: STS Radiator Hose Replacement

08-06-09, 12:53 AM
I have a '99 Cadillac STS with the NorthStar engine. Can anyone give me step-by-step instructions on how to replace the lower radiator hose?

I am only a backyard mechanic and not a very good. I could use the help.


08-06-09, 06:35 PM

Replacing the lower radiator hose is EASY. (Getting to it is somewhat more difficult.)

You will need a pair of pliers (channel locks would be best) to remove the hose clamps.

I'll write this with the assumption you have no experience whatsoever (not meant as an insult, just want to make sure you understand regardless of experience level)

1) Take off the plastic beauty cover covering the radiator
2) (you can skip this step, but it will be messier) The radiator drain plug is on the bottom, driver's side. Get a clean bucket or clean large, deep pan to catch the coolant, then unscrew the plug and let the coolant drain out. (Use a clean pan or bucket so you can reuse the coolant, if it's new enough. If the coolant has been there for more than 2 years, I would dispose of it and refill with new.)
3) The radiator hoses (upper is the one running across the radiator, under the beauty cover) are held in place by spring type clamps. Squeeze the clamp with the pliers and slide it toward the middle of the hose until it's clear of the fitting the hose is on.
4) The hose will probably be stuck and not want to slide out. Twist the hose back and forth with your hands (or the pliers - don't squeeze too hard!) until the end of the hose is turning left and right on the fitting. Now you'll be able to get the hose off the fitting.
5) Once the hose is off, slide the clamps off the old hose and onto the new one.
6) Slip the hose onto the fittings (radiator side first, it's easier that way) until seated.
7) With the pliers, slide the clamps into position (same position as on the old hose)
8) If you took it off, replace the radiator drain plug.
9) Top off coolant (either your old one, or new mix of half DexCool and half distilled water), then start the car and look for leaks.
10) Let the car reach operating temp, then turn it off and let it cool down all the way (preferably overnight). Once cold, top off coolant again to 1/2 a tank, at the cold fill mark. Don't overfill - if you do, the excess coolant will be sent out the overflow tube the next time you drive the car.
11) Check for leaks again, if none found then reinstall beauty cover.

You're done!

08-07-09, 12:31 AM
THANKS for the great help. I needed it. I would have gone in from the bottom !!!!!!!!!!!!!!

08-19-09, 05:51 PM
i dont even know if im posting this in the right place!!how do i get to the radiator drain plug on a 96 sts. i can see it i just cant get to it.im needing to do a radiator flush.any help would be much appreated.

08-19-09, 06:39 PM
I have the same question, also for a 96 STS, does the lower plastic guard (with 5 bolts holding it in) have to be removed to get to the plug, or is there an access hole that I'm missing?


Edit: found a discussion here, I'm just going to pull the lower hose: http://www.cadillacforums.com/forums/northstar-performance-technical-discussion/153383-where-radiator-drain-plug.html

08-19-09, 07:41 PM
I replaced the water pump belt, the motor mount (rubber was completely shot), and the upper radiator hose while I was in there. The lower looks difficult to get to and it was getting dark so it will have to be another time.

The rest was easy, once I removed the belt tensioner.

Any more tips for the lower hose would be appreciated.

08-19-09, 07:46 PM
Remove the plastic splash shield under the car and it should be much easier to get at.

08-19-09, 08:44 PM
............and make sure the upper radiator hose is gently tie-wrapped out of the way of the front of the engine or any pulleys.............

08-19-09, 10:48 PM
Thanks, will remove the plastic panel next time.

Yes, interesting that the old hose seemed slightly swelled, and the old belt streached making the loop around the tensioner just touch the old hose.
I will tie the new hose back away from that pulley.

Thanks to you both for the tips!

08-20-09, 07:44 AM
Pete, I believe the pre-2000's used one or two plastic band clamps to keep the upper hose close to the radiator brace. 2000+ have a channel, molded into the underside of the upper radiator plastic cover, into which the upper hose clips.

08-21-09, 01:11 AM
hay Pete, or anyone for that matterJason(jbeau302) with the 96 sts.i took off the top shield and the bottom one.i can see the drain plug (bottom or radiator driver side facing the motor) also what looks like a drain hole at the very bottom of the radiator.i just can get my hands or a tool to it( the plug).i got the prestone flush kit that you hook the hoes up to but i read on one of there posts not to usr regular h2o,ues distilled.any help would be great.step by step or even tips and tricks. feel free to pass this along to anyone you think may be able to help.

thank you

08-21-09, 11:40 AM
From your description I think you loosen the plug, but it does not get removed and thus drains out the bottom hole. Get yourself a 6" length of 3/4" dowel rod. Cut a 1/8" slot in the end. Slip that slot over the drain plug "wings" (for lack of a better word) and use it as a tool to loosen and tighten it.

11-13-10, 03:12 PM
Remove the plastic splash shield under the car and it should be much easier to get at.

OK, I'm finally doing this since the hose is leaking. Removed the lower shield - that helped
but I'm finding that removing the air box also helps get some room to work in there.