My 2002 S-Type 3ltr has a coolant leak where the level drops to low in the expansion tank but no further. The coolant low light is on but the temp gauge reads normal.
The heater is also blowing out cold air only.
Are these related and what action would you suggest to fix.
Thanks.

 

Yes, the two are related. Heater performance drops way off, especially at idle, when the coolant level is low. The V6 is worse than the V8, too.

I take it you have refilled the coolant but it continues to drop off?

To find the leak, I'd recommend using a cooling system pressure tester. That way you can pressurize the system without the engine running or the radiator fan blowing any leaks around.

I've found with the engine running and coolant warm, small leaks often evaporate quickly, making them difficult to identify. I've had good results with a pressure tester on a cold engine.

If you do find an external leak, be careful with the diagnosis. The fan tends to blow any coolant around and it may collect in other spots and steer you wrong. That's why I like the pressure tester, so you're not dealing with potentially misleading results from coolant being blown around by the fan.

 

Thanks for the reply.
I'm pretty sure that the leak is in he expansion tank as the coolant level never drops below the bottom of the tank.
I suppose my question is will fixing / replacing the tank also sort out the problem with the heating not working?
Thanks, Graham

 

That's kinda like flying a helicopter and drooping your turns so low that the generators fall off-line and the hydraulics stop working. Then someone says, "Hey, if you don't get your turns (Nr) up, the rotor's gonna destroy itself and then it's gonna fly like a toolbox" and your response is, "Yeah, but if I get the turns up, will my generators come back?"

Coolant leak is a far bigger problem than lack of heat, and mending the former, as Karl proposed, will likely mend the latter. If not, you still need to mend the former first.

 

Um, not to be picky, but aren't anecdotes typically offered to clarify the issue at hand?

I work in commercial aviation, albeit the side that obeys the laws of physics (fixed wing), and have absolutely no idea what you're talking about. Did JoycesJag share some of his pain meds with you? Or are you saying the lack of heat is caused by a generator problem?

All seriousness aside, back to the coolant loss and lack of heat. Yes, they are almost certainly related. Just a hunch, but I think the loss of heat is caused by low system pressure due to the leak. Coolant doesn't flow as readily through the heater core, and I think it's because the flow pattern throughout the entire system is disturbed. That's just a guess, so don't take it as gospel. But my '02 V6 has had several instance of minor coolant leaks, and the lack of heat was my first symptom.

Don't just throw a reservoir at the problem, unless you find evidence of a leak there. Inspect the cooling system carefully for the leak. In my experience, minor leaks are hard to find on a warm engine, but they showed up readily using a pressure tester when cold. Many parts stores offer free loaner tools if hesitant to purchase one.

 

​​​​​​Hey now, I understood Zane's anecdote perfectly!

 

The two issues may or may not be related. The coolant leak is certainly the more worrisome and should be corrected as soon as possible with the installation of a new expansion tank.

The lack of heat could also be caused by a malfunctioning DCCV, which is also either leaking or stuck in one position.