Can you guys help me track down this leak? A bit of info about my car first: 2004, 80K miles, reman about 20K ago, Mazmart water pump and thermostat installed about 3 months ago.

I have a very slow leak that I only noticed from the smell coming into the cabin when my car was warmed up and at a stop and a bit of a smell in my garage after parking the car. After searching high and low for any coolant (there is none on the ground or under the car) I finally found a small puddle on top of the engine under the intake manifold. Below is a picture of where you can see the coolant puddled (there are actually two puddles there, but the larger one was impossible to get a light on and get the camera to capture it at the same time). Using Prestone coolant, which is orange. I've found no coolant on or around any hoses or connectors that I can see. Does anyone know where this leak could be coming from?

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I think you'll need to tear it back apart and look for this yourself.
You didn't take the whole thermostat housing off... right?
You only removed the upper part of the housing?
Also in that area is where the ECT (engine coolant temp) sensor is located.
But like I said, its a guessing game until you get back down there and look.
Removing the UIM might also help you see more from the back-end.

 

...or maybe get an illuminated inpection scope to diagnose without heavy disassembly. Home Depot has a Ryobi Tek4 unit for under $150. Depends on what you value your labor hours at...

 

I have a silly idea. Does your orange coolant glow under UV light? Might help locate the leak in darkness using black light.

 

I had a shop do the thermostat/water pump install, so I'm not sure what they did. But, I don't see coolant anywhere around the thermostat housing, so I don't think that is it. Also, I think if there was a leak from the thermostat, it would make it's way onto the ground. Where exactly is the ECT sensor located?

 

Below is a pic lifted from RotaryResurrection's engine tear down thread. The yellow circles are where the coolant is. Can you point out the location of the ECT sensor on this pic?

 

AHH... the pic made it appear that the coolant was on the "ledge" under the ECT.
Didn't realize it was that far back.

 

The ECT sensor is the grey plug just to the right of your circles

The only thing that goes through there with coolant in it is the throttle body coolant hose.....

If it is leaking from anything else there..... it is coming out between the housing and irons...and you will need a new motor to fix it

 

If it was coming from between the housing and iron, would I notice anything else? The car is running great, haven't noticed any performance issues.

 

Nope...there is an inner seal...and an outer seal...if it is leaking between the outer seal and the outside it will just leak

 

That's terrific! I suppose I'll have to take it to the dealership.

 

I would clean it out really carefully and then see where it is coming from. Check the hose first

The dealer will likely add UV dye to the coolant to see where it is coming from

Has it ever overheated?

 

I cleaned it out best I could today, but I have to drive it to get it to leak so it's hard to tell where it's coming from.

Yes, it has overheated, that was the reason for the thermostat and water pump replacement.

 

I wouldn't tell the dealer that unless they already know Overheating is likely going to void your warranty

 

Failure of the OEM thermostat will void the engine warranty?

 

Failure of a non-warranty part could void the warranty..best to leave out the potential

 

dealership "ignorance is bliss" in this case may work out.

 

Yeah, dealership knows nothing. I'll lose my mazmart waterpump if I dont say anything. :-(

 

Want a stock one...I have 3 spares...

 

I've still got my stock one too... I just don't want to go through all the work of installing it. Ugh!

 

So I cleaned the area and drove to work and back and around doing some errands at lunch and I wasn't getting the coolant smell coming through the vents when stopped at lights. Got home from work, popped the hood and there is no new coolant in that area. WTF? Did my car self heal? Anyway, I'll keep an eye on it and keep this thread updated.

 

Might have sweated a bit with the overheat......

 

Coolant leak is back. I'm going to take it in next week.

 

Well, this turned out to be the worst case senario and a reman was needed. The good news is that I tried a new dealership and they seem to have done an excellent job with the install (my first reman was such a huge headache because the dealership made so many mistakes, many of which ended up coming out of my pocket to fix). All was covered under warranty, although I lost my Mazmart water pump (I asked if they'd swap it, and they were fine with the fact that I had an aftermarket pump, but they had already taken pics of then engine and sent them to Mazda and didn't want to risk a fine). I'll pick up another next time I decide to do a coolant flush. Thanks dannobre and anyone else who chimed in with advice!