Just wondering if anyone has actually had their timing belt break on a 6B31 3.0L V6?

These two sources show this engine as a non-interference design:
Mitsubishi Timing Parts
http://www.gates.com/common/download...ementGuide.pdf

I can't find any reputable sources (service reps trying to talk me into service are not reputable IMHO) that say that this engine will self-destruct upon CAM belt breakage or slippage.

It may just be bad luck on my part, or maybe it's because I drive every last mile that I can out of my cars, but I've experienced 3 timing belt breaks during the last 20 years. The first was a Nissan Sentra (interference design) that went out at 65K miles (5K past where I should have replaced it) while climbing a hill at 5k RPM. This was a major and heart-breaking disaster. I've never been able to bring myself to buy another interference engine since. This tradition has been reinforced by being able to drive both a Mercury Villager and Ford Escort for over 100K miles (combined) after their belts broke. Interestingly both these belts broke within 20k miles of being replaced, so following the maintenance schedule doesn't guarantee anything at all.

I've found on most car forums (and this one is no exception) that the consensus is that any modern high performance engine with variable valve timing must also be a valve bender. This is often true, but not always the case.

I've found a very good price on a low mileage and well serviced 2007 V6 AWD Outlander LS. I'd like to buy it and would really get a nice warm fuzzy feeling if someone can confirm that their 6B31 timing belt broke and they were able to just replace it and continue on their way.

 

the general concensus is to start thinking about chanigng out the belt at 100k miles. I'm just past that and I'm thinking about when I can change mine out and put a Goodyear GatorBack belt in there...I've heard great comments from many sources about that belt in general. I have also heard that the motor will die if it breaks. As I understand it, the cams stop moving...so the valves stop moving, and the pistons and hit the valves to bend them.

I had a '93 Eclipse with the 1.8L engine where the belt broke on me. Luckily I was doing about 15mph and it was a manual. When the lights lit up, I hit the clutch and pulled over. Mechanic said I was lucky as a few months before that, a lady was on the interstate in the same kind of car and the belt broke...destroying the engine. For weeks before mine broke, I kept hearing a TAP...TAP...TAP from somewhere in the engine...never could figure out what it was, but was in sync with RPMs. it was the belt slowly coming apart.

I know the recommended mileage is 100k on the 3.0L. the top cam gears are pretty easy to get the covers off and inspect the belt. I last inspected mine at 95k miles and the belt looked to be in great shape...just the slightest bit of feathering on the sides...but otherwise great shape.

 

The 1.8L 4G37 motor is not an interference engine. You may as well have been red-lining in a 92HP quarter mile race. It still would have come right back to life after installing a new belt.

Your mechanic's lady probably had an Eclipse with a variant of the much more popular 2.0L 4G63 motor, which was an infamous valve-bender.

Interference engines are VERY fragile if the belt breaks. The only "luck" you can have with them is if you only have to redo the top end instead of replacing the whole motor. Their valves can even be inadvertently bent by doing nothing more than being a fool and turning the cam or crankshaft when swapping out the belt.

In all my searching I have found several claims that the Outlander has an interference engine, but nobody has complained about bent valves. This is an unheard of combination given the age of the current design. I think it can pretty safely be said that any 2004-2013 Outlander with a CAM belt, be it either a 2.4L or 3.0L, doesn't have an interference engine.

 

A quick check of my owners manual (2012 GT w/3.0) does not say if these ae interference engines or not.

I would guess that they are

 

Kind of off topic, but what year sentra did you have that required a timing belt? I never seen a 4cyl nissan that used a timing belt. All models that I can think of since the early 90's used timing chains that are practically indestructible.

 

This may be the case. My Sentra was a 1988 that I bought used in 1994 with only 62K miles it. This was the first car I ever bought. I think it had a 1.6L engine. I only had it about 3-4 months when the belt went out. I recollect that at least one piston shattered and the engine was completely shot. What I remember best of all was making payments on a dead car for what seamed like forever while waiting to save up the money for a new (used Japanese) motor.

I any case, the lack of response (other than the minimum one internet mandatory hearsay response) pretty well indicates that the Outlander V6 is most likely not an interference design and I can rest easy buying it.

 

I called up Mitsibishi Motors North America and asked if the 6B31 was interference or not...after a 5 min wait on hold, "All of our engines are interference engines."

1-888-MITSU2012 (1-888-648-7820)

 

I just talked to a Mits mechanic of 10 years who I believe really knew what he was talking about.

Look at the below piston drawings from the 2007 service manual. They pretty clearly show divots in the top of the piston for the valves. These divots are also called "non-interference reliefs".

From 2007-2009, the 6B31 3.0L V6 engine had these pistons along with a compression ratio of 9.5:1 and were non-interfering if the timing belt broke.

However, beginning in 2010 in order to try and keep up with competition, Mitsubishi "upgraded" the pistons. They got rid of the divots and slightly lengthened the connecting rod. This increased compression to 10.5:1 and also increased output from 220hp to 230hp. Unfortunately this also eliminated the non-interference design of the engine.

The mechanic said he'd only seen 2 timing belt breaks on 2007-2009 V6 Outlanders and neither resulted in engine damage. He hadn't seen any breaks on 2010+ Outlanders. He recommended inspecting the belt at 60K miles and replacing it at 105K miles, especially on 2010+ models

So there we have it. 2007-2009 Outlanders just need a new belt if it breaks. 2010+ models will also, at the very least, require a top-end rebuild.

 

You know, that make a lot of sense. That is awesome. That makes me a lot less nervous about running the belt a bit longer. thank you very much for looking that far into the subject!

 

Thank you for the info O-lander!