2002 impala losing radiator fluid

Working on this 2002 Chevy Impala 3800 series 2 engine. I have checked the coolant overflow and heater core. Replaced cap, thermostat, and upper radiator hose.

Water pump isnt leaking or squeaking, no water appears to be coming out anywhere that i can see. Car uses a cup of fluid per day! My guess is that it's leaking into the manifold. I have done this job before. I just want some confirmation before I just take it apart. So should I go ahead and do the manifold gaskets or run some more tests?

fyi, it's not misfiring, not smoking, and doesn't have any pools of water under it when parked overnight.

Any help is always appreciated, thanks.

Sounds like you may have a intake plenum leaking.

Good, just wanted a second opinion. thanks m8

Working on this 2002 Chevy Impala 3800 series 2 engine. I have checked the coolant overflow and heater core. Replaced cap, thermostat, and upper radiator hose.

Water pump isnt leaking or squeaking, no water appears to be coming out anywhere that i can see. Car uses a cup of fluid per day! My guess is that it's leaking into the manifold. I have done this job before. I just want some confirmation before I just take it apart. So should I go ahead and do the manifold gaskets or run some more tests?

fyi, it's not misfiring, not smoking, and doesn't have any pools of water under it when parked overnight.

Any help is always appreciated, thanks.

what about pressure testing the coolant system first. then go from there. intake/head gaskets are possible.

remove spark plugs for coolant evidence .intake gaskets should reveal leaks easy/ head gaskets not so easy.

You may have a small leak from the 90 degree plastic elbows , which come out of the engine block going through the idler assembly then going to the heater and back to the block . Being plastic , they become brittle with age and the only method used for sealing are O-rings . They are right above the water pump and the leakage can be so minute that detecting it is very difficult ?

It loses enough fluid to overheat in 4 days of normal driving. It would be a large leak. I will try the pressure test and also check the plastic pipes.

I did already look in the UIM and saw some goo crap that wasn't oil. Good idea to do the manifold gaskets anyways. Junk plastic ones go out eventually and this engine has 200k on it.

Thanks for the replies :)

It loses enough fluid to overheat in 4 days of normal driving. It would be a large leak. I will try the pressure test and also check the plastic pipes.

I did already look in the UIM and saw some goo crap that wasn't oil. Good idea to do the manifold gaskets anyways. Junk plastic ones go out eventually and this engine has 200k on it.

Thanks for the replies :)

with the coolant cap off engine running see if the coolant bubbles out . pressure test should reveal the leak with what you just stated.

Thanks for all the help. It was the plastic heater pipe! Couldn't see it till I took the manifold off. When I removed the lower manifold the pipe just disintegrated, I finally got it all out in about 5 pieces.

The upper manifold gasket needed to be changed anyways, also found a bunch of oil in the intake so the job wasn't a waste. :icon16: