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There's a thread below about the ECU being damaged when engine coolant leaks into the IACV stepper motor or the electric motor mounts on an automatic trans car. Is there a way to circumvent this from happening? Parts that can be replaced as preemptive maintenance to delay the onset of damage?
The thread I referenced doesn't say anything about that. Maybe you mean the thread it linked to that has the photo of the board? That thread does talk about disconnecting the motor mounts and maybe the transmission mount(s). OK, I'll need to look at all these things when the weather gets better. If you bypass the IACV, does the ECU throw a code? Also, isn't the IACV just a solenoid? Has it been proven that leaking coolant is really the cause? No car with the IACV bypassed ever has this issue again? Just wondering, cuz it seems unlikely to me that coolant would have a lower resistance than the windings on a solenoid. Maybe there's control circuitry in the IACV module that gets hosed by the coolant...
The thread I referenced doesn't say anything about that. Maybe you mean the thread it linked to that has the photo of the board? That thread does talk about disconnecting the motor mounts and maybe the transmission mount(s). OK, I'll need to look at all these things when the weather gets better. If you bypass the IACV, does the ECU throw a code? Also, isn't the IACV just a solenoid? Has it been proven that leaking coolant is really the cause? No car with the IACV bypassed ever has this issue again? Just wondering, cuz it seems unlikely to me that coolant would have a lower resistance than the windings on a solenoid. Maybe there's control circuitry in the IACV module that gets hosed by the coolant...
sheesh, it's pretty easy to find with a search. covered multiple times in many threads- but here you go,
for your other questions:
1. no codes
2. iacv is a stepper motor, im guessing fancier than a solenoid
3. not sure how to prove it exactly- i suppose you could take the gasket off and let it flood with coolant to see if it fries you or not. doesn't seem worthwhile to me but if you want to test it out please let us know what you find
4. i don't recall coming across anyone on the forum who had this return after the bypass
In the most very basic sense, the IACV is a solenoid. But even then, not really. A solenoid is electric wire wound around an iron core (an electromagnet) to produce a magnetic field that moves a plunger or something back and forth. A motor has electromagnetic coils but no plunger. The electromagnetic field makes a part rotate (the armature). The IACV is an electric motor that has 4 electromagnetic coils in it. These coils do not make the armature spin constantly, the coils are used to make the armature move a small percentage (a few degrees) of a revolution. This is called a stepper motor. The amount of time that the current flows in the coils determines how big or small of a step the armature turns. In order to accomplish a step, one coil will start the armature turning while another coil will stop it.
Originally Posted by jackman
Has it been proven that leaking coolant is really the cause? No car with the IACV bypassed ever has this issue again? Just wondering,
There is no solid proof of this, but the theory is solid for any older, original IACVs. Also in theory, the windings in the IACV should not short out even if the antifreeze did leak into the stepper motor chamber and flood it.
There is no argument that antifreeze leaks into the IACV stepper motor. So what about the theory that the coolant shouldn't cause a short? It is a good solid theory that works.
What very few people know about is that Nissan studied this problem and there was a 2nd factor involved. The insulation on the electromagnetic wire was substandard and did not meet the specifications that Nissan set. If you have ever looked at a motor, the insulation is not plastic, it is like a varnish. Over time and we're talking 10 to 15 years, the insulation would crack and fall off the wire, allowing the antifreeze coolant to contact bare wires and... POOF. I suppose the failing insulation would cause the motor windings to short out after a really, really long time.
I got this info from a Nissan report on the IACVs failing. What makes me mad is that I can't find it. I evidently lost it.
So if your IACV ever shorts out, the new ones won't have the bad insulation and should be immune to a coolant leak. And even if it does, will you still have this car in 2030?
Originally Posted by jackman
it seems unlikely to me that coolant would have a lower resistance than the windings on a solenoid. Maybe there's control circuitry in the IACV module that gets hosed by the coolant...
Unfortunately this assumption is incorrect. If you were using truely pure water, you would be correct. Pure water does not conduct electricity. It is the impurities in the water that allow electricity to flow. Let's review basic physics. Electricity needs molecules that have free electrons in order to flow through the material. The water molecule, H2O, is a stable molecule with no free electrons. So water with no impurities in it means no electrical flow. The antifreeze equates to impurities in the water.
Working in conjunction with this is that the antifreeze is creating a short between the bare wires of the stepper motor windings. Have you ever unraveled the wire off of a motor armature or a solenoid? That's one long a$$ wire. Wire does have resistance and the longer the wire, the greater the resistance. Have you ever been following the FSM and troubleshooting some electrical circuit and the FSM says to measure the resistance of some solenoid? The FSM might say the resistance should be 10 ohms. This is enough resistance to prevent a short circuit. In the case of the IACV, the FSM says the resistance of the stepper motor windings should be 22 ohms. So the antifreeze shorts the wire windings to one another, creating a very short wire with very little to no resistance and... POOF.
Over time and we're talking 10 to 15 years, the insulation would crack and fall off the wire, allowing the antifreeze coolant to contact bare wires and... POOF. I suppose the failing insulation would cause the motor windings to short out after a really, really long time.
So if your IACV ever shorts out, the new ones won't have the bad insulation and should be immune to a coolant leak. And even if it does, will you still have this car in 2030?
I intend to have my '00 until at least 2022 or beyond. I just passed 175k on the original IACV so I guess I got lucky so far.
I intend to do the coolant bypass thing in the coming days, but are you saying that no matter what, the poor insulation is partly to blame? So it will still possibly fail?
So to truly prevent the issues, should I purchase an updated IACV? And where would I do so?
Thx
The insulation on the electromagnetic wire was substandard and did not meet the specifications that Nissan set. If you have ever looked at a motor, the insulation is not plastic, it is like a varnish. Over time and we're talking 10 to 15 years, the insulation would crack and fall off the wire, allowing the antifreeze coolant to contact bare wires and... POOF.
Well then, I'm betting the wires short with or without coolant once the insulation fails. That's the usual failure mode for steppers and solenoids - shorted windings. The "varnish" you're referring to is called enamel, and there are various grades depending on intended use. Some of it is absolute garbage, some will last a hundred years. In this case, coolant might aggravate the problem, but as you say (and as Nissan apparently discovered), the real problem is substandard insulation.
This means the only 100% sure solution is to replace the IACV, and I guess it needs to come from Nissan.
EDIT: Rock Auto sells the Hitachi ABV0039, which they say is the OEM part for a 2000 Max, for roughly $119. Can it be assumed that all the OE IACVs that would be in stock now have been upgraded to resolve this problem?
EDIT: Rock Auto sells the Hitachi ABV0039, which they say is the OEM part for a 2000 Max, for roughly $119. Can it be assumed that all the OE IACVs that would be in stock now have been upgraded to resolve this problem?
Hitachi is a great name in automotive electronics and manufactures many OE parts. I'd trust anything with their name on it.
If you're planning on swapping the IACV make sure you have the proper screwdriver. The screws are very tight and seem to be made of a very soft metal. A screwdriver that's "close enough" will strip the heads in a heartbeat.
For what it's worth, the IACV in my 00 went 300,000 miles without failure. I swapped it when I came across a 00 in the salvage yard that someone had been "throwing parts" at to get running. It had a brand new Hitachi IACV which I took along with a new MAF and some other spare electronic parts.
There's a thread below about the ECU being damaged when engine coolant leaks into the IACV stepper motor or the electric motor mounts on an automatic trans car. Is there a way to circumvent this from happening? Parts that can be replaced as preemptive maintenance to delay the onset of damage?
I am a new member and I have a 1998 Maxima 2L from 2012 July the car start stalling when the weather is hot and I have to wait for about 5 minutes and it will start will stall when I stop again. I thought it is the alarm`s immobilizer system and had it changed but after 4 weeks the problem started again somebody said it is a relay which get hot and start when cool again. I noticed sometimes after 1 minute I started car if the radiator fan comes on the car is going to stall can anybody help me solve this problem?
I am a new member and I have a 1998 Maxima 2L from 2012 July the car start stalling when the weather is hot and I have to wait for about 5 minutes and it will start will stall when I stop again. I thought it is the alarm`s immobilizer system and had it changed but after 4 weeks the problem started again somebody said it is a relay which get hot and start when cool again. I noticed sometimes after 1 minute I started car if the radiator fan comes on the car is going to stall can anybody help me solve this problem?
Here's my question, how does simply having a worn motor mount fry an ECU? I understand that unplugging it will not let it send info anywhere, but how does it being simply worn out fry something?
Here's my question, how does simply having a worn motor mount fry an ECU? I understand that unplugging it will not let it send info anywhere, but how does it being simply worn out fry something?
In a nutshell: It's not about sending information anywhere. It's about basic Ohm's law, and what happens when resistance of the electronic mount drops below expected boundaries.
In more details: In this context, "worn out" means "worn out, electronically".
The ECU controls the stiffness of the mount by applying electrical current to the dielectric solution liquid within the mount. If for some reason, the resistance of this solution/component becomes zero (or something close to it), the current becomes very large and fries the ECU. This happens because Nissan engineers did not protect the ECU from this event - whether it's by design, or by carelessness - is a mute point at this time.
In a nutshell: It's not about sending information anywhere. It's about basic Ohm's law, and what happens when resistance of the electronic mount drops below expected boundaries.
In more details: In this context, "worn out" means "worn out, electronically".
The ECU controls the stiffness of the mount by applying electrical current to the dielectric solution liquid within the mount. If for some reason, the resistance of this solution/component becomes zero (or something close to it), the current becomes very large and fries the ECU. This happens because Nissan engineers did not protect the ECU from this event - whether it's by design, or by carelessness - is a mute point at this time.
Ohhhh, I see now. I thought by worn out it meant simply just old and the rubber was torn. That still seems odd to me, but it any case, I'll unplug my front one today. I can visibly see that it's cracked, but I'll still unplug it when the engine is over 1000rpm.
The ECU controls the stiffness of the mount by applying electrical current to the dielectric solution liquid within the mount. If for some reason, the resistance of this solution/component becomes zero (or something close to it), the current becomes very large and fries the ECU. This happens because Nissan engineers did not protect the ECU from this event - whether it's by design, or by carelessness - is a mute point at this time.
I'm sorry, but I have to disagree with you. This is not how the electric motor mounts on the 5th gen work. One can only dream of it being that sophisticated. There is no dielectric solution with current flowing through it.
The electric motor mount uses hydraulic pressure to achieve the level of firmness. The mount uses a small oil pump operated by an electric motor.
The problem is that the motor is a cheap piece of dog doo that fails in various ways and creates a short
This is a view of the bottom of the motor mount. The "bulge" is the electric motor.
This is the motor removed from the mount. It shows the drive tang that goes into the oil pump.
This is a view of the bottom of the motor mount with the electric motor removed. You can see the oil pump connection.
This is a view of the motor mount from the side with the vinyl wall removed. Inside you can see a metal plate surrounded by ivory colored plastic. This is the oil pump and reservoir unit.
I stand corrected, and as usual, Dennis is right. (I made a conjecture based on my other knowledge/experience, and should have probably say that .... ).
Seeing your pictures, I am not surprised these pumps fail.
Well I must be stupid or something because I cannot figure out how to unplug the motor mount connector. I tried everything and couldn't get it unplugged. I'm debating whether or not to cut it.
Well I must be stupid or something because I cannot figure out how to unplug the motor mount connector. I tried everything and couldn't get it unplugged. I'm debating whether or not to cut it.
Here's a pic of the harness side. Just push down the tab and pull. It doesn't slide in and click like most of the others on these cars. You may have to push it with something because the fins on either side of the tab make it hard to do with your fingers. I seem to remember these being very tight.
Here's a pic of the harness side. Just push down the tab and pull. It doesn't slide in and click like most of the others on these cars. You may have to push it with something because the fins on either side of the tab make it hard to do with your fingers. I seem to remember these being very tight.
Does this mean it won't matter what RPM the motor is at when the mount is disconnected? It will return to the soft setting when the pump stops?
Anyone?
Someone said earlier that if the vehicle is turned off with the motor mounts in a certain mode, they'll stay there. But that was it had also been suggested that the mode change is by means of solenoids. If the mounts are actually pumped up hydraulically, does it matter? Won't they go to the soft setting as soon as the pump is powered down (or at least bleed down over some period of time)?
Someone said earlier that if the vehicle is turned off with the motor mounts in a certain mode, they'll stay there. But that was it had also been suggested that the mode change is by means of solenoids. If the mounts are actually pumped up hydraulically, does it matter? Won't they go to the soft setting as soon as the pump is powered down (or at least bleed down over some period of time)?
Unplugging it when it's in its hard phase, it will stay like that until you plug it back in. It just means the hydraulic pump thing will be up the whole time. Think of it like a window. If you leave the window up and unplug it, it will remain up until you plug it back in and put it back down. Once the motor mount is unplugged, it's staying in whatever position it's in.
Well I must be stupid or something because I cannot figure out how to unplug the motor mount connector. I tried everything and couldn't get it unplugged. I'm debating whether or not to cut it.
you can cut from the mount side . If you ever want to get new electric mounts the wire will still be in tact.
I found out 5 years after buying my maxima that one was cut and another disconnected the whole time!
Can I rev the engine to 1500 and turn off the key?
No, because when you shut the car off, the RPM's are still gonna come down. The PCM will realize this. Just do it when you start the car for the first time in the morning. If you live anywhere where it's cold out, first start of the day and it will idle over 1000rpm for a good five minutes if you let it heat up on its own. Unplug it then.
On a different note, I know my front motor mount is trashed because 1. I can see it, and 2. I get a clunk whenever I let off the gas and give it gas again on the highway. Also if I give gas too much from a dead stop, it will clunk too.
Anyway, I watched videos on replacing it, but was disappointed to find that they all said remove the radiator or cooling fans, which still requires to pull the upper hose. I hate coolant, but it looks like I can replace it without undoing anything. Hopefully I'll be able to do this job in the summer.
On a different note, I know my front motor mount is trashed because 1. I can see it, and 2. I get a clunk whenever I let off the gas and give it gas again on the highway. Also if I give gas too much from a dead stop, it will clunk too.
Anyway, I watched videos on replacing it, but was disappointed to find that they all said remove the radiator or cooling fans, which still requires to pull the upper hose. I hate coolant, but it looks like I can replace it without undoing anything. Hopefully I'll be able to do this job in the summer.
you mean a bump? I get that too but thought it couldve been related to the TSB associated with the Solenoids in the transmission
I began to think it may be because of the mount not functioning properly
No, because when you shut the car off, the RPM's are still gonna come down. The PCM will realize this.
There's no way I'm gonna crawl under this and wrangle with those plugs while the engine is running. Is there any reason not to pull the 15A fuse that powers the mounts? If that's done with the engine above 1,000 RPM, the ECM can't change the setting. Then the plugs can be worked free as time permits.
There's no way I'm gonna crawl under this and wrangle with those plugs while the engine is running. Is there any reason not to pull the 15A fuse that powers the mounts? If that's done with the engine above 1,000 RPM, the ECM can't change the setting. Then the plugs can be worked free as time permits.
You should try (pulling the 15A fuse) - and if/when you do, let us know how it works out!
I have a more substantial question about this whole thing: If we assume that disconnecting the engine mount while (RPMs > 1000) keeps the mounts hard, then there must be something - let's call it a "valve" - that prevents the pressure from dissipating when power is removed. What/where is it? And how does it prevent "pressure" leakage after power to the mount has been removed?
There's no way I'm gonna crawl under this and wrangle with those plugs while the engine is running. Is there any reason not to pull the 15A fuse that powers the mounts? If that's done with the engine above 1,000 RPM, the ECM can't change the setting. Then the plugs can be worked free as time permits.
I don't know if you have 2 or 1, but unplug it before you start the car so that it's somewhat loose, and then when the car is running, unplug it. I did it this way and I'm still here to talk about it. Radiator fans are not gonna be running if it's the first start of the day. Cut the rear one if you have it.
I don't know if you have 2 or 1, but unplug it before you start the car so that it's somewhat loose, and then when the car is running, unplug it. I did it this way and I'm still here to talk about it. Radiator fans are not gonna be running if it's the first start of the day. Cut the rear one if you have it.
But the question is - why bother?? Pull the fuse when the mounts are in the firm position, then just leave it out forever. That's the same as disconnecting everything. Screw the plugs. Leave 'em on.
But the question is - why bother?? Pull the fuse when the mounts are in the firm position, then just leave it out forever. That's the same as disconnecting everything. Screw the plugs. Leave 'em on.
That won't work because there are other things on this fuse.
re: Disconnecting the mounts in "firm" mode - does this really make a long term difference?
If the mounts use hydraulic pressure to firm up, for them to stay firm they would have to maintain that pressure. Is it reasonable for a closed hydraulic system to maintain pressure for months/years? Surely the pressure must slowly drop over time and the mount lose its "firmness".
You are probably right that the oil pressure would leak out over time. I guess this leaves you with 3 choices -
1) do nothing
2) replace the mount
3 re-connect the wires every couple of months.
That won't work because there are other things on this fuse.
Thanks, I do see that connection off to the left of the schematic now that you mention it. OK, I'll probably just pull the plugs and not worry about which setting the mounts are on.
you mean a bump? I get that too but thought it couldve been related to the TSB associated with the Solenoids in the transmission
I began to think it may be because of the mount not functioning properly
Is it possible this is from my deteriorating trans mount that looks cracked and broken? I'm seeing about an inch space at the bottom.
Would this cause a "bump"?
01-11-2017, 01:29 PM
