Author Topic: Let's do the flashing front lights thing.  (Read 409 times)

Shovel

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Let's do the flashing front lights thing.
« on: March 26, 2019, 10:36:55 AM »
OK I get it, you're new to Monteros, you just got one and it has a problem where the lights representing the front wheels in your dash are flashing and you want help on it, and all the old timers are like "THIS again???"

It does get discussed an awful lot.. like.. an AWFUL awful lot so if you stick around a while you'll get sick to death of it too.

But for now, you're new and it's not your fault, let's get this shit fixed.

It's pretty simple and it's pretty cheap if you hop to it and fix it before it does real damage..  think of it like a quick test of whether or not you should own a quarter century old 4x4 - if this is too much for you, sell it.   It only gets harder from here.    Tough love.

Let's do a quick rundown of how the 4wd system works on your Gen2 or 2.5 Montero:

  • The transfer case lever itself physically moves gears around inside the transfer case.   It's not like a pushbutton or a rotary knob that tells a computer to ask a servo to move a thing, dig?   When you move the lever on the other end of that lever is a set of splines you're positively engaging and that's why you have to be stopped and in neutral to switch into and out of low range.  If you manhandle the lever you're fucking those splines up. 
  • If your transfer case lever is loose and doesn't cleanly and positively engage, your fulcrum ball has disintegrated.   Common problem.  Do not force it,  do NOT force it.  Do not force it.   Please do not force it.   After you're done NOT forcing it,  do NOT remove the three nuts immediately close to the fulcrum ball because there is a bolt on the other side that will fall down into your transfer case and then you get to try to get it out of there which is a lot less fun than it sounds.    Search around for instructions on this.
  • In addition to the transfer case lever you move with your hand to engage the front driveshaft there is also a vacuum operated spline engagement in the front axle, often called the CAD or "Center Axle Disconnect" - this exists because without it your front driveshaft and the bottom of the transfer case would always be spinning in 2wd, which is a waste of energy and wear and vibration and noise.
  • The default state of the center axle disconnect is locked,  as in 4wd.   When your engine is off and there is no vacuum to the CAD, the axle engages like as if you're in 4wd.    When you start the engine in 2wd vacuum from the engine is supposed to be routed to the diaphragm (located on the rear of the front axle tube) and pull the CAD out of engagement
  • Almost all of this system is ANALOG (switches, wires, solenoids..) and must be troubleshot using first principles and direct observation

So how does one troubleshoot the CAD?   I'm glad you asked. 

The following assumes your shift fulcrum ball is not disintegrated and further assumes you have some aptitude at working on vehicles, know to properly use jackstands and wheel chocks and keep your floppy bits out of moving parts,  etc...  if working on cars is all new to you,  uhh.. just be careful and don't blame the internet if you hurt yourself. 

  • Get under your Montero and remove the skidplate under the engine.  At the rear of the front axle tube you'll see a rubber accordion sleeve thing and a vacuum diaphagm.   That's the actuator for the CAD
  • Clean everything down here thoroughly.  A clean vehicle is infinitely easier to work on.   Scrubbing bubbles, degreaser, pressure washer,  whatever... get it clean down here it's worth it.
  • Observing necessary safety practices,  make sure the transfer case lever is in 2wd and the transmission is in neutral and have a competent partner prepare to start the vehicle.  Under the vehicle, pull back the rubber accordion thing and observe the metal rod under it and have your partner start the vehicle.   You should see the metal rod move a little. This indicates that the 4WD system has commanded the solenoids open and that the vacuum diaphragm is pulling as instructed
  • If the metal rod thing did not move,  or if it only twitched a tiny bit you may have a fault upstream from there.  Return the rubber accordion thing and pull the vacuum hose off the end of the vacuum diaphragm and check it for vacuum.    If it has vacuum then a small possibility exists that your diaphragm is  faulty - it can be removed and inspected off-vehicle if everything else checks out.  You can also use a hand operated vacuum pump on the diaphragm to see if it has a leak. Replacement diaphragm assemblies are available and affordable. 
  • If there is no (or very little) vacuum at the diaphragm, work backward from there.   You'll observe a vacuum canister and a bunch of noodly vaccum lines - if they're questionable at all just replace them - it's cheap, your vehicle is a quarter century old.. it's not a waste of money to replace them.   It's a waste of money to have a vehicle you're not able to use because you didn't take care of it.   Replace them one at a time so you don't get them mixed up.
  • Upstream (vacuum wise) from the diaphragm and vacuum canister is a pair of solenoids.   Aside from vacuum leaks these are kind of the most common point of failure for this diagnosis..  locate the vacuum line upstream of these and inspect it for vacuum (engine running, transfer case in 2wd) - if there is vacuum present there it's possible the solenoids are faulty but it's also possible the switches on your transfer case are not sending voltage to the solenoids.   You can choose to just replace the solenoids and see what happens (about $20...)  or troubleshoot why they're not working by using a multimeter and the electrical diagrams in the back of your FSM.   
  • If there is little or no vacuum upstream from the solenoids, you probably have a vacuum leak.    The vacuum source from the solenoids goes a short distance to a metal tube along the firewall and then the other end of that metal tube is on the driver side of the vehicle (left hand drive) - for 97-00 SOHC that's a little 6" long vacuum tube that connects to the top of the intake manifold near the firewall.  Inspect that for leaks, and also check every other tube on your intake manifold for vacuum leaks.   They're all decades old and probably all need replacing.. inspect them well and replace as necessary
  • Electrical troubleshooting for the solenoid action requires wiring diagrams which are available in the FSM, that you can either buy on ebay or download for free from www.mitsubishilinks.com .
  • If this all goes over your head or you don't want to work on it - that's cool too,  just print out this topic and bring it to your mechanic and they should be able to follow along.
  • After you're done with all this, you will definitely want to change your front diff oil.   Why? Because if the CAD has been in a state of partial engagement it will have been grinding on itself and slowly turning itself into confetti.   That confetti goes into the diff oil and wears on the gear surfaces, bearings,  everything in there.   Not what you want.  Inspect the oil as it drains out and if there is glitter in it already you will want to make a decision about whether to just flush it a few times and hope for the best, or rebuild it with new bearings or replace it with something else (like 4.90s..)

OK so what if you put off fixing this?  That's OK?   No.. not really.   Look it's your vehicle if you want to neglect it that's on you... and if it fails from your neglect that's on you.   You're a grown up.     The deal is that when the vacuum solenoids are failing or a vacuum leak causes the CAD to partially fail during low vacuum circumstances (heavy throttle... climbing hills in 2wd)  it allows the splined CAD sleeve to slide over into itself and start grinding the splines on the axle shaft or stub shaft.   Grinding isn't good for them, they wear themselves out and the shavings from that grind go right into your front diff oil where they get into the bearings and the ring & pinion.. greatly accelerating heat and wear on those as well.   It's all not good.    You'll want to fix this sooner than later and apart from  your own time,  replacing everything is like $60 bucks if you catch it early (vacuum solenoids,  diaphragm/actuator and vacuum hoses) .. as opposed to many hundreds if you end up ruining the whole front axle.   

« Last Edit: March 26, 2019, 02:37:15 PM by Shovel »

TOASTY

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Re: Let's do the flashing front lights thing.
« Reply #1 on: March 27, 2019, 07:06:09 AM »
 Another solid gold post.

Hooots

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Re: Let's do the flashing front lights thing.
« Reply #2 on: March 27, 2019, 12:18:07 PM »
Ok.....so.......ever since Ernest swapped out my gears and put manual hubs the lights have ALWAYS flashed on my '97SR, but he told me it was fine and that everything was ok. I'm not educated enough to recall why the lights were always flashing but.......I'll give him call to see

ON another note. A few weeks back it would engage into 4wd just fine.......but when i went from 4H to 2wd it kept wanting to 'pop' back into 4.......is this a 'symptom' of busted fulcrum ball?
"AZPAJERO" - 1997 Gen 2 Montero SR, 5.29 gears, 37" tires, Detroit front locker, Factory rear

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GrantCee

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Re: Let's do the flashing front lights thing.
« Reply #3 on: March 27, 2019, 02:28:54 PM »
think of it like a quick test of whether or not you should own a quarter century old 4x4 - if this is too much for you, sell it. It only gets harder from here.

Truth.

This should be required reading for everyone who wants to buy a used Montero, regardless of model.

Shovel

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Re: Let's do the flashing front lights thing.
« Reply #4 on: March 27, 2019, 03:18:41 PM »
Ok.....so.......ever since Ernest swapped out my gears and put manual hubs the lights have ALWAYS flashed on my '97SR, but he told me it was fine and that everything was ok. I'm not educated enough to recall why the lights were always flashing but.......I'll give him call to see

If he used a one piece axle from an AWD sport or otherwise eliminated the CAD, then the wiring needs to be updated.  I posted a how-to in this forum.  Takes a 5 pin relay and a little wiring to permanently solve.

Funtero

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Re: Let's do the flashing front lights thing.
« Reply #5 on: June 15, 2019, 09:30:05 PM »
This is the best write up I have ever seen on this system. Thanks you!