Going to attempt to find a coolant leak on my 03 STR this weekend
 

So about 6 months ago I changed the belts and the water pump because I had a slow leak and it seemed to be coming from that area. Low and behold, the water pump had a cracked impeller, so I'm glad I did it. However, the leak is still there (a relatively slow leak). There are some puddles in the area above the water pump and under the supercharger snout (where all the hoses are).

My plan was to run some UV dye in the car for about 15 minutes, and then try to find the leak. Unfortunately I don't think I can see much without removing the coolant expansion tank and probably the water pump pulley.

Anybody have any suggestions for finding this leak? I even tried using a pressure tester, but it's hard to see anything without removing hoses or coolant tanks.

Thanks.

I know the feeling...that tank is right in the way....i used my pressure tester and took off the underbelly pan and the one under the radiator..,..then while the car was on jack stands i got underneath and started looking for the coolant trail....i had a helper to keep the pressure up and also move hoses around up top...i finally found the trail and it led me to an intercooler hose tee fitting....the hose had worn at the crimp....i cut off the crimps securing that section of hose and replaced that piece of hose and secured with smooth band norma worm clamps....a helper really makes the job easier

Go to your auto parts store and get some dye. That shows up leaks pretty fast. Follow the instructions.

So for an update, I had an Indy look at this, and after having the pressure tester on the car for a couple hours, they didn't see any pressure drop and couldn't see any leaks. I know there is an external leak, but it must not leak when the car is cold. Maybe the coolant has to be running and hot before it actually leaks? I have to fill the coolant from the 'min' mark about every couple of weeks, so it's definitely leaking, and I can smell the burning fluid as well. My next thought is to rent a pressure tester and leave it on overnight just to see if I see any pressure drop.

I'm just wondering if anyone has ever heard of coolant only leaking when it's hot and running.

I tried the dye before I took it to the mechanic, but for some reason, I couldn't see it even with the special glasses and blacklight. The kit I bought on Amazon was probably crap.

it could very well be a leak that takes both heat and pressure to show up. More than likely it is water vapor which is very very hard to see. The most likely culprit is the plastic pressure tank or cap I went through three oem pressure caps before I finally decided to get one made by stant and that cured my problem

I'm just starting the under supercharger hose replacement.
I tried the same thing as you and I couldn't see a GD thing from above even with a borescope snaked down in there and the proper trace dye (GM style for DEX-Cool which is what I'm using). I never saw a thing.

I drove the car on vacation and that's when it started leaking. Sometimes it would lose a half gallon quickly. Other times it went 70 miles and didn't drop at all. Weird. But finally it just began stream down the back of the engine once I had it up on jack stands. If you're going to try and drive carry lots of distilled water, no use wasting expensive coolant. Be prepared to hurry home and then deal with it. My system held none to very little pressure so I knew it was broken. Maybe yours just isn't quite there yet? Or it's something else completely but given it's an STR ...

Fun stuff no?

How did you figure out it was your cap?

I have an older snap on pressure tester that could do the radiator but not the screw cap.....I never felt the oem caps were tight enough....just a hunch and experience there...I finally bought the cap adapter when I bought the stant cap....all 3 oem failed.....the stant passed and when I tightened it, I could feel the gasket contact and tighten more before clicking ....I have read threads about pinhole leaks and even plastic degradation leaks from the tanks where you smell and lose coolant, but there is no visual....always under pressure and at operating temp.....if you do tank replacement, most members will recommend mayle or oem I believe....I have not replaced mine so no help there

Pressure testing the cooling system is best done after a cold-soak, such as overnight. Be sure to use the correct adapter and get the pressure to 1 bar. If the tester indicates less than 1 bar after ten or fifteen minutes, there is a leak. The two most common areas for leaks are the expansion tank failing and the coolant return hose under the supercharger.

Thanks for all of the tips. I'll rent a pressure tester again and try it in the morning. I'm also going to get under the car and look for the dreaded red stain near the back of the motor.

You'll have to drop the belly pan. Put it on a lift or on jack stands Read up about where to place the jacks stands in the front.

I got under the car this morning. I didn't see much on the passenger side, but I did see something on the driver side near the back of the engine where it meets the gearbox. I have added two photos here. It looks like coolant on a couple of the bolts, but I also see a stain running down (on the transmission I believe) which you can see circled in the first photo. Is the driver side where you would normally see the stain for the infamous hose under the supercharger issue?

https://cimg0.ibsrv.net/gimg/www.jag...2b18ca5bd3.jpg
https://cimg1.ibsrv.net/gimg/www.jag...993a1e5e4b.jpg

Coolant in that location usually means a leak from the hoses underneath the supercharger.

My supercharger hose leak was on the right side of the motor. From the hose that runs under the blower from thermostat housing to the EGR. But theres a similar hose that goes from a center engine inlet to the TB thats on the left (drivers) side