to be dry after about 20 miles of driving. I'll report if this "permanent" fix falls apart, at which point I will re-evaluate my options.
Thanks again to everyone for your input. I know if may be disappointing to some to have gone with the cheaper fix but for me it was worth the try and seems to have paid off for now.