VG33E head gasket failures and head warp

Yeah, I ran across this article on the VG30DETT engine that calls out major casting issues with that block, causing overheating of the rear cylinders (this is where I see the HG's failing). http://www.motoiq.com/MagazineArticl…TT-part-1.aspx

There are a couple cool photos of the coolant passages being blocked from the factory, and what they look like once the block is ported. I didn't look that closely at my blocks. I'll take a look at them today. I wonder if they have the same issue as the VG30 block.

As a master tech at a Nissan dealership, the biggest issues I see that left unrepaired causing head gasket failure on the VG33 are;
-corroded and leaking thermostat bypass hose
-corroded and leaking lower plenum gaskets
-stuck closed thermostat
-ruptured radiator top section (plastic part)
-cracked exhaust manifolds which lead to restricted catalytic converters

Other ares of common coolant leakage are the thermo-element below the throttle body, sealing surface between the lower plenum and upper coolant outlet neck, and the heater hose/pipe connections.

You will be surprised at the number of people who ignore perceived "minor" coolant leaks because the temperature gauge never reads hot. Truth is the coolant temp sending unit is located near the highest point in the cooling system, and when a small loss of coolant happens it causes the sending unit to not come in contact with coolant. With no proper contact with coolant the sending unit sends erroneous readings often indicating normal temps.

Oiling issue aside, there should be no issue with lubrication outside of extreme circumstances.

and i agree 'Yotas have a tech edge on Nissans - but as for tried and true Nissan is the Ford of Japan, they just work not as efficient or powerful but they chug along

proof is in the pudding, these engines mate anode and cathode metals, corrosion is a major peeve here. I've flushed the system twice from 60k and 90K, will likely do another this summer - favoring on a 70/30

and yeah, i snapped that shitty little nipple on the upper cap.. shitty design, the epoxy is holding up so far

passenger manifold #1 cracked cats clogged to shit, dropped in doug thorley headers and air gap pipes

Wow, interesting perspective…
In your experience, how do those smaller coolant leaks point toward evidence of the HG failure issue? Do you mean the small coolant leaks are enough to disrupt the coolant flow in the system, even while under pressure, enough to "miss" the coolant temp sensor? Wow. That's bad design.

My shop truck (old 88 Toyota pickup with that pesky little troublesome V6), leaks coolant and oil out of it so much, it requires a weekly refill, AND it has a known design flaw in the HG area (that Toyota addressed properly and actually "resolved" it in the recall), but that engine doesn't seem to have the same re-occurrence issue as the Nissan VG family of engines.

Good to know about lubrication. I was hoping to I could resuse my oil pumps, but was starting to worry about all these problems racking up.


Interesting about your coolant ratio choice. Do you have any indication that this is helping? I'd really like to monitor the coolant temp or the combustion temp in the two rear cylinders (#5, #6). Right now, the best evidence I see, point toward block manufacturing flaws. I looked at two of my VG33E blocks, and both have the same casting flash issue as the VG30 used in the MotoIQ article referenced above. I took the blocks to three machine shops yesterday for opinions…

The first shop, a mostly domestic shop, said that it didn't look "that" bad and wouldn't "worry" about it (this is the same shop that milled by heads .010", further than recommended by Nissan, and told me "not to worry about it". I find that hilarious! They have no experience with a motor after it has left their workbench.

The second shop, who's owner repaired an Xterra for his daughter recently, after trouble with the HG's, said "You're probably on to something…let's drill that out of there!" I elected not to do it, but would rather practice on one of my blocks with a hole in it already (threw a rod).

The third shop, frowned and agreed that the manufacturers don't care about this kind of issue and suspected it certainly wasn't good. He showed me the tool that he would use to grind it out by hand (like a air die grinder with a 12" long shaft and a bit on the end of it).

It's hard to say, without knowing the exact path of the coolant in the block, but by the looks of it, if coolant is supposed to travel down that center channel all the way to the back of the block, this is likely a contributing factor, if not root cause. It's probably the best mod I could consider doing, to address the issue. So far, nobody has added their HG failure info to my registry thread on clubxterra.com, but all my HG failures, so far, are in cylinders #5 and #6. Coincidence??

I am talking about the coolant leaks being minor, but over a long period of time. Owners never realized it got hot because the gauge said it was normal. Basically you get air pockets in the heads when coolant gets low and creates extreme hot spots.

I am in the process of replacing head gaskets at work on a 02 Xterra because the lower intake manifold gasket was leaking around the port for number 5 and guy never paid attention until it suddenly started smoking white clouds out of tail pipe. The amount of green dried crusty coolant built up around spark plug #5 and the valley around the knock sensor is insane. That tells me it was a long drawn out leak that went unnoticed.

i'd tell ya throw a head kit on it and see what happens, rockauto has some on wholesale now - join their mailing list and you will receive wholesale notices. Victor Reinz/Beck Arnly is OEM quality so look for them.

Not wanting to get too in detail, keep clean and prep your surfaces.

70/30 coolant is to favor corrosion prevention, and holds temp fine.

Don't trust MotoIQ, they're nothing but a car bro photoing their friends build going on heresy. Let alone, you're comparing a DE to an E. Adding to that the E series has seen major casting series variations, unless they site casting references/serial numbers… take it with a grain of salt,the E series has nearly 5 or more variations..

Sort of off topic but on Nissan quality, once I got to know both the single and twin cam VG's they were disappointing to me, particularly in design. The crank support could have been a lot better, X bolting would have been justified particularly the turbo's. The single cam's complete intake design restricts power and it's virtually impossible to fix all of it without a complete redesign like was done by Nissan for racing. Funny thing is the RB30, other than the problem previously mentioned, is superior to the VG for general use and has far better breathing potential. It's all about design which does not necessarily cost more.

Ok, yeah I understand there are leaks, several, and slow, but I guess what I'm getting at is…what about the leaks is direct evidence of the HG failure? I always look at these issues like a murder investigation, and each sign or symptom is a piece of evidence. I would agree the leaks are evidence, but I don't yet see them as a smoking gun. I will admit, I haven't studied the cooling system entirely, and you could be right, but it just seems to me that you would have to have lost a lot of coolant for the entire system to loose enough pressure to create large enough hot spots to cause failure of the HG's…especially at 40,000 miles. Some of the failures reported are that early.

The defects in the primary water channel of the block, is (so far) the most logical potential source of root cause to me. It would certainly lend credit to the idea the back two cylinders are not getting proper cooling. It might be hard to determine, without adding some temp sensors, but I could imagine the back of the block and heads getting extra toasty without proper flow from the primary channel. Again, I haven't studied the entire water flow design yet, but this block is known to have multiple other issues near the back of the engine. That pesky knock sensor…nobody seems to have solved that problem either. Why does that go bad? Could be long term heat failure. ??

It seems to me the problem is likely more global that the little water leaks, but I could be wrong. Having said that, the overall cooling design with the manifolds, thermostat and temp sensor location, etc., etc. are almost ridiculous. I had the two stupid plastic nipple crack on the heater core. What fun that is!

Uhmmmm..NO. I don't want to just throw on a head kit on and see what happens. That's the reason why the problem reoccurs and repeats over and over. This issue requires attention. Attention that Nissan SHOULD have put to it. There is a problem here (and a potential solution), but we must find it.

If I'm going to stick lipstick on a pig, it's going to be pretty…
1 - HEAD GASKETS: I've already had to over-mill the heads (according to Nissan spec) and I need to consider a solution. I'm talking with ASCO to produce a thicker MLS HG for me, based on the .010" I lost on the head surface. The overall cost of MLS gets sucky, since I may have to surface the decks of the block to meet sealing requirements of the HG manufacturer. I was considering renting a profilometer to measure the stock block surface, to see if it happens to meet the requirements already (Ra <= 50). This is a costly rental too.

There is also an option to use a thin aluminum "shim" offered by Innovative Machine & Supply. They are a minimum of .020" and require Hylomar to seal the shim to the head and block. I've never used a solution like that, so I don't know what level of confidence to expect.

I could be getting super picky now, but my confidence is dwindling and I simply don't want to add to the number of uncertainties already present. I'm less concerned with overall combustion chamber volume loss, but combine that with spark and valve timing variances and I'm introducing more variables to the outcome. Perhaps I could simply choose an adjustable cam gear to work out the difference in timing due to a reduced thickness of the heads.

2 - BEARINGS: The main and rod bearings are shot in the bottom end, likely because the PO drove the vehicle a few times with coolant in the oil (I removed over 6 quarts of total volume from the oil pan when I drained it (that can't be good on oil pressure). Nissan doesn't sell the bearings anymore, so I have to buy a "one size fits all" set of bearings, and either deal with the bearing clearances being in various levels of the tolerances, OR spend the money and have the crank turned to match the bearings.

3 - HEAD STUDS: ARP head studs (super costly) could be considered, or slightly over-torquing the OEM head bolts a little bit. That's an ugly solution, but it could "add" to the solution if I'm going to stack up band-aids anyway.

All in all, I think I'm best suited to continue to look at a more global solution, rather than all the band-aids. I can't believe people experience these failures over and over, and the vehicles are sold and bought by new people who continue to throw money into repair shops putting more lipstick on this pig. I'm into this far enough, I might as well port out the block and give that a go with everything else back to spec. Problem is, I might have to drive it a long time to verify if it have solved the problem. Or, install some custom temp sensors near the two rear cylinders and monitor the temps. I would have to do this on two vehicles though…one that is completely stock, and one with the block ported.

I hear ya. I'm a bit surprised too. I've been working with the 3SGTE engine from Toyota for many years, and have just become used to it's excellent design and superior reliability. This is my first V6 engine though, so I'm learning the design requirements for intake manifolds, etc., are much different from the simplicity of the inline cylinder designs. Is there any aftermarket solution for an intake manifold for the VG engines? Upper or lower?

I think you are over thinking the whole situation. After fixing the leaks/thermostat and replacing the head gaskets and resurfacing heads as needed we have yet to see the same vehicle blow head gaskets again.

Yes, but that could be for various reasons…perhaps they no longer own the vehicle. Perhaps they have moved. It's probably not enough information to suggest the problem doesn't repeat, but you could be right. If you look at clubxterra.org, there is evidence people are experiencing multiple HG failures. People are heart-broken. These vehicles end up being a throw-away vehicle. They don't sell at auctions for more than a few hundred bucks, according to my used dealer friends. I'm trying to find a better way to keep them on the road. The service to replace the HG's at your dealership must be approaching or exceeding $4K now-a-days. The only way I can see is to buy them, find the correct solution to repair them, and re-sell them for a reasonable price that doesn't require a $140/hr dealer service price tag.

You have to take your observations on clubxterra with a grain of salt. The vast majority of SUV owners are extremely mechanically or maintenance incompetent. Same holds true for just about any group of auto owners. Yes they may be savvy about their vehicle, but lack big time in maintaining their vehicle. And by maintaining I mean more than just regular oil changes and actually fixing things as they go bad under hood instead of waiting and waiting until something drastic happens like a head gasket going bad.
Another prime example I use are your typical Z32 owner. That is why you see so many Z32 going for dirt cheap with a massive bill of repairs waiting for the next owner. There are a few owners who actually spend money to fix them but those are a small fraction of the owners.

At our dealership we have a guy with a 02 Frontier SC 4x4 5-speed with 336k miles. Never had a head gasket issue. He promptly fixed all the minor coolant leaks and such that I mentioned in my previous post. He has even had to replace the super charger twice now, but the engine bay looks almost as clean as the day it left the factory. It's all about staying on top of repairs.

ether overthinking it or you have a shot ass motor

the vehicles, and chassis that run the engine/trans combo that are related are pushing 20yrs at best from their latest revision. NOW they are seen as throw away USA side but they are built to last with scheduled maintenance, don't fight the truth. Just this weekend i found a leaky trans cooler line clamp on the D22 S/C during a fluid change/check, and the VG33ET Z collapsed a lifter after a hard run from sitting 2mo just to come back after a soft cruise. It's old technology and requires a bit more of a specific ear. This isn't read a code type shit bro.