I was under my '97 4Runner today cleaning the rust with a wire brush before putting rust bullet on it when I noticed a small leak! The leak is coming from underneath the passenger side, near the tire, there are two cables/pipes there, running closely together. The fluid that is dripping out drip by drip is yellow, but I do not know what fluid it is because I don't know what pipe it's coming from. Is it gas/oil/front axel oil?

How do I fix the leak? I put a papertowel around it and wrapped it with some electrical tape as a temporary fix while I figure out how to fix it.

Can I buy some kind of product that will seal the hole? Maybe something that could be spread all over the pipe so I don't get any more holes?

Do you have Rear Heat??

If so, it might be the rear heater lines are rotted and sprung a leak.

There are a few threads on here about rotted lines.

If it was gas, you probably would know by the smell.

I will do a search on here for rotted lines, I never use the rear heater, should I even try to fix this line or just let it drip out? Would I still have heat in the front if I let this leak all the way out?

Sounds like rear heat lines to me. They are very easy to remove. I took my rusty rear heater lines out last week. Here is a post on another forum. It's not my writeup but should help explain your situation.

HELP! Line running on the underbody busted and is now leaking pink - YotaTech Forums

You have to either fix it or by pass the rear heater. Since you don't use it, I would just by pass it.

Those lines are all part of the cooling system. It will just continue to drip until you have no more coolant left and over heat the thing.

check this thread out!! Do the lines look like this?
Help ID rotten lines and fluid

ALL of your coolant will leak out. Remove the rear heater lines. You can "cap off" the delivery and return lines at the firewall behind the throttle body. Follow the hard lines into the engine bay and you will see the rubber hose that you can use to circumvent the rear heater.

The lines are just delivery and return lines so they can "connected" via a short rubber hose at the firewall behind the TB.

Good thing you saw the leak before you lost too much coolant.

These are the lines I am talking about. Are these the rear heater lines?

You can see where I put the paper towel with electrical tape.

Any have any information on how to bypass the lines? I clicked on the YT links but have a hard time understanding what I am supposed to do.

Here is the quote:
The run to and from the rear heat is in the engine compartment back on the firewall. Disconnect one rubber line from the metal line going to the rear heat and remomve the other line from the outlet to the rear heat. Then connect the lines to the rear htr together with the hose. Then bypass the rear heat by connecting the other hose at the rear heat 'valve' (where the cable is). This bypass only took 1 minute but could have saved me 5 hours of numbing pain and frustration as I tried to fix it in the driveway.

However I have no idea how to do this, can anyone explain it better or perhaps post a pic?

If all of the coolant leaks out do I have to replace it or no?

Ok I think I got it figured out, I unhooked one hose from each section and then make two loops. I looked underneath the truck and looks like a lot more fluid came out, more than just a few drops. I think all of it came out while I was working on the hoses. This fluid is for both the front and rear heat right? How do I refill it and what kind of fluid does it take?

Heres a thread with a few pictures that might help.

Rear Heater Lines

Yes the fluid is for the main "front" and rear heat.

Fill it by the radiator cap. Only take off cap when engine is cool.
Being yellow in color I would guess it is the "universal" coolant. You can pick that up at any auto parts store.
Fill radiator first then check the overflow tank and fill until between the MIN-MAX line. Then drive check the overflow after a few days of driving. You might have to add a little to the tank.

Your screen name has 311, Are you a fan of the group??

Would you happen to have any photos showing exactly the two places where I should pour the coolant in?

Take a look at this picture. See if it helps you out.

Attached Images

 

I bought one gallon of Peak long life 50/50 prediluted antifreeze and coolant. Do I have to drain the old coolant or can I just add this one to it and top it off?

Open the cap, and check the condition of the coolant that remains. If its pretty clean, fill up the radiator, run the engine with the cap off, and allow the thermostat to open. This will allow any air in the system to bubble out. Just make sure to watch the radiator level, and keep topping it off. One it stops bubbling, and is just circulating, put the cap back on, and fill the tank to half full. Check in a few days.

However, if the coolant is dirty/muddy, it would benefit from a radiator drain and fill. Just open the petcock on the bottom of the radiator, take off the cap, and let it drain. Fill it back up, and do the same procedure above to "burp" the system of air. I would suggest getting a bottle of concentrate coolant (you have to mix this), and a gallon of distilled water >$1. This is alot cheaper for 2 gallons. Make the concentration 70% coolant to 30% water. This will add more cooling capacity to the whole system (like 55% coolant, 45% water), and that will cool the engine more efficiently.

Good luck

This Gentleman could not say it any better!!