Coolant Leak

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Feb 27, 2005
My 2000 LC is slowing losing coolant from the coolant bottle.

This started after my 100000 mile service where I did the water pump and timing belt.

I took it to the dealer who pressure tested it and tried to tell me everything is fine. But it continues to lose fluid...It has been several months since the service....

Any ideas on how to troubleshoot this....?
I'd bring it back to the dealer.
what does that mean, "losing from the bottle"? you mean the level is going down or you mean the bottle and hardware is leaking...? (Hopefully the latter)
The level in bottle drains down about every couple tanks of gas..

Am heading back to the dealer but trying to narrow it down..
Are there any signs of dried coolant stains (white or red) on engine parts or the block?
My guess is that it would be somewhat normal depending on how much you are "losing". If the tech did not use a pressurized method to replace the coolant, there will most likely be some air in the system. The air will eventually get out and coolant will be sucked from the overflow bottle. The 60 series is terrible for trying to get all the air out of.

I'd take it back and tell them to get the air out of the system, or do it yourself.
do you refill into the top of the radiator or into the overflow tank? If the former, try the latter and see if it stabilizes.

FWIW, I haven't kept track of the 100 much, but on my 80, the level in the overflow tank has not visibly lowered itself in several *months*! So, I would say if the tank empties itself every couple of gas tanks, that there is a serious leak someplace. If you can't find it easily, you can put some ultraviolet dye in there and find it that way, if it's external.
It is possible that system "burping" after drain & refill will cause the bottle level to drop over several successive thermal cycles (cold system - hot system - cooldown - repeat), as the air burped out of a hot system is replaced by coolant drawn back in from the bottle at cooldowns.

But this should not continue for several months.

You could have a very slow leak at one or more of several places, not giving external visual signs: Water pump, head gasket, other places on or in the engine assy.

If coolant leaks very slowly at the water pump, for example, it will evaporate on a hot engine and you will not see any coolant per se unless you can get a small mirror in to see the relief hole when it is leaking, or a finger in to feel wet coolant. But you will smell it under certain hot engine conditions, if you have a good nose and believe what it tells you when you open the hood to check.

Since your issue started after the water pump was replaced and has continued long after any burping should have finished, that gives you a clue.

The pressure test can find these sorts of very slow leaks, but like lots of other diagnostics, its only as good as the Technician who applies it and the quality & condition of the tool itself. Maybe your pressure testing found no leak because there is no significant leak - or, maybe it found no leak because it was not done correctly or the tool is in poor condition.
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Big Bert said:
My 2000 LC is slowing losing coolant. This started after my 100,000 mile service where I did the water pump and timing belt.

I think it is more than coincidence that the leak started after this service work. Check the drain cock on the radiator and the two on the engine block. Check the radiator hose connections and the small coolant hoses at the oil filter oil cooler. Remove the right side timing belt cover and look at the water pump. Slow leaks sometimes heal themselves and that's probably what the service deparmtent is hoping for.
I had a mysterious leak in my 4runner after flushing w/ new coolant last spring. It would also take about 2 weeks to drop to the low point in the bottle, yet I never saw it leaking. System was burped, as I flush on a slope and run the engine w/ radiator cap off. This went on for several months. Gradually, I'd notice more and more splatter stains of coolant all over the steering components/alternator, but no drips down the side of the block. I'd drive 17 mi to work, pop the hood, yet no leaks anywhere. Turns out it was a hose that would weep only when the engine was warming up, but not warm. The fan would then blow it all over the place. The reason is, when the engine is cold, the radiator cap has a valve that's closed. Thus, as you start to drive and the engine warms up, the system pressurizes. That's when the leak occurs. After it's warmed up, the radiator cap valve opens, and the expanded coolant flows into the overflow tank. I finally found the leak after driving a couple of miles to gas up. I'd either try something like that or have it pressure tested. That should also detect the leak. The culprit leaky joint was right next to the exhaust manifold/header, so the extra heat combined probably did the hose in (original hose was replaced at 130K as PM, car driven in CA/WA; replacement OEM hose lasted only 60K mi, driven in AZ). Let us know what you find out.

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