I have a Coolant Leak but I cant pinpoint where it could be leaking from. I did a coolant pressure test and notice the pressure was dropping. From there I could see coolant leaking from under my car. I looked under my car and could see it was coming from my the engine block but couldn't pinpoint the leak from the top or bottom of the engine.

Question:
I have an annoying check engine light code P0420. I have been reading around and they say it could be a bad head gasket leaking coolant but wouldnt that be internal leak and I wouldnt be able to see it leaking. I came to the conclusion that it might be a leak at the intake manifold. Which I hope it is.
Can an intake manifold coolant leak cause a code 0420. If it is how? How can I test if the intake manifold is leaking?

Car:
97 Chevy Tahoe 5.7L 4WD

Any help would be appreciated.

 

PO420 is a catalyst error. Could be an O2 sensor.

I would pinpoint the leak before I started taking it apart. It might even be a freeze plug. Would a mirror help?

A leak into the exhaust could contaminate the O2 sensor. A head or intake gasket failure could cause the leak.

Other ideas:
http://forum.doityourself.com/automo...ot-answer.html

 

99.9% of the time PO420 is a bad converter. Your leak is not causing your check engine light at all. It is most likely your intake.Where is it leaking front or back. If in the front, move your alternator and Ac compressor then re pressure test it.

 

another way to test that manifold is to buy a can of carb cleaner and spray around the areas where the manifold bolts up and see if the idle changes not only that but it cleans the whole area that way you can eyeball the leak! hope it helps keep me posted

 

My 2000 Hoe with the 5.7 had a coolant leak...up front near the thermostat housing. It was the lower intake gasket.