Timing Belt Replacement; When is the right time?

[cr4x4cruiser]

We have two G2.5 Montero's...

1] 1999 SR 113.XXX miles

2] 1998 SR 110.XXX miles

Having just performed the replacement of valve cover gaskets on them we found striking differences in the condition of the timing belts;

Though very close in mileage [basically identical] we found #1 had a belt that appears in excellent condition, as seen through the viewing port on the passenger-side along with peeling back the driver's-side cover.

Contrarily, we found #2 to be absolutely cracked throughout. It would appear, without having maintenance records, that #2 never had a timing belt replacement performed, while #1 likely did.

#2 goes in next week for a thorough job, and #1 shortly thereafter.


As well, maintenance on the cooling system was quite opposite;

#1 appeared to never have been serviced properly - with massive amounts of crud found in the radiator/ engine/ heater core.

#2 was clean as a whistle.


Weird, but true.

Without service records one can never be sure of any services performed, ever.


Lastly, based upon all that I have culled, I believe my best option for doing the timing belt/ water pump is to piecemeal everything - specifically locating/ obtaining the majority of parts as OEM, rather than going with a kit [specifically seeking out an OEM water pump & hydraulic tensioner from AISIN/ NTN].


Wonder what that timing belt looks like? Don't be afraid... pull out a 10mm socket & remove that cover. It won't hurt a bit [yeah, that's what your dad always said]...


- Wm.

 

[Marcus2113]

Wm,

Inspection is probably the best place to start with no service records, as you already completed. My personal service recommendation is to change the timing belt, water pump, etc every 100k and no more. I wouldn't want to risk a timing belt failure past 100k, since these 3.5 SOHCs are interference engine which would result is catastrophic damage.

List of Mitsubishi Interference engines:

Mitsubishi
• 1.5L Interference
• 1.6L DOHC Interference
• 1.6L SOHC Interference
• 1.8L Interference
• 2.0L DOHC Interference
• 2.0L SOHC Interference
• 2.3L Diesel Interference
• 2.4L DOHC Interference
• 2.4L SOHC Interference
• 3.0L DOHC Interference
• 3.0L SOHC 12 Valve Engine Non-Interference
• 3.0L SOHC 24 Valve Engine Interference
• 3.5L DOHC Interference
• 3.5L SOHC Interference
• 3.8L Interference

Hope this helps.

 

[cr4x4cruiser]

Marcus,

Especially because of the fact that we are dealing with interference engines is why we will doing the timing belt replacement in the coming week...

The only place the '98 is getting driven is to the shop for the service.

Finalizing the parts list, ordering today, and looking forward to a definite peace of mind...

Thanks for your input.


- Wm.

 

[JohnnyBfromPeoria]

You can get a complete Aisin water pump (both halves) from Rock Auto. That's what I used.

John B.

 

[Marcus2113]

Wm,

As you plan to do the timing belt, I would agree with Tim to replace the water pump. We also had experienced a problem at around 125k. Here is my service interval schedule for my Montero, keeping in mind it's used primarily for extended trips. This should give you some ideas.

Service: 5,000 mile
-Engine Oil Change
-Engine Oil Filter Change
-Tire Rotation
-Grease Zerk Fittings
-Check Air Filter
-Check Brake Pads

Service: 25,000 mile
-Replace Air Filter
-Check Transfer Case Gear Oil
-Check Front/Rear Differential Gear Oil
-Bleed Brakes
-Flush Radiator and Replace coolant & Replace radiator cap
-Drain and fill Transmission Fluid with Mitsu Transmission Fluid

Service: 50,000 mile
-Replace Transfer Case Gear Oil
-Replace Front/Rear Differential Gear Oil

Service: 100,000 mile
-Replace Timing Belt and Timing Belt Tensioner
-Replace Thermostat and Water Pump
-Replace Harmonic Balancer
-Replace/Inspect all coolant hoses to include heater and throttle body heater hoses
- Replace/Inspect radiator hose clamps with Mitsu clamps
-Replace all belts (replace idler pulleys)
-Replace crank seal, cam seals, and rear cam plugs
-Replace valve cover gaskets
-Flush Transmission and replace with Mitsu Transmission Fluid
-Replace Transmission Oil Filter/gasket
-Replace Fuel Filter
-Replace Spark Plugs with Platinum Mitsubishi Plugs
-Replace Spark Plug Ignition Wires with Mitsubishi Wires
-Clean Throttle Body
-Clean Power Steering Fluid Screen and replace fluid
-Flush Fuel Injectors
-Service Evaporative Charcoal Canister
-Service emissions controls
-Replace EGR Pipe & PCV Valve
-Check Entire Exhaust System for leaks

 

[JohnnyBfromPeoria]

^That's a good list.

John B.

 

[cr4x4cruiser]

I second Johnny... your list is going into my file, seriously. Somehow it just seems more logical than the mfg's service lists...

As for the service awaiting our second Montero, here it is;


MITSUBISHI MONTERO 3.5L 1997 - 2000

TIMING BELT KIT [TBK]
TKM-500 [1] Kit, Timing Belt & Component [AISIN] RA

1300A012 [1] Pump, Water [w/ Housing, Gasket, O-Ring] [TKM-500]
1145A043 [1] Belt, Timing [MITSUBOSHI] [TKM-500]
MD341830 [1] Tensioner, Hydraulic [+ BTM500] [AISIN / NTN] [TKM-500]
MD319022 [1] Pulley, Idler [KOYO] [TKM-500]
MD140071 [1] Pulley, Tensioner [KOYO] [TKM-500]
[1] Gasket, Water Pump to Water Pump Housing [TKM-500]
MD188352 [1] Gasket, Water Pump to Block [TKM-500]
MD308723 [1] Gasket, Thermostat Case to Water Pump [TKM-500]
MD030763 [1] O-Ring, Water Pump Housing to Coolant Pipe [TKM-500]


MD308724 [1] Gasket, Thermostat Housing, Top [35700] [FEL-PRO] RA
MD372536 [2] O-Ring, Camshaft Seal, F eBay
MD350415 [1] Kit, Thermostat [1305A239: 88C/190F] [THM012] [AISIN] RA


1100A141 [1] Bolt, Crankshaft [3rd Version] eBay
MR994412 [1] Washer, Crankshaft eBay
MD372249 [1] Seal, Crankshaft, F eBay


MB660735 [1] Cap, Radiator, 13psi [MR481216] [10327] [STANT] RA
MR404371 [1] Hose, Radiator, U [22073] [GATES] RA
MR404372 [1] Hose, Radiator, L [22146] [GATES] RA


MB813344 [1] Belt, Air Conditioner [9365] [GATES] RA
MZ690247 [1] Belt, Alternator [K050446] [GATES] RA
MD186126 [1] Belt, Power Steering [K040390] [GATES] RA


MD303649 [1] Sensor, Crankshaft Position [PC191] [SMP] RA
MD320622 [1] Sensor, Camshaft Position [PC96] [SMP] RA


==========================================================


MN176208 [2] O-Ring, Camshaft Seal, R [06MAY17]
MD149764 [1] Gasket, EGR Tube [06MAY17]
MD303148 [2] Gasket, Valve Cover [06MAY17]
MD198128 [6] Grommet, Spark Plug Tube [06MAY17]
MD199282 [1] Gasket, Intake Plenum [06MAY17]


==========================================================


TRANSMISSION SERVICE
MB868452 [1] Filter, Fuel [FRAM G8164/ PUROLATOR F45057]


58884 [1] Kit, Transmission Filter [inc. trans pan gasket, filter, & filter gasket][WIX]
TF192 [1] Kit, Transmission Filter [inc. trans pan gasket, filter, & filter gasket][HASTINGS]
MD951858 [1] Washer, Transmission Drain Plug [crush-type]
[9] Fluid, Transmission, SP-III, 1QT / “Diamond”


==========================================================


ALTERNATOR SWAP
MD150657 [1] Alternator, 110A [A4T01493 / 12V] [3000GT VR4]
MD197470 [1] Alternator, 110A [A4T03191 / 12V] [3000GT VR4]
MD350609 [1] Alternator, 100A [A3TA1191A / 12V]
MD324756 [1] Alternator, 90A [3000GT]
MD354816 [1] Alternator, 90A [3000GT]
MD308882 [1] Pulley, Alternator Tensioner [36238] [GATES]



The top section [Timing Belt] parts have all been ordered today... RockAuto [RA] & eBay [just under $450, w/ the 5% RA promo].
The middle section was just done this past week by myself, along with NGK plugs/ wires, plus all new silicone vacuum/ coolant hoses [>$200].
The transmission service will follow the TB service... we're debating whether to do an Alternator upgrade.

We took a gamble on what most considered a turd... hell, I knew it was a turd.
But, with just under 111.000 original miles it has turned out to be a gamble where I left the table smiling.
We now have Montero G2.5's - in stereo - parked in the driveway... it's a sweet sound!


note; sorry if the list looks jumbled... I simply copied & pasted... tried to fix it, but I'm too old to get it right with computers...

 

[RyanY]

Despite the cooling system being clean as a whistle, I would recommend having the radiator rodded out at the same time as you're doing the rest of the cooling system maintenance. Doing it every time you change the timing belt is cheap insurance against overheating, which is the number one cause of head gasket failures.

 

[cr4x4cruiser]

Radiator maintenance...

I am in agreement, especially after attempting to clean this whole system out. The price of having a shop doing the radiator properly is a very small price to pay.

We'll be shopping around for a shop in the coming days.

Thanks for reminding me of the obvious [for which I completely put out of mind].

- Wm.

 

[quailchaser]

Are you sure the SOHC engine is an interference engine? I always thought the DOHC was, but the SOHC was not.

 

[Marcus2113]

Are you sure the SOHC engine is an interference engine? I always thought the DOHC was, but the SOHC was not.

Yes, to my knowledge. I also did a quick search to research and confirmed it as well.

From my understanding, the DOHC is not only an interference engine, but also had a butterfly valve issue if not properly maintained, which would also severely damage the engine.

-Mark

 

[quailchaser]

The butterfly valve issue must have been what I was thinking of. Thanks for the clarification.

 

[cr4x4cruiser]

Toasty created this thread;

'Anyone care to help categorize Monteros?'

http://forum.expeditionportal.com/archive/index.php/t-141231.html

Plenty of information to break down the differences in each particular model/ year... it should be a "sticky" [please take note, powers that be]!



To be specific, the 3.5L that is the bane of everyone's existence is the 6G74 DOHC.

Only the Double Overhead Cam design has a crippling design defect, 6G74 SOHC engines do not have this design flaw [1997/ up].

Basically, there is a "butterfly" assembly built into the lower plenum... when [not if] any of it fails the metal bits and pieces get sucked into the engine, rendering it a boat anchor.

It would appear that this primarily occurs when under load [when you need it most] - like accelerating up hill/ away from a light/ overtaking.

One/ more of the [7] bushings will fail - leading to destruction.

you will find it in Montero's from model years 1994 through 1996 [not before, not after].

Not ALL Montero's came with this engine in these model years... some also had the 3.0L.

Per Toasty's records; V45 6G74 3497 P-24V DOHC 3.5P LWB 07/93-04/97



You can find plenty of tutorials dealing with the destruction of these engines, due to the defect... as well, you will find plenty of repairs done as a result.

Key name/ part numbers to consider;

TANK, ENG. AIR INTAKE SURGE [Mitsubishi nomenclature]

INLET, MANIFOLD [what most everyone else calls it]

MD313333 VACV48-001, 5109 [Old Part #]

MD335940 VACV48-002, 9512 [New Part #]



Discussions;

https://www2.pajeroclub.com.au/forum/showthread.php?t=25792

http://4x4wire.com/forums/ubbthreads.php/topics/362354/2.html


"... The warning signs for this problem are:

A] Rattling from front of engine.
Check using the screwdriver stethoscope method at the front uppermost part of the plenum.
If suspected, look for the lever where the vacuum servo attaches to the butterfly valve shaft and press a screwdriver against this lever.
The rattling should stop.

B] Hissing noise from same area as above.
Only the front plastic bushing is "unsealed" so when this wears unmetered/unfiltered air will be sucked in.
The rearmost bushing is sealed with a metal cap pressed into the plenum casting.

C] Possible engine vibration at around 3000rpm.
Diminishes at about 3200rpm..."


If your rig has this engine we hope you take extreme caution, and make sure all is in order...


- Wm.

 

[RyanY]

That post is exaggerating the problem considerably - you fix or replace the lower plenum once and it's no longer an issue, much the same as the crankshaft bolt. It's something to keep in mind but definitely not "the bane of everyone's existence".

 

[cr4x4cruiser]

We shall disagree... it is an absolute design defect.

It is a catastrophic event when it occurs... no less so than breaking a timing belt and the inherent damage it wreaks, upon interference engines.

I know of no one that would select any year Montero with this engine, when others w/o the defect may be around.

Yes, it can be dealt with - as can a timing belt.

However, this issue by itself, ups the cost/ time expended/ effort required as compared to most other Monteros... especially so when one is inclined to hire out such jobs.

This is a serious caveat for most anyone pondering a Montero in their future.

Those over the years that have suffered such a failure with this particular engine, the globe over, would likely agree that it was/ is the bane of their existence [at least when applied to vehicles in their garage].

Too dramatic... possibly/ probably.

Overstated... I don't think so.