When Should I Replace Heater Core "O" Rings?
 

Have a 99 Range Rover 4.0 SE with about 98,000 Miles on it. Dealer is recommending I replace the heater core "O" rings. Minimal cost in parts, major cost in labor (time it takes to get at it). I have no signs of leakage that I can tell, heater works fine. Is this a good preventative measure and should it be done at this mileage, or is the dealer just fishing for extra work at my expense?

I'm all about preventative maintenance however this is one of those things that "if it ain't broke, don't fix it." I would replace if I was ever in that far and I would continue to check for symptoms but I wouldn't fix it just for the sake of doing it.

I agree with Krazzz, wait until it leaks and then maybe replace it. If it is being used then it can defianyely go longer before it needs replacement. My heater has 160K on it and it is still performing just fine.

here's what you can do to figure out if it needs to be replaced.
1) keep an eye on your coolant level, check it daily weekly cold by looking at reservoir tank. if it's dropping, you have a leak.

2) check in passenger side footwell for moist carpet, the hill side closest to radio by passenger left foot. just above this is the O-ring. smell your wet fingers...(insert joke here) it's probably antifreeze. time to repair.

Repair Choices:

1) replace the O-rings yourself for $8 and a half-day's worth of work
2)pay a dealer a ton of time, when they can actually do it in like 3 hours with the new shortcut
3)$10 Bar's Leak. This stuff is awesome, but there's a process. the only place to add coolant is through the reservoir but it has to get into the radiator and circulate. here's how to accelerate that process:

-Add the bar's leak (Pep Boys) to reservoir
-Drain radiator by about 1 gallon into a container by accessing the plug under the bumper (it's black, and a screwdriver will work or a 3/4 ratchet). this pulls bar's into system.
-add gallon of coolant back to reservoir
-turn heat on high for 5 minutes
dry your carpet, and check in a few days. if it doesnt stop it, change them. should totally work. this stuff is great.