12 January 2016

This month’s column concerns anoil leak that develops on somepopular Nissan V6 engines. Staytuned, though, because this oneis not your typical oil leak. Here’sthe lowdown.

Wayne Lawson is the Nissan specialist atCustom Car Care in Yorktown, VA. He told methat an internal oil leak may occur in Nissan’s4.0L V6 power plant. (Nissan introduced thisengine in 2005.) So far, he has seen the prob-lem in Pathfinders, Xterras and Frontiersequipped with this V6.

Usually the owner brings the vehicle in be-cause its oil warning light is on. Often theCheck Engine light is on, too, and the ECMhas stored two DTCs for the valve timing con-trol (VTC) system. The trouble codes areDTCs P0011 and P0022. Mind you, some tech-nicians may jump to the conclusion that the en-gine is low on oil. But Lawson explained that,first and foremost, the oil level is okay. The af-fected vehicles are in good condition and havebeen maintained. Also, there are no complaintsabout abnormal or excessive engine noise.

Another clue is that the oil warning lightgoes out when you rev the engine. If the ve-hicle has an OE oil pressure gauge, it showslow oil pressure at idle. But then the gaugereading increases steadily as you rev the en-gine. Oil pressure looks normal at higherrpm. So, the condition appears to be an idle-related oil pressure problem.

Lawson emphasized that he doesn’t take oilwarning light or OE gauge operation forgranted. Instead, he has tested each vehiclewith his own pressure gauge. Every time, hisgauge confirmed that the V6’s oil pressure waslow at idle but only a bit lower than spec athigher rpm.

A leak inside the engine’s front timing cov-er assembly causes this problem, Lawsonsaid. This assembly, which techs often callthe “front cover,” actually contains two sepa-rate aluminum castings. The casting closestto the engine block is the inner or rear cover.The photo on this page shows the engine sideor back side of the inner cover. Meanwhilethe outer or front cover mounts onto thisone. The blue paper arrow in the photo onpage 14 points to the location of an internalleak that causes the low oil pressure symp-toms, Lawson said.

Note two important details on this combi-nation of front/rear timing covers. First, youmust remove the front cover and the timingchains in order to access the rear cover. Sec-ond, there are no traditional gaskets on thesecovers; when you reinstall these timing covers,you have to reseal them with RTV silicone (a ka liquid gasket). What’s more, allow ampletime for cleaning off Nissan’s original RTVsealer. I’m not aware of a fast, easy way to re-move the OE liquid gasket without damaginganything. Predictably, you also have to be pa-tient and careful when you run new beads ofRTV sealer on these timing covers.

Lawson showed me two contoured steelplates inside this V6’s rear timing cover. (Onceagain, inside means the engine block side.)

If an engine with a full crankcase develops lower-than-normal oil

pressure, worn bearings may be the cause. But on some Nissan

engines, there’s another place where pressure can be lost.

Foreign Service

DanMarinucci

dmarinucci@motor.com

This is the engine side of the rear or inner timing cover used on certain Nissan V6engines. A gasket failure on this side may cause an internal oil leak.

Pho

tos:

Dan

Mar

inu

cci

FOREIGN SERVICE Jan 2016_Layout 1 12/15/15 7:03 AM Page 12

when there’s a piece of gasket missing.

As of press time, neither Lawsonnor I have found a supplier of re-placement gaskets for these steelplates. The only repair option seemsto be replacing the entire rear timingcover on this V6 with an OE part. Re-portedly, the part number of this reartiming cover has been updated sever-al times; perhaps that means the rearcover itself also has been revised.

Last but not least, you may wonderif the Phillips-head screws holding thesteel plates in place worked loose.Lawson said he’s checked them everytime but hasn’t found any that felt theleast bit loose. If the tightness on allof them feels the same, then loosenedscrews don’t seem to be a likely causeof the gap in the upper plate’s gasket.

Hopefully, these details help youout when you encounter the low oilpressure symptoms on certain NissanV6 engines. Meantime, keep smilingand I’ll look for you next time.

Foreign Service

the gasket gap. When in doubt, hesaid, try to slide a thin feeler gaugeinto that location. Typically, the feel-er gauge slides right under the steelplate—with no resistance to it—

14 January 2016

Whenever he’s run into the symp-toms mentioned earlier, he’s found abig gap in the gasket under the up-per steel plate. The blue arrow in thephoto below shows the location of

The blue paper arrow indicates where a chunk of gasket material may come out of the rear timing cover. A replacement gasket is not currently available.

Circle #9

FOREIGN SERVICE Jan 2016_Layout 1 12/15/15 7:10 AM Page 14