Coolant leak

[makie]

A little over a month ago I changed my timing belt, water pump and thermostat. Two weeks after that I developed a coolant leak and initially I thought it was the water pump gasket on the top right (passenger) side. A PIA but not a big deal to go back and fix. But I've been watching it because I wasn't totally sure where it was coming from and now I'm fairly certain it's not the water pump. It seems to be coming from a small metal tube below and behind the thermostat housing. Coolant appears to be leaking from back there and then running forward and down the water pump (which is why I initially thought it was the water pump).

 

So my question is, what's back there and can it even leak coolant?

 

thanks

[Kingman]

Coolant bypass hose. The one that feeds the thermostat and is right behind the rear timing belt cover.

[Slick]

^^^ upper radiator bypass hose (official name) here's a pic of my engine with a good view of the bypass hose. it's a $5 hose, PITA to change. When you DO change it, also change the clamps to the type I have on mine.. much easier to tighten when the engine is complete.

If you get the hose from anyone other than Nissan (I got mine from Kragen), you may have to trim the hose a little, they are not an exact fit.

 

 

Edited May 16, 2011 by Slick

[makie]

Thanks for the help folks! After I posted this I did more searching in the forums and came across threads about the bypass hose so thinking that was the issue I went and bought a thin wand light that I could stick back in there to have a look... unfortunately I don't think it's the bypass hose, but I wish it was. I'm pretty sure it's leaking from the very back of the thermostat housing, back and below the intake manifold.

 

It's really hard to see back there though, I can only see one bolt but the area definitely looks like a leak is happening there. What does this attach to? Is it part of the heating circuit?

 

And the question I'm afraid to ask, how on earth do you get to it? The one bolt I can see is facing backwards so even if I take the cam pulleys and rear timing cover off I still don't think I can get to it. Does this require taking the whole intake manifold off?

[Slick]

Thanks for the help folks! After I posted this I did more searching in the forums and came across threads about the bypass hose so thinking that was the issue I went and bought a thin wand light that I could stick back in there to have a look... unfortunately I don't think it's the bypass hose, but I wish it was. I'm pretty sure it's leaking from the very back of the thermostat housing, back and below the intake manifold.

 

It's really hard to see back there though, I can only see one bolt but the area definitely looks like a leak is happening there. What does this attach to? Is it part of the heating circuit?

 

And the question I'm afraid to ask, how on earth do you get to it? The one bolt I can see is facing backwards so even if I take the cam pulleys and rear timing cover off I still don't think I can get to it. Does this require taking the whole intake manifold off?

what part are you trying to remove? the t'stat housing? the URBH can be done engine complete, if you changed the h2o pump you know what's involved there. did you change the gasket to the housing? use gasket sealer?

pull the intake off so you can get a better look back there, when the hose leaks it is deceiving as to what you think is leaking. You can unbolt the intake and just lean it back (carefully) to get a look without unhooking everything.

if you are wanting to get to the t'stat housing you will have to remove cam covers.

Edited May 16, 2011 by Slick

[makie]

When I changed the water pump I used a gasket and rtv, for the t'stat I only used rtv.

 

At this point I'm about 90% sure the leak is from the backside of the t'stat housing where it attaches to the block (at least I think it's the block). The spot, which I'm not explaining very well, is in the same plane (front to back and side to side)as the where the return pipe (the one with the temp sensor in it) mates to the intake manifold but about 4 inches lower.

 

When my wife gets home with the truck I think I'll be able to see coolant bubbling out from there to confirm.

 

So Slick I'm guessing the whole t'stat housing has to come off but the bolt heads face backwards so I'm concerned that even with the cam covers off I wont be able to get at it. Let me ask this, with your engine (which has given me engine envy by the way) in the state it's in in the picture would you be able to get the t'stat housing off of it? Or would the intake manifold have to come off first?

 

thanks again.

[adamzan]

Where in canada are you? Maybe someone in the area could stop by and lend a hand.

[makie]

If I'm in Ottawa are you offering?

 

You're off the hook, I'm just a little drive away in Victoria, BC.

[makie]

I just want to clarify something that might be causing some confusion. I noticed the Haynes manual calls the t'stat cover the housing but when I said housing I was referring to the part the t'stat actually sits in, not the cover that holds it in place. The leak isn't coming from where the cover mates but rather from a joint at the very back of the whole t'stat assembly.

[Kingman]

There are three soft plugs in the valley of the block, and a metal hard line that mates to the back of the thermostat housing. That's all there is behind the thermostat that could leak. To access them the lower intake manifold will need to be removed.

Edited May 16, 2011 by Kingman

[makie]

OK thanks, I think that's what I needed to know.

 

I'll go through the how to's to find info on removing the manifold but is there anything i should know before starting it? Is it something I should even attempt? I was ok with changing the timing belt so that's about the the skill level I'm comfortable working at.

 

Anything else I should replace while I'm in there?

[Kingman]

It's relatively easy. But be prepared to purchase new lower intake manifold gaskets if needed. The factory ones are metal with rubber o-rings to seal the intake ports on the head. They usually aren't bad and are re-usable, but re-using ones in poor condition is a recipe for failure and another tear down.

[Slick]

OK thanks, I think that's what I needed to know.

 

I'll go through the how to's to find info on removing the manifold but is there anything i should know before starting it? Is it something I should even attempt? I was ok with changing the timing belt so that's about the the skill level I'm comfortable working at.

 

Anything else I should replace while I'm in there?

It's relatively easy. But be prepared to purchase new lower intake manifold gaskets if needed. The factory ones are metal with rubber o-rings to seal the intake ports on the head. They usually aren't bad and are re-usable, but re-using ones in poor condition is a recipe for failure and another tear down.

what James said, and you will also need an alan head socket for the intake bolts, i have the size, i just can't damn well find it at this moment in time. I have 2 write ups about coolant leaks/tear downs (maybe even 3)...

i am still confused as to you saying the bolts are "backwards"...... there is no humanly possible way to install the bolts from the back.. unless i'm reading it wrong.

you will also need a gasket for the t-stat housing, just using rtv is not enough for that.

Napa auto parts sell a nice, good quality intake gasket that i use, they are $6 and i've never had an issue with them. you can get the h2o housing gasket anywhere.

if you changed a timing belt, you'll be more than fine doing this job, and we're here if you need us.

[makie]

I think it's me, I'm not explaining it very well. What I believe is leaking is the metal hard line that Kingman referred to. The head of the bolts that go through the flange on that hard line face the back of the truck. Or so I think, it's REALLY hard to see anything back there. So i didn't mean to imply they were in backwards, just facing the back. Any better?

 

It's a long weekend coming up so I'll pick up gaskets this week and hopefully get this solved. Slick, I haven't been able to find your write ups, if you have the links I'd appreciate it!

[Slick]

I think it's me, I'm not explaining it very well. What I believe is leaking is the metal hard line that Kingman referred to. The head of the bolts that go through the flange on that hard line face the back of the truck. Or so I think, it's REALLY hard to see anything back there. So i didn't mean to imply they were in backwards, just facing the back. Any better?

 

It's a long weekend coming up so I'll pick up gaskets this week and hopefully get this solved. Slick, I haven't been able to find your write ups, if you have the links I'd appreciate it!

ooooooooooh, ooooooooooooooK lol i was trying to get the visual lol

 

here's a few of my write ups from waaaaaay back when....

 

coolant loss

 

head gasket

 

also head gasket

 

bypass hose

[Kingman]

Here are a few pics of the coolant hard line that runs underneath the lower intake manifold.

 

 

Here's a little lesson I learned the hard way because I didn't slow down and take my time to think. This is the first time I've messed this up and will definitely be the last. Coolant runs through the lower intake manifold, and down in to the block next to the cylinder intake ports. Not draining the coolant before removing the lower intake manifold will result in cylinders full of water and a massive mess as you can see from the pictures.