car question
 

last night while driving home from lowes (which involves a pretty good drive up a hill: elevation difference ~1800 ft), i noticed that my engine temp was getting on the high side. It wasn't out of the band, but it was up on the edge.
This morning, I checked the radiator and it was full. However, the one odd thing I have noticed is that within the last 2 weeks or so, the heater sometimes just blows cold air. So when I need heat, I turn it on, then off, what a few minutes and try again for warm. Usually in 5 mins or so I get warm air.
Are the sensors/etc involved in both processes connected? Any ideas?

have you tried calling Car Talk?

is that the click and clack radio show?

yes it is. if you tell them about your leno appearance, I think you are more likely to get on the air.

thermostat? clog?
 

How old is the car and when is the last time you had your radiator flushed? Could be that your thermostat is not working (so the coolant water is circulating just within the engine) or there is a clog in your system due to deposit of scale/gunk/whatever. I once had a car where the engine temp was plenty warm but the heater didn't heat well, turned out the lines had a bunch of gunk accumulated which was resolved by flushing the system -- I went so far as to remove a number of the hoses and clean them separately.

Brian, can you upload that Leno appearance on Youtube? I missed it the first time and would like to see it.

It's a 99 Nissan Frontier truck. 80K miles. I've never had the radiator flushed.

I bet this solves it. We had a cold air blowing heater (in a Nissan in fact) and it was the thermostat.

I once had Jetta that would vapor lock and the hot engine light and buzzer would come on. Drove it across the nation that way. It only vapor locked once, outside of Grand Junction. Eventually, a new fuel pump solved the vapor locking, but the hot engine light and buzzer continued to come on. Beating the dashboard was the only solution I found. I was born in Idaho.

Sounds like your thermostat is sticking to me. I'd start there.

is that generally easy to fix?
I'm trying to teach myself how to do basic repair.

i sure wish i would have taken auto mechanics in HS. it would have saved me more money in life than that karate class.

Yes it is generally easy to fix. Get a manual for your truck and then buy the part and replace it yourself. It is an afternoon job, if you don't know what you're doing, and it iwll save you money and give you more satisfaction than touching parts of your face with your tongue.

thermostat very easy
 

Generally speaking the thermostat repair job is one of the easiest. Generally it involves removing a hose clamp, prying off the hose. Unscrewing two bolts, removing the thermostat and reversing the process. The trouble is knowing exactly which hose, so its good to have a manual. First guess: the large diameter hose going directly from the engine to the top of the radiator.

You might as well flush your radiator at the same time because 1) you're going to lose some fluid in the process, 2) you really don't know the thermostat is the problem in this case, 3) you said its never been done in 8 years. The anti-freeze and the water pump lubricant in the water has a limited lifetime. I'd say its much less than 8 years.

Bad news: the coolant fluid is poisonous to pets (I've read cats like the taste) and is terrible for the environment, so any lost fluid should be captured and recycled (take it to any place that does oil changes and the like). So you're asking, "How do I catch all that water and transport it?". There's the rub, so you might want pay someone to do a professional cooling system flush. My guess about 80 bucks at an independent shop. If that's over your budget, I'd start by putting a large bucket under the radiator and remove the plug. That should catch the bulk of it. Then every time you remove a hose some may also spill out that didn't drain all the way through, try to catch that, too. Then liberally hose down your drive to dilute anything that you missed.

PS: My school didn't offer stuff like "auto mechanics", I learned from my dad and my friends. Its always good to know a gearhead.