2001 Pathfinder Rear Main Seal/Water Control Valve gasket Replacement - Pulling Engine?

[chris53378]

Heyo!

 

Got a 01 LE 3.5 Pathfinder with 206k on it, I've owned it for about 8 years and the rear main seal is toast. It's progressively worsened over the past couple years from a few drops to now where I go through 5 quarts of oil every week and half or so (I do A LOT of driving for work) It's time I tackle it, with help of my mechanic brother and his tools.

 

today I noticed I am also leaking coolant from where the water control valve connects to the engine. It's on the rear center of the engine where the coolant exits the cylinder blocks, in a tight space. I cant keep pissing away oil and coolant anymore.

 

FSM says to remove transmission for rear main seal, but replacing the water control valve gasket would be easiest if I pulled the engine out with a cherry picker. My question is, can I do the rear main seal by pulling the engine without dropping the trans? It would give me room to work on the whole metal water outlet, and kill two birds with one stone.

 

I know for a fact I want to replace as many gaskets and clean as many mating surfaces as possible without completely deconstructing the engine. Also I'd like to replace any hard to reach coolant lines. I'm pretty broke at the moment so when I do this job I want to prioritize doing whatever preventative maintenance I can without breaking the bank.

 

I've done some research but I need to develop a plan of attack. I've done a lot of work on this car myself so I know I can handle it with my brothers help. If anyone has any suggestions, experience, or other resources like parts lists I'd greatly appreciate them!

[hawairish]

You can access the water control valve and crossover pipe and gaskets with the transmission removed. That’s how I did it. It’s still a little tight, but you can tip the engine forward a small amount…as long as the mounts aren’t toast and it wants to just fall forward. 
 

However, there’s the RMS itself and a seal around the plate that holds the RMS. The failure point is usually the seal around the plate and not the RMS itself, which is what requires separating the upper oil pan (the black pan you see is the lower pan) from the block. To separate the upper pan and the block there’s a lot of other things that need to be loosened or removed. When I was in there to address my leak (not nearly

as as bad as yours), I just slathered some RTV along the plate seal. 
 

As for pulling the engine instead and leaving the transmission in…I think pulling the transmission (and t-case) down is the easier route. That way to don’t have to disconnect all the electrical and exhaust stuff. Pulling the transmission just needs detaching the driveshaft, unplugging the harness pigtail, and detaching the ATF lines. Get a transmission jack. 

[chris53378]

On 1/22/2025 at 11:46 AM, hawairish said:

You can access the water control valve and crossover pipe and gaskets with the transmission removed. That’s how I did it. It’s still a little tight, but you can tip the engine forward a small amount…as long as the mounts aren’t toast and it wants to just fall forward. 

Thanks for the advice. Part of the reason I was thinking take the engine out was because I don't have access to a two post lift, I can certainly get some clearance to work under the truck with jack stands but thought maybe pulling the engine would allow me to work with more space.

 

Is it physically possible to even do the RMS without dropping the trans? (by only pulling the engine, even though it's quite a bit of work)

 

 

[hawairish]

2 hours ago, chris53378 said:

Thanks for the advice. Part of the reason I was thinking take the engine out was because I don't have access to a two post lift, I can certainly get some clearance to work under the truck with jack stands but thought maybe pulling the engine would allow me to work with more space.

 

Is it physically possible to even do the RMS without dropping the trans? (by only pulling the engine, even though it's quite a bit of work)

 

 

 

I need to be super clear that the level of work I've described so far was specifically to service the crossover pipe.  That means I need to pull back most details about my experience because they will not be the same as yours if you need to replace your RMS.  My apologies for not realizing or stating this earlier.  That said...

 

Replacing the RMS on this truck requires a SIGNIFICANT amount of effort and equipment.

 

In my case, I had zero intentions of replacing it because I knew the amount of work it required.  I intended to apply RTV to the exterior of the RMS to seal a minor leak I was aware of.  If you're losing that much oil, this is surely not the option you'd take.

 

To replace the RMS, we're talking about pulling the transmission, draining coolant and motor oil, dropping the front axle, slinging the engine, lowering the subframe, and splitting the engine.  The factory service manual assumes you have access to a 2/4-post lift, a cherry picker/hoist, and a transmission or trolley jack.

 

To your point, pulling the engine could be the home mechanic way to do this job...but not the best way.  In essence, you need to support the engine from above while the subframe is lowered to provide space to drop the upper oil pan.  I'm trying to finish a straight axle swap and for the last 10-11 months, I'd been using an engine support bar to suspend the engine, which is really all you need to do here.

 

 

I thought I had a better pic, but you can find these at Harbor Freight or on Amazon.  I got mine from Amazon for about $80 I think.

 

I can tell you firsthand that slinging options on this engine absolutely suck.  The factory sling points are in the dumbest locations, and you basically need factory slingers to even use them (one point is behind the power steering pump, which must be removed to access, but the points are tucked in an obscure spot...can't just put a bolt in and use it with chains; the driver's side spot is a little more accessible but also not usable with the support bar.  There are no exposed bolt holes, no clear paths to wrap a strap around without compressing against coolant hard lines/pipes or wiring, nothing to chain to...it's absolute crap.  In that pic, I made a plate that bolts where the power steering pump goes, but I eventually replaced it with one that attaches to the brackets that hold the motor mounts.  My slingers are basically permanent fixtures on the engine at this point for future use.  You could potentially make a sling plate that bolts onto the intake manifold (i.e., the actual manifold on the engine underneath the intake plenums), but frankly, I didn't like that option at all.  

 

You can drop the transmission without slinging the engine.  And you probably should do this first to determine what part of the RMS is actually leaking.  But with the engine slung, you can do all the work necessary to lower the subframe.  You'll also avoid having to disconnect engine harnesses, detach the exhaust system, split the A/C, and many many other things...it will still be a lot of work, but it will save a lot of time and possibly money (recharging AC lines).

 

If you're not familiar with the Factory Service Manuals, get familiar: https://www.nicoclub.com/nissan-service-manuals

 

Drill down into Pathfinder > 2001 or 2001.5 > Engine Mechanical.  In that chapter, start at with page EM-15.  You'll quickly see the major steps that are involved.  If you start with EM-37 you'll be very disappointed that Nissan makes the procedure look like it's 6 easy steps.

 

Re: 2001 vs 2001.5...2001 was a split year.  Your exact manual will depend on your truck's manufacture date (I don't know the cut off) but the procedures here should be the same.  I recommend opening each link in a new browser tab, then clicking the "Click here to download a copy" link below each PDF inset on the page so that you can save all the PDFs to a local folder and reference later.  I like to keep mine on a Google Drive share so I can pull them up whenever.  The FSM site does not load well on mobile devices, if at all.

 

And yes, the transmission must be removed to access the RMS.  As is separating the upper oil pan from the block.  The RMS is actually a seal within a housing ("retainer").  The seal cannot be removed like a conventional RMS on the truck because it is installed from the backside of the housing.  As mentioned earlier, the seal itself does not tend to fail, but instead a seal on the perimeter of the housing.  The housing uses both a paper gasket (engine block) and rubber strip/seal (upper pan) in addition to a bead of RTV all around.  Given the volume of oil you're leaking, the rubber seal is surely compromised.  I bought the Ultra Power set from Rock Auto because it include the rubber seal; I don't think the other ones (which only show the gasket) include the rubber seal.  (If you need a replacement, send me a message and I'll send you the kit I have...I don't have a need for it at this point.)

Edited January 24, 2025 by hawairish

[chris53378]

On 1/23/2025 at 11:54 PM, hawairish said:

 

I need to be super clear that the level of work I've described so far was specifically to service the crossover pipe.  That means I need to pull back most details about my experience because they will not be the same as yours if you need to replace your RMS.  My apologies for not realizing or stating this earlier.  That said...

 

Replacing the RMS on this truck requires a SIGNIFICANT amount of effort and equipment.

 

Thank you! I really appreciate the thorough advice, I plan on doing this closer to summer so I'll update how things go and what I end up doing for any r50 owners who come across this in the future.

 

I'm getting a new job and will be able to use a company car so I'll be able to let the pathy get some well deserved rest, it's been putting in serious work for the past couple years!