Coolant Leak on rear upper passenger side, cant even see it!

[CanuckQx4]

hey guys, big problemo happened today while I was at the store.

I was inside my little auto store picking up a part for my other car, left the car running since I was supposed to just grab and go, well I ended up waiting 20 min, left the car running (ended up forgetting damnit) and one of the clerks eventually saw my car smoking so i ran out, seen a HUGE HUGE HUGE ploom of smoke coming from the engine, I honestly thought it was on fire as I was running over until I seen the huge coolant leak.

I took the keys out, took note that the temp gauge was still under half. Popped the hood and the whole engine was coolant sprayed. Noticed that the top of my 3 year old ebay radiator had POPPED IN HALF!! The whole top section seperated from the core. I started filling it with water and could hear it leaking out the back of the engine near the middle of the car. Towed it home, wasnt going anywhere. I did check both the oil and trans fluid, both looked good so I dont believe it got to the point of headgasket failure.

Just had the front end up on jackstands, and when pouring water into the rad to try and see where it was leaking from, it is very difficult to see, but the start point I could see the water was rolling off of the surface where the head meets the block, the block is a little wider at that point so all I can see from the bottom is a little waterfall. Not sure where its originating from.

Any pointers for me here guys? Ive had the plenums off to do the power valve screws, but this leak almost seems below that point, and possibly maybe even unreachable in my driveway, so cramped between the firewall and engine, work seems very difficult if possible, most likely blind. What would be leaking?

I orderred a rad and it should be at the parts store in the AM, but Im wonderring where to go from here.

[CanuckQx4]

I think I dodged a bullet and the crossover pipe may still be good

Definetely the biggest job Ive tackled on this truck to date. After near a full case of beer and having to use a step stool to do half of the work. I managed to get all 3 sections of the intake manifold off, and the fuel rail, and all the little bits and pieces that go along with it. Presume I found the leak, hopefully its the only one down here!! Look at the burst! I didnt touch it before this pic



So now Im trying to figure out all the parts I should replace to reassemble, and fix while Im down here. And I believe Ive heard there is a second thermostat? Also a water control valve. Should either be replaced?

Does anyone know where the back thermostat is? This hose that popped was connected 2 housings that in my head both could be a thermostat, but I dont want to crack them open and destroy the seal on something I shouldnt and make life harder. Anyone know if its the one on the crossover pipe or the one on the engine.

And incase anyone was wonderring what the VQ looks like with all the manifolds and fuel rail and such off. Here it is



You can see the 2 shiny water necks at the back where this burst hose used to be.

[Slumpert]

Nice job

[Chuck Tribolet]

That's a hose I didn't know was there.

FSM only shows one thermostat, but it does show a "water control valve" and it's right where you are. I think it's the elbow at the right side of your picture of the burst hose. See FSM, page LC-18 on the 01 PF FSM, about the same in your QX-4 FSM.

MMM, the test procedure for the water control valve indicates that it IS a second thermostat.

Chuck

[Chuck Tribolet]

Rereading your original post, I think you some sort of high pressure event in the cooling system. I'd get a new rad cap on general principles.

How many miles on your truck?

Chuck

[CanuckQx4]

The new radiator did come with a new cap aswell. Still waiting for Nissan parts dept to call me to say the hose/pcv/gromet/gaskets are in so I can put this back together.

Truck has 125k miles

What page is a test for the water control valve? Id like to test it if I can before reassembling

[Towncivilian]

LC-18

[CanuckQx4]

Thanks town, think I should open up that water neck and test it?

At this point Im not sure what caused the failure, just that the hose burst, could have just been old, but Id hate to put this all back together tomorrow/saturday to find that valve somehow failed closed. I think I read somehwere that they always fail open though...

[Chuck Tribolet]

Assuming the water control valve works like a normal car thermostat, which it looks like it does, it's pushed open by a wax pellet, which would fail closed if the wax leaked out, any old setting if corrosion caused it to stick.

The test procedure is page LC-19 in my '01 PF FSM. It's the very last thing in the Water Control valve section.

I'm surprised the water control valve didn't come up when I was having overheat problems a few years ago.

Chuck

[CanuckQx4]

The coolant is mixing with the oil, headgaskets must be toast

Not sure if I should try and fix this engine or simply find a replacement to drop in. Just spent to much on a new transmission, tires and rad to call it a day on this truck.

Headgaskets are going to be a huge job alone though

[Slumpert]

Sorry to hear about this. In my opinion to do the repair correct your gonna need to pull the engine and have the block and heads milled.

[Chuck Tribolet]

I think I'd pull the heads and check the top of the block. Often it's just the heads that warp.

Chuck

[CanuckQx4]

Going to be a huge job if I decide to try it

[CanuckQx4]

Can you guys think of any hoses I may have simply switched. Possibly having a PCV/vacuum hose swapped with a coolant connection.... maybe that could cause the engine to be fillling with coolant as I fill the rad... Looking at the engine I dont see anywhere I could have made the mistake.

I also dont think any of the intake manifolds i just took off had any coolant passages, where if maybe I didnt get a good seal putting them all back together, coolant could be leaking in.

You guys know these VQ engines pretty well, can you think of a spot I may have swapped the incorrect hoses?

[Slumpert]

I am unsure of your questions. If you managed to switch a vacuum hose with a coolant hose you would not have gotten 2 months of driving done.

It is certianly possible that you have had a head gasket leak for these two months though.. Maybe think back to the circumstances that lead to the new radiator.. Did it over heat then?

[CanuckQx4]

2 months? I meant I thought it may be possible I switched the hoses at the same time I replaced the radiator and the hidden coolant hose under the intake manifolds just a few days ago. I figured I may have made a mistake when putting all of the intake manifolds back on (there are 3 intake manifolds)

Its probably not a switched hose, and the headgaskets probably just blew when the radiator and hidden hose exploded. Im just trying to rule out a mixed up hose I suppose

[Slumpert]

I missed the whole part that you already assembled everything back and now had coolant dumping into the oil.

If your leaking that much coolant you likely could take out all your spark plugs and do a compression test.

Dont skip taking all plugs out as you might have a flooded piston.

[CanuckQx4]

So you think I could pinpoint a cylinder by doing a compression test? Ive never had a blown headgasket before

I do have a tester and could pull the plugs I guess and be sure there is no flooding somehow creative. I'll see if i can get it quickly moved under cover of the garage

[Buzzman]

Just thinking about this gave me an idea: You might be able to pinpoint the leaky cylinder(s) just by checking the condition of the spark plugs.

On the other hand, as I'm typing this, it also occurs to me that a blown head gasket doesn't necessarily mean the coolant is now going into the combustion chamber.
Some head gaskets blow outwards as opposed to inwards. Oh well.

Check the plugs either way. It may help to isolate the leak.
It would be less work if you only had to pull one head, and not both.
Good luck.