morning ladies & gentlemen, currently driving a 4th gen 95 maxima, & I've come to learn that i have a rear main seal leak, right where the motor meets the tranny. i have been informed that to fix that seal, i am going to have to pull the motor. since i am already pulling the motor out of the 95, i was thinking about instead just swapping in a 98, only because the 98 has been slightly rebuilt making it more dependable . has anyone previously done this or knows if it would be compatible? i have spoken to multiple nissan technicians, & most dont see why it wouldnt work, but havent personally done the swap. any help you can give would be greatly appreciated!!

 

I've had a 95 model swapped into 99. Are both engines from Automatics or manual?

Check the bottom side of the intake plenum (by the place where the throttle body connects) for a difference between with the intake plenum between a 95 and 98 model.

 

--- both are automatics. i am currently at work, so i cant say forsure until later today, but i am 85% sure they match. any recommendations you can give or other problems you came across while swapping?

 

Automatic to Automatic should be fine. Its when we went from a 95 model automatic to a manual where we found there is a part off of the crankshaft that is different between automatics and manuals.

Now I remember the hose difference is on the top.

Take a look at the 1995 FSM EC diagrams on page 13 of the diagram at the following link.

http://www.boredmder.com/FSMs/Nissan/Maxima/1995/EC.pdf

Here's a picture of the intake plenum from my 98 model below. I started trying to use an intake plenum from a 1995 model that I had polished for the replacement before I noticed the following difference and had to go with the original one from the 1998 model.



The vacuum hose drawing for a 98 model is on page 18 of this EC section below.

http://www.boredmder.com/FSMs/Nissan/Maxima/1998/EC.pdf

 

You could do the same work by pulling the crossmember and tranny. If it aint broke dont fix (replace) it-Don't replace your engine. It's more likely the half-moon seal between the bearing cap and upper oil pan, so make sure that gets replaced too.

 

+1 The half moon is the most likely source of the leak. If a mechanic is not familiar with the VQ30DE, they will say the leak is from a main seal instead of a half moon gasket.

Here's a picture of a front half moon that is under the timing cover that mates up with the upper oil pan. There is a half moon like this one at rear of the engine.

Old Front Half Moon



Front Half Moon Replaced

 

-----UPDATE----
Decided to take your advice, seeing as how a water pump & seal replacement is much less work, & also now is dire. Will post more updates & pics as i begin to take it piece by piece, i do appreciate the help very much so. Do you by chance have any tricks on getting the tranny out without all the disconnecting? Im quite literally going by the book here, & they want starter, battery/tray, intake etc..

 

You can replace the upper oil pan half moon seals without pulling the transmission. It's a matter of dropping the upper oil pan versus the transmission. There's another thread here that shows the back of the engine.

In this thread, you can see how the upper oil pan connects to the block. It looks like the lower 1/2 of the block in the picture in this thread.

https://maxima.org/forums/4th-genera...eal-bolts.html


Here's a picture of the rear of the upper oil pan where the rear half moon is located.



Here's a picture of the upper oil pan from the bottom.

 

Ok so, ive gotten a bit into the engine & i can see it isnt the water pump that is leaking. Ive checked the outer edges of the pump case & it is relatively dry compared to the leak. The leak is accumulating between a/c compressor & front of oil pan, but i cant seem to find the leak itself. Any ideas?

 

Could the oil be running down from the corner of the valve cover to drip on the alternator and compressor?

Also, I had a small leak on the corner of the timing cover right at the tip over that is near the alternator. I was able to stop the timing cover leak by "CAREFULLY" re-torquing the (10mm) timing cover bolts. The bolts had become loose over the years from vibration and from the RTV shrinking. I got lucky on that one because most of the time I would have had to pulled the timing cover and resealed it with RTV. DO NOT over torque the timing cover bolts because they are easy to break off.