Coolant Leak Diagnosis

[The Critic]

2006 Accord V6 with 137K miles.

This car came in for rear brakes. While driving the vehicle into the shop, I smelled coolant. After opening the hood I found coolant on top of the radiator and coolant residue on the front engine mount reinforcemenr bracket. I removed the radiator cap to perform a pressure test, and found this:



After proceeding with the pressure test, I found the system to hold 14psi for hours. No visible leaks were observed. I tried pressurizing the system at a slightly higher pressure but it would bleed back down after 10-15 min. Strange.

With approval, I installed a new OE radiator cap. The area was cleaned and then the car was road tested for 5 miles. When I returned, there were still no leaks. I allowed the car to idle for another 15 minutes. Still dry. I kept it idling and came back after another 30 minutes (total of 45 min idling).

Bingo.



A tiny drop of coolant finally appears.

One tech claims that if the radiator cap breaks and the coolant level drops, the steam will etch the plastic and cause damage. Dunno. But I think the leak finally appeared after a new cap was installed because the new cap pressurized the system more, and any crust/gunk that was sealing the leak was dislodged.

Lesson is - investigate cooling system leaks thoroughly. It may take a while for them to show up.

 

[tomcat27]

Wow. That would have been way too easy to miss. Good persistance!

 

[Kira]

This is what I have to do on my car. After 20K of ownership the coolant reservoir level (dead cold) has simply crept down 40 mm (1.5").

Frankly, my car runs real well so a teeny bit of vanishing coolant is something anyone could live with.
However, this is my third V70 with the same engine and trim level and the other two never lost one coolant molecule.

I have looked around a few times and hoped to find the familiar "frosting" of coolant residue somewhere. No luck.

Does anybody know: Do all coolants produce the "frosty residue"?

ps To critic: You have a good sniffer to pick up a leak that small. I bet you don't smoke.

 

[E150GT]

All 3 of the Mazda I have owned lost coolant since new. I never smell it though unless I pop the hood after a long drive on a hot day. I just keep a bottle of FL22 on hand to top off every six months or so.

 

[The Critic]

I installed a new aftermarket Denso radiator ($64!) and vacuum-filled the system with GC Super Extended Life Blue Coolant. The driver declined new hoses and thermostat so the old ones were reused. I test drove the car and confirmed no leaks, and after the test drive, the coolant smell is also gone.

I also received approval to replace the rear brakes (Centric Premium rotors and dealer pads) and also brought all of the wallet flushes up-to-date (brake and p/s this time, ATF was done several months ago). Now the car should be ready for the road again.