So I just ran a few errands in my 99 and got home, turned off the ignition, and was walking in and noticed a 'hissing' or 'spewing' noise. I followed the sound and it seemed to be coming from underneath the firewall area near the transfer case or transmission. It was easily viewable from the passenger side that there was steam coming out as well.

It snowed 17" here and driving has been rough, using high 4 all day some low 4 for a bit. Never noticed it any other time during the day.

Is it possible its just water/ice on something hot? I feel like it wouldve been doing it throughout the day if it was that.

The noise started to slowly die down too after a minute or 2. Makes me think, pressure from a hose or something?

No noticeable smell at all...too dark to pinpoint where it was coming from

My guess is it would have to be something in the cooling system, maybe a pinhole leak in a hose? Check your coolant level and reservoir.

could it be snow on the exhaust melting?

^^ what I was thinking

Thats what i was curious too ^ but it was pretty loud and it hadnt done it at any other time today

If you have the rear heater it may be the steel lines that run under the passenger side of the vehicle. They are notorious for rusting out and leaking!!!

Sure enough...about a block from my house this morning the temperature guage sky rockets.

Whats your tranny fluid look like

So i took it into local shop...it was the heater lines that rusted out!

Question..they quoted me $570?! Is that accurate? How much should i be paying for this? That sounds a little steep for 2 lines replaced and some antifreeze. It must be labor intensive?

Do it yourself:
Anybody interested in a rear coolant line repair write-up??

Most people just replace it with soft line.

In the meantime you can loop the rear heater feed back on itself. 5 minutes and a foot of hose. You will still stay warm.