ZoonZakal

Hello, So my 99 maxima overheated today while driving. I pulled over and let it cool down, then checked my fluid levels. They were normal. I got it home and looked it over.
There are no visible leaks. I've had water pump problems on another maxima so I'm aware where to look to see if it's leaking water. It isn't. So I'm currently assuming it's not the water pump.
I went ahead and picked up a new thermostat and installed it. I raised the front of the car and let it idle for ~10 min (with the radiator cap off). No overheating. Put the cap on and drove it around the block and it started overheating again.

I let it set of a few hours and tried "burping" it again. Same thing. No overheating while the cap is off, but as soon (well about 30 sec) as I put it on and increase the throttle it starts to overheat.

So... any ideas on my next step? I plan on trying to see if it's still overheating in the morning after sitting all night, but I'm not very optimistic about it not.

Radiator looks great. No collapsed lines. No visible crude or damage to the fins. Oh if I increase the RPM to about 2200 during idle with the cap off, it boils the coolant up out of the lid for a few seconds then drops back to normal.

Thanks

CMax03

iTrader: (3)

Fans working?

ThaMax

iTrader: (2)

To assist with troubleshooting, check out this thread and also check out post# 17 while you're in there

The Wizard

iTrader: (43)

If you have a scanguage or a scanner that can read live data, you can see if it's really overheating. Could just be the temp sensor next to the engine coolant temperature sensor that's acting up and giving bad information to the gauge cluster. Maybe it's even the engine coolant temp sensor? Not sure. I believe you can test for voltage or ohms on these sensors too for functionality. Their specs are listed in the FSM, which can be downloaded for free in my signature.

Just a total guess here, but would a clogged heater core cause this?

Did you install an OEM thermostat, or aftermarket?

Clogged radiator?

Was the heater on full blast while you burped the system?

Feel both radiator hoses as it over heats. If one is boiling hot and the other is cool to the touch or just warm (not hot), then your thermostat isn't opening.

asand1

iTrader: (1)

Water pump doesn't have to leak to be bad.

Finkle

Hot Damn!,
were the fins stuck in the engine?

ZoonZakal

Ya, both fans are going strong.

I have access to a live scanner. I'll have my friend bring it over today to test with it.

Aftermarket thermostat replaced. When it gets to overheating, the line that connects to the thermostat gets warm but not boiling hot like the other hose coming from the radiator. So it could just be a bad replacement thermostat?

The heater was on full blast while I burped the system. And the heater is working like it normally does.

I have to go to work now. I'll check out that other post TheMax as soon as I get off. Short shift only 3 hrs. So I'll be back soon to put my time into it.

Thanks guys

ZoonZakal

Ok, so thinking about it, I know that it's getting hot. It will start to boil the coolant if I bring the engine to 2000 rpm for 30 sec with the cap off. So I doubt it's a failing temp sensor.

I understand it could be a failing water pump. I'm actually currently working on a 95 that I know has a bad water pump. and it's .... I'll probably be starting a thread on that currently failing operation here soon. So, if it ends up being the water pump that's bad in this car. I'm ready to make it happen (or try), I'd just like to rule out other likely causes.

Flushing the system sounds like fun. I had to drain the radiator to replace the thermostat but have yet to flush the actual engine. Anyone have any advice on the best way to do this?

max-nutcase

well, these water pumps usually either leak when goin bad (and grind sometimes) or if someone didnt change the coolant or mixed right and the finns have rusted away....hows the coolant?..ive seen unmaintained max waterpumps that have literally rotted away to no fin at all

ZoonZakal

The coolant looks good. I picked up this car about 6 months ago, so I've no idea how it's been maintained. But the coolant that came out of the radiator when I changed the thermo yesterday looked brand new. It had no debris or anything visible in it. Put it back in afterwards.

CMax03

iTrader: (3)

Remove the thermostat and see if it still overheats! Apparently you have a clogged radiator or defective pump! You also could have a defective radiator cap!

max-nutcase

i had a 3rd gen yrs ago and took the T stat out.....i had all that coolant boiling...but i was bringin it to the jy soon and was torturing it