Heat for 10 secs, already reverse-flushed....

[mnikki99]

My 99 Jimmy only blows warm air for the first 10 secs that the heater is turned on, then it goes to cold air. If I drive for awhile at any speed and turn the heat back on again, same thing - it's warm for the first 10 secs then cold again. I've had the heater core reverse-flushed, last year I got all the way through the winter, this time it lasted two weeks. Could it be a vacuum problem? Or should I get the radiator flushed? My step-dad (who reverse-flushed it) suggested a new radiator cap.

Also, if the heat is set for the dash vents and I try to turn it to defrost (or anything else), it doesn't switch from the dash vents right away, sometimes it takes several tries of switching between all the other vents to get it off of the dash vents.

Any suggestions would be appreciated, I'm on the edge of a long, cold Minnesota winter! If I can't fix it, I guess I'll have to get one of those personal car heaters and try to trade it in next summer (the A/C does work!)

Thanks for your time...

[mnikki99]

Radiator flush and new radiator cap, heat works really good so far...

Now it's making a rattle noise when it starts up, the noise stops after driving a couple of blocks. Guages appear normal. <<<sigh>>>

[BlazerLT]

I don't think the rattle is related.

[mnikki99]

I found out yesterday that the rattle might be due to bad fan bearings, I can move the fan back and forth so I think it's hitting something. Not completely sure yet though.

Heat still works, I'm crossing my fingers...

Thanks for the reply!

[bearcatdon]

I ran into a weird noise when I started my 94 then it would disappear. It turned out to be the fan barely hitting the shroud. I trimmed the shroud area and it was gone.

[BlazerLT]

Wake up!

It hitting the shroud does not mean you trim the shroud, it means you fix the fan bearing or the water pump.

[bearcatdon]

I hear what your saying but when I say trim I mean trim and not cut out. I removed about 1/8 inch of thickness to 1" area. This was done with the thought that the shroud had warped. That was 2 years ago and I haven't touched it since. If it was truly a bearing, it surely would have gotten worse by now.

[BlazerLT]

Just be mindful.

The only times I have seen a fan touch a shroud it has not been the shrouds fault.