VQ w/ possible blown headgaskets, how to be sure.

[CanuckQx4]

And the rear water control valve in the back, that failing would not cause coolant to find its way into the crankcase right? You just mean I should replace it, not that it could be the cause is what im reading

[Slumpert]

At mininmum your looking at replacing a head. Might be replacing the block.. labor vs cost might go towards just replacing the engine.

Sorry for your situation, but kodos for doing that much work to try to figure it out.

[Slumpert]

I suppose it is still very slightly possible it is a head gasket blown out internally.. ie not on the cyclinder side.

[CanuckQx4]

Gotta keep the fingers crossed I suppose. I orderred a new oem water pump today, might not arrive til Monday, so I will sit and wait

I dont have $3-4000 for a new engine/install, so it would sit for quite some time if that was the case. Wish the headgaskets were a DIY job and the engine didnt have to come out!

[CanuckQx4]

Well since im inpatient and I wanted to pull the rear water control valve, I had to pull all 3 pieces of the intake manifold again, fuel rail and injectors. Alot easier this time with the air ratchet. I pulled the rear water control valve and plan on boiling it to check operation for the hell of it and replacing it.

Again under the valve was perfectly clean green fresh coolant. Why is there no oil mixing into the coolant, if the coolant can mix with the oil without the engine even running, why has the oil never made it into the coolant?

Maybe that points to a certain area?

It gave me a very good look at the intake valves aswell which I took a good look at and they were all dry

[CanuckQx4]

Might have found my smoking gun as to WHY the truck overheated in the first place. As I said I pulled the rear water control valve earlier, which is a primary "thermostat" in the vq35 engine. I noticed it a few minutes ago when I was inspecting it that it was not sealing at room temperature tightly, and when I put it in water and slowly boiled it to 105* celcius (rated for 95*) it didnt budge a bit. Its seized.

The water control valve also happens to be just inches from the hose that burst on me a month ago when this whole fiasco started. Its on the right under the neck. *this pic is from a month ago, before I replaced the hose and radiator*





Any surprise reasons on how coolant would be going in the oil but oil not in the coolant?

[4xq]

Yep, sounds like that is the part that caused the problem.


As to water in the oil only: It depends on what breaks, and where.

Once you have confirmed the water pump is not the problem ( there is a seal on the shaft behind the impeller so to be 100 % sure you can replace it to be positive) then you have:

1. Broken a water jacket around a cylinder down in the crankcase and so it is draing coolant down into the oil from there. (Bad block)

2. Broken a water jacket in the head. There are passages in the head for oil to drain from the valves and cams back down into the crankcase, and coolant is draining from the crack down that drain passage into the crankcase.

3. A busted head gasket letting coolant move from a water jacket across to one of the drain passages in the head.

If you were to get a crack between an oil pump passage in the head and a water cooling jacket in the head, you would start getting oil in your coolant because oil pressure is higher than coolant pressure. It pumps oil into the coolant.


If you end up having to pull the engine, you can rent an engine hoist. You would want to find a used engine either on car-part.com, or by calling junkyards. I don't know what used engine prices are like in your area, but you can get a complete used engine here for 750.00 to 900.00 U.S. with a 90 day warranty.

[CanuckQx4]

Well the only reason I dont believe its my water pump anymore is because I was not leaking out of the weep hole and I confirmed the weep hole wasnt plugged. So if that oring were to have been bad, it would have leaked out the weep, and not mixed with the oil right?

None the less I already orderred the pump, if it doesnt stop the mixing I could easily put it on a used engine

A used engine goes about $1250 -1500 in canada, but with the track record of VQ's burning oil and eating power valves, I almost want to repair my engine since I know it does neither (but it does have 130k)....

[4xq]

Yes, the chances of the pump being bad are slim. I just don't want to say tear down the engine and then have you find out its the water pump.

You are also correct about the head gasket not typically leaking that fast.

As Slumpert said, you are probably looking at a bad head or bad block. When that coolant finally boils, the steam creates tremendous pressure. Sometimes the soft parts that fail ( your hose and plastic radiator top) just can't stop the big damage.

[CanuckQx4]

Ya the way it guzzles the coolant and the perfect compression are the only thing that have me holding my breath it may not be headgaskets. But now seeing this water control valve siezed up about 1/16" open, Id imagine it got pretty hot.

And seeing that weep hole not be clogged, I dont see how coolant would make it to the oil in there, unless I dont understand and only the one oring needs to blow and coolant can go someone other than the weep hole....

I sent out a few feeler emails to semi-local engine places.

[Slumpert]

Well since you got all that off. Fill up the coolant system and see if it stays stable or leaks out. If you can fill it up to that rear thermostat and it does not leak into the oil then you know the leak is HIGHER. Which would put it in a cyclnder head

[CanuckQx4]

If I had a waterpump to throw in I would do that, nissan hasnt called me today though so it looks like it may have to be monday

I did however get a very good quote of $2200 for a jdm vq35 with 60-90k installed with 90 day warranty. All the other quotes were $3300+

[CanuckQx4]

put the water pump in, still drinking water into the crankcase, I listenned hard for it to while filling, I would pause and its definetely "glugging" from the passenger bank

Oh well, time for a new engine. Wish I didnt like this truck so much Id kick it to the curb

[Buzzman]

Just gotta say, I've been following your thread with great interest.
Sorry I can't really contribute anything, but please keep us up to date as you go through this mess.
Thanks,
Another Canuck (Ottawa).

[robbykennedy]

put the water pump in, still drinking water into the crankcase, I listenned hard for it to while filling, I would pause and its definetely "glugging" from the passenger bank

Oh well, time for a new engine. Wish I didnt like this truck so much Id kick it to the curb

It might also be a blown water seal, the water seals are made out of bronze when they overheat they tend to leak.

[AirdrieQX4]

CanuckQx4,

Having a similar problem with my 99 QX4. Also overheated with steam coming out from under the hood when my wife was driving it close to home. Filled up the rad to drive it home < 1km and parked it in the winter, with lots of fluid dripping down that I collected in a bucket. Starting to warm up now in AB so can take a closer look at it outside. Had a small water pump leak and intake gasket leak before the overheating and now also suspecting a head gasket problem but I need to see where all that fluid is coming out. Have other vehicles to drive so just getting around to it now.

What part of the country are you in and what kind of garage gave you the best estimate for the new engine, just in case I need to go that way?

[CanuckQx4]

What the heck is a water seal? I'll google that obviously in the next minute, but how would that cause the coolant to go straight into the crankcase after adding a few liters??

[CanuckQx4]

What about the oil cooler guys, could that be causing the milkshake?

[Towncivilian]

The Courtesy Parts exploded parts diagram is more detailed than the FSM: http://www.courtesyparts.com/pathfinder ... _4729.html

It's hard to say whether there's some internal seal. Maybe that rubber O-ring (21304)?
I don't know how one would bypass the oil cooler easily. It seems there's a bracket for the manual trans equipped R50s but that looks like a lot of work to install that plate for a few miles to see whether coolant entry continues.

So to overview, at this point you've replaced:
Water pump
Primary thermostat
Water control valve

Correct?

[CanuckQx4]

yes correct, and my 21304 O-ring is new within the last year

[Leo1998]

Check your "expansion" or "freeze" plugs on the cylinder heads and the block to see if any have failed.

Sounds the same as yours, read all the posts: http://forum.ih8mud.com/threads/oil-pan ... or.486123/

[CanuckQx4]

There are no external plugs leaking, but I wasnt aware there were possibly internal freeze plugs.. Does anyone know if we do?

[CanuckQx4]

Is anyone familiar with freeze plugs at all the on VQ? I cant find anything on them at all in the fsm, tried all the names I could think of, theres gotta be freeze plugs on the engine, but are there internal one or ones that could cause coolant to make its way into the oil

[CanuckQx4]

Anybody?

I looped the oil cooler coolant lines today just to rule out the oil cooler possibly failed internally, to no luck unfortunately, my last hope is the possibility of an internal frost plug, can anyone confirm or deny there existance and WHERE they are on the engine.

It makes sence to my problem if there are infact internal plugs

[Towncivilian]

I have never read anything about frost plugs in our VQ35DE engines.

Bypass the throttle body cooling lines and see what happens. Maybe the IM is leaking and causing coolant entry.

[CanuckQx4]

I was told there is no coolant passing through the intake manifolds though..? wrong?

I will bypass after work

[Towncivilian]

Perhaps I was mistaken - LC-10 shows the coolant only entering the throttle chamber. Still, the lines are fairly easy to bypass, so give it a try anyway.

[Buzzman]

I was told there is no coolant passing through the intake manifolds though..? wrong?

LC-10 shows the coolant only entering the throttle chamber.

After having replaced my IACV and having the throttle assembly apart, I can verify 100% that the coolant only runs through the throttle body.
I also had the intake manifold off last year when checking the power valve screws, and there is no coolant running through there.

[Leo1998]

http://www.youtube.com/watch?v=kzr2mEYDjko and this one too http://www.focusfanatics.com/forum/show ... p?t=284552

Read comments...It talks about a product called Steel Seal fixing the "plug" leak under the valve cover. I guess it's a plug that has a torx head on it.

I think you are going to have to put fluid in your radiator to really diagnose the problem and eliminate others. Also to find out what cylinder has fluid in it.

Here is a video on how to use Steel Seal, people say it will take care of those plug leaks. http://www.youtube.com/watch?v=YL9QjN7AcW8

Here is a VQ35DE head...You can see the plug. http://www.nwpengineering.com/forum/VQ3 ... embled.jpg

[CanuckQx4]

You are giving me hope LEO!! I have suspected all along (but I thought I was being stupid) that my problem cant be a headgasket failure, the water just flows to fast right into the oil crankcrase when Im filling the radiator with coolant.

Is this the plug you are refering to? the internals of the head look different than any head Ive seen, Id assume it would be littered with cams/parts inside if I were to simply remove my valvecover and try and get access to that plug?



The Stop Seal does sound like a decent product, but it relies on your cooling system to be able to hold coolant and have the engine run enough time for it to set, my coolant goes into the oil to fast to be able to run the car, but this gives me hope I may be able to seal that plug myself.

Any idea how accessible it may be if I were to take the valve cover off?