Hello, I have a 1999 Nissan Maxima with 150k miles. Recently I've been having trouble with it having almost no power and overheating. I've replaced the fuel filter and crank sensor. The coolant resaviour is full and not leaking. I have also replaced the radiator fan about 10k miles ago. I think it might be the spark plugs or the coil packs as those are known to go out on these vehicles. I was wondering if anyone had any insight as to what it may be. Thanks!

 

Are the fans for sure coming on?

 

Any Check Engine Lights or service Engine Soon Lights on?

Has the coolant ever been flushed in the 23+ years the car has been on the road? The reservoir full doesn't necessarily mean the entire system is full with no air in it.

There so many things that could cause symptoms like this. That's why the car has a system that tells you what's broken turning the above lights on.

 

Since you’re speculating that issues with either spark plugs or coil-packs may be the cause(s) of overheating, I’m curious as to what it is exactly that you’re considering ‘overheating’.

 

Most of the things you've listed have nothing to do with overheating, and since that's the more pressing issue, let's focus on that first.

How are you determining the car is overheating, just the gauge on the dash? Do you have any more detailed info from the OBD2 port or Nissan com port? Under what circumstances does the car overheat? Has the thermostat ever been replaced?

 

"overheating and low power"?

What about the head gasket??

 

I assume that your temperature guage is pegged on hot. Also that the symptoms are worst on a hot day, when driving up a long hill, or stuck in traffic.

Is that correct.

Spark plugs have little to do with overheating.

A malfunctioning cooling system is the cause.

Your car probably started overheating because it's almost summer now. The days are hotter.
Cause and effect related.

Suspects

Low coolant level
plugged radiator
fans don't turn on
defective thermostat.

all those can be replaced for a reasonable cost.

please tell us exactly how and when your car overhears.
Is it worst on a hot day.

Check and report if your fans are on while the engine is on and running hot.
Also touch the top of your radiator. It should be hot.
if it's not, suspect bad thermostat


Please remove the radiator cap first thing in the morning. Confirm that the radiator is full of coolant.
A small hole in the hose between the coolant reservoir and the radiator could stop flow to the radiator from the tank.

 

Please check the engine oil.
it should look like oil and not chocolate milkshake.

Also check the coolant in the radiator. It should not have oil in it.