AT Temp/Battery/Brake Light and overheating

[cjsmith0703]

On my way home today and all 3 of those lights turned on. I didn’t notice anything odd at the moment. After continuing to drive just a couple more miles, the car begin to overheat. I checked the coolant and it still had coolant in the radiator. I filled it a few times to limp it home but it honestly wasn’t low when I checked the first time. Any idea as what’s going on? I know it could be alternator but that doesn’t really explain the overheating does it?

[mdmellott]

... the car begin to overheat. I checked the coolant and it still had coolant in the radiator. I filled it a few times to limp it home but it honestly wasn’t low when I checked the first time.

Your description is confusing. When you state that there was coolant in the radiator, are you actually referring to the coolant reservoir still having coolant in it? If the coolant was not low, why would you have to fill it, not just once but a few times, to get home? Is there any coolant dripping onto the ground from anywhere under the car?

[cjsmith0703]

Hey. Sorry for the confusion. I assumed it was low on coolant when it ran hot so I opened it while it was hot and lost a good bit of water. That’s why I filled it. It only took a little water though so it’s not overheating bc it’s lowing coolant

[mdmellott]

You have several seemingly unrelated issues going on. Using an OBD2 code reader, find out what diagnostic trouble codes have been flagged. Your alternator is not going to cause the issues you are seeing, except maybe for the battery light coming on. If your brakes are dragging, that could overwork the transmission and the engine and cause them both to overheat. Check that the fluid levels are correct in the transmission and the radiator when everything is cool. Your AT temp warning light coming on is a very serious warning as is the engine overheating. Check your radiator and A/C condenser fins to be sure they have good air flow and are not block by dirt, bugs, and debris. Check your cooling fan clutch to be sure it is operating when the engine gets hot. Do not drive any long distances until you have this figured out and fixed.

[cjsmith0703]

I only mentioned the alternator bc I saw multiple forums on here that had the same problem with the lights on that indicated the alternator was failing. Only issue was that none of them had the issue of overheating while still full on coolant

[mdmellott]

I only mentioned the alternator bc I saw multiple forums on here that had the same problem with the lights on that indicated the alternator was failing. Only issue was that none of them had the issue of overheating while still full on coolant

Good point. With all the actuators and other electronics in the transmission, I suppose something could go wrong there if your alternator was failing but I'm not sure. Test the voltage output at the battery terminals with the engine off. It should measure 12.6V if the battery was perfect. If it's less than 12V, the battery is either unable to hold a charge from the alternator or the alternator is not putting out enough current to charge it. Next, test the voltage output at the battery terminals with the engine running and everything else turned off. It should measure about 14V if the alternator is working well. If it measures closer to 13V there could be an issue with the alternator. Next, with the engine running, turn everything else on (A/C, blower on high, headlights on) and measure the voltage output at the battery terminals again. If it measures down around 12V, your alternator is not working well. Next, turn the A/C, blower, and headlights off and let the engine run for a few minutes. Turn the engine off then measure the voltage output at the battery terminals again to compare with the first measurement. The measurement should be the same or a bit higher. Measure it again a few hours latter to see if the voltage has dropped. If it has, the battery is either unable to maintain its charge or it's being drained by a short circuit. If that's the case either way, do this last test again by running the engine for 10 minutes or so to bring the battery charge back up but this time disconnect the cables for the battery terminals after you turn the engine off. Measure the voltage of the battery, as before to compare with the first measurement and then again after a few hours. If the voltage has dropped after a few hours, your battery is failing.

[cjsmith0703]

I had someone mention that it may be the belt since alternator indicator lights and coolant was full.

[mdmellott]

If the belt is loose, it could be slipping and not allowing the alternator to work well. If you have a QX4 with the 3.3L engine, the same belt drives the water pump so that would also be an issue if the belt is loose. On 3.5L engines the water pump is not operated by a belt.

[cjsmith0703]

Do you know if the belt should be around the alternator? It looks like there is a spot where the belt goes on front of alternator but the belt is not there. May not be the case but just looked like belt was supposed to go there. I’ll look when I get home today and do the battery test and the belt.

[mdmellott]

Check out the following link. It has two illustrations of the drive belt routing for a 2000 QX4. One for the 3.3L engines and one for the 3.5L engines. Either way, there should be a belt on the alternator pulley. Your car won't run for more 30 minutes or so without it, at which point your battery will be drained. Without that belt on a 3.5L engine, your fan pulley won't operate either. On the 3.3L engine your water pump and fan won't work. If you lost your belt, your issue and solution is obvious and an easy fix to replace the belt.
https://www.infinitipartsdeal.com/parts ... _belt.html

[cjsmith0703]

I’m not sure how to add photos on here but I went and checked based on that diagram and found my belt ripped to shreds. Had to cut what was left to remove it. I guess I will be putting on a new belt. That’s the serpentine belt that goes through alternator, right?

https://photos.app.goo.gl/XDZ6QRkVs5XQXw818

[mdmellott]

Yikes! I'm glad you made it home yesterday. Your battery is bound to be low now but hopefully with enough charge to start up the engine after you replace the belt. If not, you may have to get the battery charged or jump start your car. Let it run for awhile after you replace the belt so the battery charges back up. Don't bother with any of those tests for the voltage output of the battery and alternator until after you replace the belt. Even then, that may not be necessary.

[cjsmith0703]

Thanks for your insight. I just replaced radiator about 2 months ago so at first I was stumped as to what could be the issue. I thought about it at work today and felt it was the belt and that was confirmed when I got home this afternoon.

[mdmellott]

If all your belts are the same age or you're not sure, replace them all. Losing your power steering because of a broken belt while driving is dangerous.