Montero Gen 2 Spark Plug Change - 3.5L V6

Conk

New member
Hi All,

I just recently purchased a 1995 Montero SR (see attached pic). It's was a single owner vehicle with 150K miles. Not sure when the spark plugs and wires were last changed so I plan on doing it myself. I've done some research on this and understand that I have to remove the intake plenum. I have the factory service manual and also found the following guide on 4X4 wire that should be helpful: http://www.4x4wire.com/mitsubishi/tech/lower_plenum/. Is there anything else I should change while doing this job? Any tips on how to do this? Was planning on using NGK wires and Iridium plugs. Thanks, Dave
 

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Toasty

Looking for that thing i just had in my hand...
If i were you i'd do the complete timing job along with water pump, pipe o-rings, cam and crank seals and a new crank bolt.

However just the tune up i'd do the crank case vent while you're in there, it's also under the manifold. Inspect the condition of the butterfly valves, make sure nothing is loose.
 

RyanY

Adventurer
There are 3 small coolant bypass hoses behind the thermostat housing that are impossible to get to without removing the plenum, and are most likely still original. When they start to leak they usually go unnoticed because the leaking coolant runs into the valley between the cylinder banks and evaporates, never leaving any visible signs. I'd get 2' of silicone hose (1/4" I believe) and replace them while the plenum is off.

It wouldn't be a horrible idea to replace the valve cover gaskets and spark plug tube seals while you're in there either.
 

MrGalantguy

Mitsubishi Loyalist
If you can..replace every single top end gasket and O-ring while you do the spark plug change as you don't want to remove all those pieces again to replace something like a crossover pipe o ring.
 

coffeegoat

Adventurer
In case you haven't figured it out yet, replacing the spark plugs is a bit of a pain - you have to remove a bunch of stuff. And since the rig is new to you, if you don't have any service records it's worth considering how much you want to spend for piece of mind. You can "just replace the spark plugs," or you can do an entire top end refresh like Ryan, Toasty, and MrGalantGuy mention. Spark plugs are cheap, a full refresh - timing, gaskets, water pump, seals, etc etc etc, can easily reach over $1k - but afterwards you'll feel like you have a really great handle on all of the likely failure points for a 20+ year old rig. Furthermore, the work to replace all that other crap is actually pretty minimal over and above what it's going to take to replace the spark plugs. Mostly, you need to think carefully about how much your time is worth, how much you want to spend, and what would be worst case if the truck went down unexpectedly. Most of these parts aren't easily available at your local auto parts shop, so if you run into something it might be a week or two until you're up and running. I just ran into the ABS failure issue on Gen III's, it'll be at least a week until I have all the parts in hand and the time to fix it which means the truck is undriveable during that time - and that sucks.
 

The Viper

Adventurer
Im just gonna add...the plenum does NOT have to come off to change the spark plugs on a 95 dohc sr...but it sounds like it might be good to do some other things while the plenum is off :)
 

IncorpoRatedX

Explorer
Welcome to the forum Dave, it was nice talking to you earlier this week, glad to see you made it here and the ADD forum.

This escalated quickly! I will say the plenum can stay on, but everything else around it has to come off, on the quad cam you can snake the plugs out without removing the manifold, but, you're pretty deep at that point and it's a pain to snake them around the driver side of the manifold. I've had concerns while doing changes with the manifold on about getting the plugs in straight, never cross threaded any, but it was a concern.

A good eye, patience and a thorough check goes a long way, inspect the valley below, the hoses and the gaskets, look for leaking and seeping and make the call from there, if you're trying to reduce how deep you have to go.
 
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