Jump to content
colinnwn

Installing oil catch can on VQ, and bypassing throttle body coolant lines

Recommended Posts

 

I'm trying to see where the PCV line comes into the bottom of the throttle body from the passenger side valve cover. I don't see anything related to that. I do see the 2 hoses for the coolant that flows through the throttle body. Does anyone know what the size of hose those are, so I can order a pipe nipple to bypass it as I do the rest of this project?

 

Does anyone have some pictures of where the PCV hose comes into the throttle body? All I see is the ventilation hose from the driver's side valve cover to the rubber intake boot. The only thread I found google searching for pics goes to another Nissan forum where all the pics are no longer linked. I'm afraid I'm going to have to start taking things apart to find it, and I'm worried I won't have everything and will get stuck waiting on parts.

 

Thanks

 

 

  • Like 1

Share this post


Link to post
Share on other sites

1/4 inch hose fitting to bypass that. And I believe the hose from the pcv plumbs right into the air intake elbow before the throttle body 

Share this post


Link to post
Share on other sites

Thanks. If it goes right into the plastic air intake elbow, then on my 2001 VQ it must come off the drivers side valve cover. I have about a half inch by 12 inch preformed hose that does an L into the intake elbow.

Sent from my SM-N950U using Tapatalk

Share this post


Link to post
Share on other sites

I could be wrong. The pcv valve is on the passenger side valve cover. It runs along to the drivers side....but I don’t remember if it connects to the drivers side...or goes over to the intake 

Share this post


Link to post
Share on other sites

There are two coolant lines running to the throttle body. One of them comes from the coolant rail on the back of the heads, located behind the Bank 2 head (Driver Side). As for size, I’m fairly certain it’s 1/4”. The other hose to the throttle body extends down under the intake boot, running along the heater core pipe along the side of the engine above the exhaust manifold.

There are two sections to the PCV System. The valve itself is located on the intake side of the Bank 1 valve covers, on the back of the valve cover. It is a small plastic piece that is inserted into a rubber grommet, on the 2001 VQ. The valve itself is rather fragile, and if the hose back there has dry-rotted, you’ll have some difficulty removing it.
This valve feeds the crankcase gases into a tube under the lower intake manifold, and exits into the intake near the butterfly valves above cylinder 4.

The secondary part of the PCV is an extension of the chambers within the valve covers. The valve covers on the 2001 VQ are large and typically made of aluminum, having chambers at the top for the gases to collect. On the Bank 1 side, there is a large outlet (about 1/2”) that utilizes a hose along the top of the timing cover to reach the other valve cover. The inlet on that side is roughly the same position as the Bank 1 side, but mirrored. There is then a large outlet on the back of the Bank 2 valve cover, on the exhaust side, which feeds directly into the intake boot, before the throttle body.

It is a rather efficient PCV system, and I don’t recommend tampering with it. The VQ is quite sensitive to crankcase pressure, and will often react with oil seepage, misfires, or moisture buildup in the oil. It’s cumbersome, but it works.

e33dc8fdd174bbfe62e0c09ba3a76306.jpg

Above is a picture of my engine stripped down to the heads. I highlighted the PCV path along the valve covers with yellow.

  • Like 1

Share this post


Link to post
Share on other sites

At this point, at least on the 2001 models with the cable driven throttle body, I'm pretty certain the PCV vent can't be going into the throttle body or anything before it including the plastic  intake boot. I can't see the hose at all. All I see is the hose coming out of the driver side valve cover into the intake boot. 

 

Should the oil catch can go off the driver vent and into the intake boot? I thought I saw on another forum where someone said that was the wrong place for it, they tried it anyway because it was easy to access, and they didn't collect any oil.

 

If not, I'm not sure that the PCV valve side can be plumbed into an oil catch can without removing the upper intake. It doesn't seem there would be any clearance under there even after removing the throttle body, if it enters the metal intake runner behind the throttle body. And that's the only place left I could see it could be.

Share this post


Link to post
Share on other sites
6 minutes ago, QuasarDecimari said:

There are two coolant lines running to the throttle body. One of them comes from the coolant rail on the back of the heads, located behind the Bank 2 head (Driver Side). As for size, I’m fairly certain it’s 1/4”. The other hose to the throttle body extends down under the intake boot, running along the heater core pipe along the side of the engine above the exhaust manifold.

There are two sections to the PCV System. The valve itself is located on the intake side of the Bank 1 valve covers, on the back of the valve cover. It is a small plastic piece that is inserted into a rubber grommet, on the 2001 VQ. The valve itself is rather fragile, and if the hose back there has dry-rotted, you’ll have some difficulty removing it.
This valve feeds the crankcase gases into a tube under the lower intake manifold, and exits into the intake near the butterfly valves above cylinder 4.

The secondary part of the PCV is an extension of the chambers within the valve covers. The valve covers on the 2001 VQ are large and typically made of aluminum, having chambers at the top for the gases to collect. On the Bank 1 side, there is a large outlet (about 1/2”) that utilizes a hose along the top of the timing cover to reach the other valve cover. The inlet on that side is roughly the same position as the Bank 1 side, but mirrored. There is then a large outlet on the back of the Bank 2 valve cover, on the exhaust side, which feeds directly into the intake boot, before the throttle body.

It is a rather efficient PCV system, and I don’t recommend tampering with it. The VQ is quite sensitive to crankcase pressure, and will often react with oil seepage, misfires, or moisture buildup in the oil. It’s cumbersome, but it works.

e33dc8fdd174bbfe62e0c09ba3a76306.jpg

Above is a picture of my engine stripped down to the heads. I highlighted the PCV path along the valve covers with yellow.

 

Thanks for the detail. I've seen a lot of other threads that suggest installing a catch can on these particular engines as they age. Yours is the first recommending against it. 

 

I've spent $1,000 over 3 years replacing the valve cover gaskets twice (really 3 times but the 3rd was covered under the 2nd replacement warranty) to stop the smoky smell. I'm still losing about 1 qt per month (about every 1,200 miles). Not sure if that is the engine eating it, or leaking during operation at this point. Though I'd like to figure out. It used substantially less than that until about 3 years ago.

 

Guess I'll have to 2nd guess the catch can.

 

Share this post


Link to post
Share on other sites
 
I've spent $1,000 over 3 years replacing the valve cover gaskets twice (really 3 times but the 3rd was covered under the 2nd replacement warranty) to stop the smoky smell. I'm still losing about 1 qt per month (about every 1,200 miles). Not sure if that is the engine eating it, or leaking during operation at this point.
 


I’m currently in the middle of building my second VQ, converting a 2004 VQ so it can be used in my 2001 pathy. I can say I’ve gotten pretty personal with these engines haha.
If your engine is eating enough oil through the PCV to actually consume it, you’ve got much bigger problems than anything a catch will fix. Have you or the mechanic replaced the PCV valve itself, or tested that it functions? If not, for $5 and a couple hours of work you can do it yourself pretty easy.

Can you see any visible oil leaks? If so, where from? Is there lots of blue/black smoke from the exhaust? Where does the smell seem to originate from?

We have a lot of options to test this.

Share this post


Link to post
Share on other sites

I didn't think to specifically ask the mechanics to check and replace the PCV valve as necessary. But the 2nd mechanic to do the 2nd and 3rd valve cover gaskets has an excellent reputation and I assume he would have at least checked it.

 

There was actually a 3rd mechanic between the 1st and 2nd valve cover gasket replacements, who said I had a leak there, and at the rear main seal, and the oil pan. It's such an oily mess down there I don't know how they can tell. The mechanic who did the 2nd/3rd valve cover gasket replacement, said he didn't see other oil leaks he could identify.

 

The obvious oil leaks on the pavement, and the burning oil smell when not moving, have stopped after the 3rd valve cover gasket replacement. The smell had been coming from under the hood. Occasionally I had seen a tiny wisp of smoke from under the hood. And as the 1st and 2nd valve cover gaskets started failing, it started losing 2 quarts a month. There is oil all over the bottom end of the engine front to back. It probably contributed to 2 alternator deaths on me. By the time I got it in each time, it was losing 1 quart every 2 days. There was oil all over the pavement at the back of the engine at that point. 

 

There is a little carbon in the tail pipe. But it doesn't seem oily or smoky, just more "gassy" smelling then when it had fewer miles on it. But that isn't a bother except when I'm hooking up my trailer.

 

I had read in one thread that these engines tend to have a little too much taper in the bore, and loose oil control rings that lead to oil consumption, especially when decelerating under high manifold vacuum. And that the PCV baffle system on the passenger side is poor, and there is a revised valve cover to address it. I have no idea if there is any truth to that. 

 

I can replace the PCV valve this fall when the weather's better. It is mildly frustrating it is such a long job for something that should be easy to check/replace, and may not be a problem.

 

I didn't expect the oil catch can to really fix anything. It was more to see if there is a more extensive issue internally to the engine, recover some octane lost if there is lots of oil mist coming through, and help decide if I should double down on looking for more leaks.

 

It is a manual transmission, so no power control valves or screws to fall out. Also from looking at the engine, and reviewing the FSM, it appears there is no oil heat exchanger to leak on the manual transmission engines like is common with the automatic transmission engines.

 

Any ideas you have would be welcome. Thanks.

Share this post


Link to post
Share on other sites

Check your oil cooler for leaks 

Share this post


Link to post
Share on other sites
Check your oil cooler for leaks 
Best I can tell from looking at mine, and the FSM, manual transmission Pathfinders don't have an oil cooler. Is that not true?

Sent from my SM-N950U using Tapatalk

Share this post


Link to post
Share on other sites

Easy way to tell is to look at the oil filter. The oil cooler is the oil filter adapter. If the filter threads onto a can that has 2 hoses attached to it, then you have an oil cooler and the o-ring seal is probably leaking. It is very easy to replace the seal. Take the filter off, put a deep socket onto the hex of the filter stud and unscrew the filter stud. Pull the cooler away from the engine and replace the o-ring. Reassemble by threading the filter stud back in and tighten it down. 

 

I suggest degreasing the engine and just let it run for a little while without actually driving to see where the oil is leaking from. The most common oil leaks on the VG and the VQ engines are the valve cover gasket and the oil cooler. A commonly missed oil leak on the VG is the camshaft bore block off plate on the back side of the heads. The bolts tend to loosen over time and the gasket gets hard so that the oil will flow out the back of the head. It is often mistaken for a leaking valve cover gasket because it is up high and hard to see. 

  • Like 2

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


Welcome to NPORA Forums

 

Please REGISTER to gain full access to the forum.

Make sure you read the Forum Guidelines and don't forget to post a new intro in the New People Start Here! section, to say hi too everyone.

 

-NPORA

×
×
  • Create New...