1991 Q45a Oil Leak

[azskygod]

Yeah, unfortunately I will be an "experienced" tech by the time I'm done! First the plenum job, and now the chain guides...

AZSKYGOD

[texasoil]

doesn't sound pretty. The lifter clatter is bad, there is a deeper knock that sounds like loose bottom end bearings, and the lope during cranking is not a good sound. Possible timing chain slip would account for lope, deep knocking sounds like no oil in the rod bearings.

Checkoil pressure ASAP during cranking, plugs out (minimum load on rods and mains.

[azskygod]

Well, I couldn't locate and remove the oil pressure sender. I know where it's supposed to be, but there just wasn't enough access with all of the active suspension stuff in that area. So instead of wasting valuable time, I decided to disassemble again and retime.

The work went quickly, especially since I had some help this time. My brother owns a non-active 93 Q, and graciously offered to help. (THANK YOU!) In 6 hours, we got everything stripped and ready to remove the valve covers next weekend. A few technical taps with a rubber mallet is all that's left to do. The driver's side chain definitely jumped time -- we actually watched it happen again while slowly turning the crankshaft. Oil was found in a couple of the plug wells too, so I guess it was time for a reseal anyway.

I'm going to attach some photos showing 214k miles of wear on the old vs. new style chain guides. I find it interesting how the new guides sandwich the chain, while the old ones don't.

AZSKYGOD

[azskygod]

Check out how the chain has worn grooves into the plastic...

[azskygod]

The new style guides (top) are metal-backed and have an extra plastic piece that sandwiches the chain. The old style guides (bottom) are one large piece of plastic...

[azskygod]

Texasoil, I think the "deep knocking sounds" you heard were actually normal intake and exhaust noises echoed against a (closed) metal garage door in an enclosed space. The clatter is definitely coming from the driver's side valve cover, but I don't hear any bottom-end knock. I agree, the cranking lope is what makes me suspect it has jumped time.

AZSKYGOD

[Q451990]

Hopefully you caught it in time and didn't bend any valves. If it was still running you probably did. Any idea why it was jumping time?

Heath

[azskygod]

The first time, it must have jumped a tooth when the broken chain guide fell into the oil pump drive. That would explain the stretched oil pump chain, the broken metal tab and cover, and the valve train noise after reassembly.

The second time, it jumped because there wasn't enough tension on the chain when we turned the crankshaft. We're going to prime the oil pump for a few minutes with a drill and a socket to get the tensioners and HLA's pumped up before reassembly this time!

AZSKYGOD

[Q451990]

I think you'll find just a few spins of the oil pump sprocket will send a lot of oil through the system. I'd think you'll be able to feel the tensioners to see if they're pumped up - but I'm not sure.

Byron gave my oil pump a quick spin by hand before putting the new chain on and it looked like a shower in there. He said it definately reduced the amount of initial start-up rattle compared to the others that he's done (I think that's about 100 or so units).

I'd still strongly consider replacing the oil pump while you're in there but at your mileage it's a judgment call...

Heath

[azskygod]

Sometimes, it's good when things go wrong. I found some stuff that would have gone totally unnoticed if I had not torn everything back apart again to redo the timing. We pulled the valve covers today. The passenger side was easy -- I didn't even have to remove the fuel lines. The drivers side required the removal of the TB, the EGR, the PCV hose, and the EGR vacuum solenoids. It was tight, so replacing them with a full load of RTV should provide hours of entertainment.

I was impressed at how clean the heads were for 214k miles! I drive a LOT of highway miles. I usually add a quart of MMO a few days before changing the oil (between 3-5k miles) with Castrol GTX. Absolutely no sludge found and everything looks clean. Sweet!

I did find a piece of chain guide UNDER the valve cover on the passenger's side. Chunks of guide must have been really flying around to land in there! Check it out.

[azskygod]

I don't know much about how to read cam lobe wear, but here's a photo for those who do. This is a photo of the exhaust cam lobes for cylinder #2. The rest look very similar with slight polishing on the outside edges...

[azskygod]

Here's the reason why I'm actually GLAD we had to redo this job. My brother noticed a bent link in the driver's side timing chain, so we removed it for closer inspection. The underside of the chain revealed a broken link, and many deep gouges in the adjacent links. This link would have eventually failed and totalled my engine! (The passenger side chain was fine.)

I'm guessing this section of the chain is where the chain guide fell into, rotated below the crankshaft, and broke the metal tab off of the lower timing chain cover. Did I mention I was lucky?

[azskygod]

That's it for this weekend. I'll order chains from Joe tomorrow, and retime and reassemble everything next weekend. Finally, here's one last photo to remind myself of the amount of work involved in this repair, since my brain tends to block out these kinds of wonderful memories over time...

AZSKYGOD

[DAEDALUS]

Yes, VERY lucky. Still hoping you get it running well again. The lobes "look" good, but hard to tell from a picture. Drag your nail across the surface of the lobe...can you feel a ridge where it goes from shiny metal to the stained bronze edge? That's the amount of wear on there. It'll be greatest near the tip of the lobe on the forward edge. Factory specs allow for about .008" of wear, which is about 2-3 sheets of paper. If you're really curious you can just remove the bearing caps and pull them to measure. Probably not something you need to worry too much about, at least relative to everything else going on over there.

[Q45tech]

Did you release the tension on the oil pump guide it looks like it has been adjusted to the totally slack position?

Vibration of chain could have loosened the nut?

But again it lasted 214k and over 12 years what more could anyone ask.

Back in 1991, no one on EARTH would have sold you a 200,000 mile engine policy for less than $5,000..........time and history has taught us how to make them last 300k........now.

[azskygod]

Success! Finally, after many weekends of work on the Death Machine, it's running strong again!

It took most of the weekend to put everything back together after the retime. Installing the new chains was easy thanks to the marks on the sprockets and the silver and gold colored links on the chains. So easy, in fact, that I found myself double and triple checking my work just to make sure. Here's a photo of the chain alignment marks on the passenger side...

[squeefoo]

Very, Very Cool. I hope she purrs like a Rolex for you now.Let us know how she runs. I'm sure you will.

:jump

[azskygod]

Reassembling everything was fairly straightforward, but I spent a lot of time preparing the mating surfaces and removing the old RTV. No chemicals, just a few abrasive nylon pads (Black & Decker), lots of scrubbing, and a final wipe down with some 90% Isopropyl alcohol.

I highly recommend the Nissan Silicone Gasket over any other brand of RTV. It's orange and it's expensive, but it seems to cling to bare metal better than Permatex or anything else. Replacing the passenger side valve cover was easy. I applied a bead of RTV to the cover, and spread a thin coat on the heads before reassembly. The driver's side required 2 people, but wasn't nearly as difficult as I had imagined. I did remove the charcoal canister and the metal PCV tube on the rear of the valve cover to make things a little easier on myself. (The metal pipe sticking out from under the plenum on the driver's side sure got in the way.)

Here's a photo of how clean the mating surfaces were after about an hour of cleanup...

[azskygod]

I estimate there were about 100 bolts involved in the entire job. Many thanks to my brother for his awesome punch-the-hole-through-the-cardboard engine diagram. It was crude, but it made reassembly so easy and we didn't end up with any left-over parts!

[azskygod]

It sure was nice to start putting things back together instead of taking them apart. So, here's the obligatory BEFORE photo...

[azskygod]

...and the amazing (because I remembered where everything goes, and in what order) AFTER photo...

[PalmerWMD]

Yayyyy!!!

Fred..:fruit

[azskygod]

I finished the final assembly at about 11pm Sunday, topped off all of the fluids and installed the battery. After about 16 hours of work it was ready to go, but I had to wait another 24 hours for the RTV to cure.

At 6pm Monday, I attached the positive battery cable, climbed into the driver's seat, inserted the key, relaxed and tried to imagine the sound of a purring Q45 engine...

I turned the key and it immediately started and sounded PERFECT! I could hear a faint ticking sound as the passenger side tensioner pumped up (I filled the driver's side with oil before inserting it) that slowly faded away after about a minute. No other unusual noises at all. It sounded beautiful!

Muhahaha! A quick drive into the sunset down Sun Valley Parkway (home of the 160mph speed run) confirmed that the engine was still healthy and very strong. I firmly planted my right foot and remembered why repairing the Death Machine was so important to me. A few minutes later -- with a huge grin on my face -- I regained my sanity and slowed down a little.

What a learning experience. (Did I mention I was lucky?)

I would like to thank everyone who took the time to respond to this thread with words of wisdom and support, and I hope the information and photos will eventually help someone else. I've been with this group since the days of Yahoo (lurking and learning) and it feels good to be able to contribute. This really is THE BEST place for enthusiastic Infiniti Q45 owners like me. Thanks guys.

Long live the Death Machine!

AZSKYGOD

[Q451990]

:ylsuper :beer :beer :beer :beer :beer

Can you tell I'm happy! I was sure there was bad news after the first try - glad to hear it all worked out!!!

Heath

[DAEDALUS]

Way to go!

[maxnix]

Quite an accomplishment! Glad a G50 Q45 was rescued for another life rather than discarded like a disposable Chevy. May your rewards last long and your pleasure be great.

[911/Q45]

That cardboard fastener diagram is about the cleverest thing I've seen in years!

[azskygod]

Yeah, my brother is one clever dude. He wanted to see how difficult it would be to reseal his own leaking valve cover and offered to help. I think he's sufficiently intimidated now that he won't be doing it anytime soon -- at least not without my expert help. Ha!

(Thanks again, Longduck. I owe you one.)

AZSKYGOD

[SOCAL91Q45a]

Jeeezum Crow - a truly amazing story!!! azskygod - you rock brother. Congrats!

When i do my motor and head swap in my 90a out in Landers, CA perhaps i can convince you to drive out and party and give guidance :-)

[psychic_mechanic]

That cardboard thing is even better than freezer bags and a permanent marker.

Congratulations and getting it back together!