Head gasket on Nissan 2.5l engine Update

2006 Nissan Sentra SER Spec-V, just over 100k miles. It started loosing coolant, just a little, on each drive cycle. The engine never overheated because it never lost more than a pint at the most. Only specified coolant has been used and it has been changed more frequently than the schedule calls for. Pulled the spark plugs and found coolant pooling on top of the #2 piston.

Engine is out and the cylinder head off. Both the cylinder head and the block are perfectly flat, no warpage. But the head gasket does not appear to have been breached either. I know if you catch them early enough, they may show little signs of a breach, but in looking at the gasket, it seems like there was a lot more coolant in the #2 cylinder than there should have been.

I have ordered a magnaflux kit but it will take a few days to get here. I am wondering what are the odds of a crack in one of the intake ports or around the intake valve seats of the #2 cylinder.

Opinions, suggestions, experience with this engine. BTW, this engine does have a history of blown head gaskets at just over 100k miles, similar to Subaru.

How do you plan to magnaflux an aluminum head?


You need a dye penetrant kit for aluminum.

You could have tested the coolant before pulling the engine for combustion gases.

Try removing the coolant from the cylinders and look at the piston tops. If one is a lot cleaner than the others, there is your “smoking gun” for a coolant leak.

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A multi-layer stainless steel head gasket won’t breach like a composite gasket, these are tougher than the cylinder head. Check the cylinder head and block with a straightedge.

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Considering there should be NONE, any is more than there should have been.

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No experience w/that engine, but on some engine designs the intake manifold has coolant flowing through it, which could conceivably leak coolant into a cylinder when the car was parked overnight and the intake valve for that cylinder happened to be open. Have you removed the intake manifold and checked its gasket?

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Magnaflux die penetrant kit.

Number 2 piston top looks like it was steam cleaned, the others have a very thin layer of carbon.

Did that, perfectly straight.

Just did that today. Looks good. This engine does have a mini radiator looking thing in it but the coolant enters it through small hoses which were disconnected years ago. My son dd not want any extra heat in the intake charge. It has a CAI.

More news, we were reinstalling the cams to get ready for the die penetrant test and the exhaust cam broke. It’s a Nismo S cam and no longer available. I cant believe that a cam that costs as much as these did were only cast iron and not billet cut. I found an almost identical set of cams that are billet cut and about $100 cheaper than the Nismo cams were.

Edit: I do not know why the answer to @Mustangman is in such large letters and apparently bolded like that.


See if you have # or ## and a space in front of your answer to him…You can check for it in the pencil edit thingy…

Large print ignored… There is your confirmation of a blown head gasket and where you should look carefully for any damage to the head or block.

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I have to admit, this caught me off guard for a second before I realized he was referring to a dye kit. The old codgers (speaking for myself) associate the company name with the original process used for ferrous metals. They trademarked it way back when. Kind of like Kleenex for facial tissues. The same company now also sell dye kits for both ferrous and non-ferrous metals. So when I hear Magnaflux I still think of the original process…


That was it, I put an octothorp in front of the 2, replaced it with the word “Number” and it went to normal.

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OK this is getting weird. Both the block and head are perfectly flat. I Magnafluxed (dye penetrant) the #2 combustion chamber and ports, no cracks. This was the only cylinder that showed signs of a leak. No carbon in that cylinder and coolant would pool in it after cooldown.

However, even though the #3 cylinder did not have any signs of coolant getting into it, the #3 exhaust port did. Because my son had tried one of those so called head gasket repair chemicals, I could see residue on the faces of the exhaust valves and the #3 exhaust port was full of the residue from the sealant. When I wiped the inside of the port with a rag, the port wiped completely cleaned, no carbon stuck to the walls. Could not wipe any other exhaust ports clean of carbon with a rag, not even a rag soaked in solvent.

I used solvent to clean the #3 combustion chamber and then magnafluxed it and the exhaust port, no cracks. The exhaust valves for #3 are going to have to be replaced so I will check it again for cracks when the valves are out as it is difficult to see around the valve head even with the cam holding the valves fully open.

I am seriously thinking of just getting a new head, maybe a reman head because as I was cleaning the exhaust port, I did not like the feel of one of the walls, It did not show a crack, but it did not feel right either. Possibly it has a porosity issue, which is a casting defect that would have been with the engine from the beginning, but it never used any coolant before now. BTW, it has 121k miles on it.

I should add that the entire port and faces of the valves showed a coating of the sealant, but there was one large and two or three small volcanos of the sealant in the port. Large being over 1/4" tall and 1/2" diameter, the small ones about half that size.

Also I did find a small scratch in the #2 cylinder liner at the top. The dye did not penetrate into it, it is only on the surface and a closer look at the head gasket shows that coolant could have breached at this point, but in to the #2 cylinder only.

Don’t entirely dismiss unintended consequences of the prior disconnection of the oem mini-radiator. While the mini-radiator itself may not be needed in revised CAI configuration, there may be a coolant path through it and the engine/cylinder head that still needs to be kept open. .

Upon further examination, it appears that while running, coolant got into all cylinders. The head gasket fixer then crystalized in all the exhaust ports and coated all the valve faces. It hardened on the valve faces. That cr@p did a lot of damage.

Did the easy thing, ordered a new head. Cost vs time seemed like the best option. Going with a Cometic gasket and ARP studs and an internal block brace.

What is your current theory about how coolant was getting into the cylinders?

Head gasket. The coating they use simply eroded away. It is a problem with open deck designs common today, like Nissan and Subaru.

The car is a Sentra Spec-V and it has the same engine as used in the Altima, but with a manual transmission in a vehicle that emphasizes performance, and this car has been on the track a few times, they have a history of blowing at about the 100k mark.

This engine went to torque-to-yield head bolts starting in 2007 and that helped stop the head gasket issue. Some 2006 engines also got those bolts, but not this one. Also this was one of those cars that Nissan sent the short blocks back to the factory for reman because of the oil control rings so the head was replaced at a dealership, not done in a factory. That could also be a contributor.

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