Help me find the source of the coolant creek flowing out the bottom of my STR!

Last week as the header tank coolant leak thread developed, I sprung a coolant leak in my 04 STR. A nice steady slow drip-drip-drip!

I did all the normal visual tests trying to spot the leak. Nothing! All I can see are drops of coolant dripping off the front of the oil pan at the front of the engine.

Next I took aff all the plastic parts around the engine including the plastic inlet manifold so I could get a better look at the water pump and pile of hoses on the front top of the engine. Now signs of coolant visible.

Then I pressurized the water system by removing the threaded bleed plug in the top of the header tank and installed a threaded hose disconnect. I pressurized the coolant system, and the coolant started dripping again. I looked up close with a light and mirror, all around the area above and around the water pump. There is so much crap in the area that there is not very good visibility.

Thus I am looking for input for the most likely source for the leak.

- I've eliminated out the following.
1. Thermostat housing to manifold.
2. Aluminum manifold where it bolts to each head.
3. All the inlet and outlet hoses to the Super's inter-coolers.
4. The smaller hoses that route back the the header tank.
5. The header tank is not leaking at any fittings.
6. The large main inlet and outlet water hoses.
7. It is not in the lower left area of the engine were the little valves are.

I do not have good visibility to the bottom of the water pump, nor can I see much of the large short hose that comes off the thermostat manifold and goes below the supercharger drive housing into the front middle of the block.

Help!

 

We read so much here about the STR's "dreaded under-the-supercharger coolant hose failure". I don't have an STR, but I suspect that is indeed your failure point....

 

The under SC hose usually leaves a red stain down the back of the engine. So I don't think that's it but can you check that area?

Here is a good diagram. Like I posted I had two pin hole leaks and they were hard to find even when the engine is cold!!

4.2L SC


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Thanks for the Diagram. It provides better visuals.

I didn't work on the car all week and this morning while it was still cool weather, I decided to try to find the leak again.
I pressurize the coolant system. Sure enough, within a few minutes, the same drip-drip-drip appears out the front bottom of the engine. I carefully traced the leak as far as I could see up the front of the engine. Definitely coming down the front center of the engine block. Right where all the hoses, and water pump are.

I removed all the upper hoses and inspected them all. One of the small tank return hoses looked split, so I cut off the end and shortened the hose just to be sure. After I put all the hoses back on, I pressurized the system again. Still leaking.

Based on the diagram, all that is left that could be leaking are items 7 and 9, or the water pump.

The weep hole for the water pump is located on the top of the pump, so I think I would see coolant coming out of that area, or coolant being sprayed off the pulley. I don't think it is the water pump.

After this failed attempt, I pressure washed the front of the engine area, (not really that dirty) and after it drys, will try to find the source one more time.
If I can't find the leak, I will have to take everything apart.

 

Did you ever figure this out?

 

No. I've been working out of town. I hope to take another look this weekend.
I figure I will have to put in a flourescence dye and try trace it to the leak.

 

How many miles on the motor? Maybe the waterpumping is weeping?

 

When we were searching for my leak it ended up being the radiator itself with a very small leak. Here is the pic from the radiator bracket.

 

I purchased a new water pump originally thinking that was where the leak was coming from. As far as I can tell, the pump is't leaking.

Hopefully I'll be able to work on finding the leak this weekend.

 

The other day, I purchased some UV light additive and put it in the coolant reservoir. Drove the car for a while to circulate the additive.

Today between rain storms, I took a look a what had leaked out.
I've found 2 leaks. The first, was at the coolant reservoir bypass line (#3 in earlier attached image) at the manifold. fluid was leaking around the stock hose clamp. Replaced the clamp and that leak went away.

The main and second leak is coming out of the water pump area. Either the weep hole, shaft seal or gasket. Looks like I need to replace the pump!

Any special hints on and STR?

 

I found the leak! Yeah!

It looks like the previous owner/mechanic who last worked on the car, damaged the sealing portion of the pump. (See image.)

I will be putting in a new pump today.

Finding this leak was not fun. After I decided to remove the pump and removed the fan belt pulley, I could finally see where the coolant was leaking out of the bottom between the pump and block.

 

Congrats on nailing it down. Let us know if a new pump indeed solves your issue....

You aren't running traditional green-colored coolant, are you? I assume that's the UV dye you added....

 

So far so good. No visible leaks.
The UV dye turned the coolant a very bright green. The coolant I use is orange stuff.

Thanks for the tip.

Joe

 

Tijoe, Do you remember the thread size/ type in the header tank? I need to pressure my system to find a slow leak which is not readily apparent. The thread on the bleed screw does not look very standard at all.
Thanks

 

Have you checked the nipple directly below the cap?
When mine goes bad it weeps ever so slightly, a lot less than my wallet, there because a crack develops and you see remnants of coolant on tanks seam/lip just below the nipple.

 

I used a standard pneumatic male x male quick disconnect fitting wrapped with Teflon tape.
I was careful to tighten it by hand so I wouldn't strip the plastic threads in the header tank. (Threads are different pitch, the fitting being NPT). It leaked a little air, but my compressor supplies way more than leaks. Be careful not to put in too much pressure.

 

Thanks All, I was able to get a steady drip without applying any external pressure. It looks like the DCCV which is located directly below part #5 in the diagram earlier in this thread. And yes indeed I had to replace the header tank last year with a cracked nipple.