cooling fluid consumption (1 Viewer)

[64fabius]

On my 1999 LC UZJ 100, during this summer time, I've replenished about 400 ml (13,5 oz) of coolant every 1600 mi, but I've not observed any leaks. Is it normal?
On last full service, I flushed the radiator and filled it with new cooling fluid. Also thermostat and hoses were changed and I carefully bled the whole system.
What is your experience regarding it?

 

[Nightbrew]

How long ago was the last service you speak of?

 

[TheForger]

but I've not observed any leaks. Is it normal?

Trust me - there’s a leak if the level is decreasing. No that is not normal. The question is whether the leak is internal (ie. Head gasket leak causing oil & coolant to mix) or external (a fitting or clamp). The external leak could be dripping somewhere that’s not obvious like on the inside of your skid plate. Crawl underneath with a flash light to inspect and change your oil to see how it looks.

 

[64fabius]

Trust me - there’s a leak if the level is decreasing. No that is not normal. The question is whether the leak is internal (ie. Head gasket leak causing oil & coolant to mix) or external (a fitting or clamp). The external leak could be dripping somewhere that’s not obvious like on the inside of your skid plate. Crawl underneath with a flash light to inspect and change your oil to see how it looks.

I removed skid plate and I inspected underbody with a flash light: no external leaks.
I checked under the cap of motor oil but there are no signs of emulsified oil. No sign of white smoke from exhaust pipe.
The temperature of engine has been always normal and I've never observed overtemperature.

 

[MJK]

What is the level in the overflow bottle, and if you know, has it changed?

 

[64fabius]

What is the level in the overflow bottle, and if you know, has it changed?

The level in the overflow bottle is always the same from few months ago.

 

[MJK]

How full is the overflow bottle - nearly completely full or not?

The hypothesis I am trying to prove or disprove: coolant expands when it is hot, and the overflow is designed to capture the radiator spillover. If the overflow bottle gets full, it has a tube to dump it onto the ground. All of this, if it is happening, would most likely occur when the car is coming up to temperature with a radiator that begins completely full. When it cools, the radiator should draw back from the overflow. If there were a crack or leak in that hose that connects them, it won't do that. It would be like trying to drink slowly through a straw with a small hole - nothing but air. So, maybe you are losing the coolant on the first drive after the refill.

I don't know if that is the case, but if it is I suspect it would A) match your symptoms pretty closely and B) be most obvious after the first drive after a refill and C) result in a nearly full overflow bottle.

It is not a silver bullet, but it is pretty easy to check. Brim the radiator, nearly empty the overflow and go for a drive. If it cools and your missing radiator fluid shows up in the overflow then you have at least part of your answer.

 

[64fabius]

I checked the overflow bottle and all the hoses: no leaks. The level of coolant into the bottle is the same when I checked it few months ago.
Could leak derive from gaskets of water bypasses under the manifold assy intake?

 

[baltistyle]

Check the Hard coolant Tubes under the throttle body. I had a leak that then would burn off the evidence. The leak flowed to the valley. The thermostats housing also had a crack. Took forever to figure out. There’s two of these tubes. One is easy and one is not as easy. All aluminum so be carfule.

 

[Nightbrew]

I checked the overflow bottle and all the hoses: no leaks. The level of coolant into the bottle is the same when I checked it few months ago.
Could leak derive from gaskets of water bypasses under the manifold assy intake?

It can. I believe the connections under the intake manifold are sealed via o rings. However I feel like I have seen some pics or read, that there are some holes in the very back of the valley to allow liquid to drain out, presumably on top of the bell housing. Have you had the starter repaired or replaced around the time you noticed the coolant loss?

 

[flintknapper]

I checked the overflow bottle and all the hoses: no leaks. The level of coolant into the bottle is the same when I checked it few months ago.
Could leak derive from gaskets of water bypasses under the manifold assy intake?

There is only a hard pipe under the intake manifold (runs the length of the engine V) so not likely your trouble spot. However, the rear water bypass is known to leak at either of the gaskets and also at the base of the bypass where the pipe (press fit into the base) goes up to the heater hose.

Since it is at the very back of the engine (behind the intake) it is difficult to see leaks there and those leaks tend to drip off the back of the engine and onto the transmission where they simply evaporate.

Another source might be a 'pin hole' in any of your coolant lines. They don't drip or leak when the engine isn't running, but will leak when the system is under pressure.

IF you have Toyota Red coolant...it tends to leave a crusty pink residue at leak sites, look for that.

But...the best method to find a leak is to pressurize the cooling system and then do your search.

Example of pressure testing for leaks:

Example of a rear bypass leak:

 

[baltistyle]

So per my post, that is the front cooling (water bypass pipe, thank you for the reminder) tube and there is one that looks just like that in the rear. Hopefully from the pics, you have a new place to look.

 

[hoser]

Could also be the radiator cap. If you have no way to test it and you don't know how old it is, just replace it. It's a maintenance item.

 

[abuck99]

If external leaks of that magnitude 13oz per 1600miles there would be visible evidence- wouldnt be hard to locate.

1st thing in morning before start (cool for 8+hrs) , open radiator cap and check level- it should be up to top of neck- around overflow outlet. If the level in your overflow doesnt change- hot or cold- cooling system is still low on coolant

 

[Tres Toys]

I had a similar coolant loss mystery with one of my LCs and it ended up being a water pump that was going out. The water pump is hidden on these vehicles, but if enough coolant is coming out over time it may leave some tell tale traces below it. In my case the water pump that went out did not have all that many miles on it.
Best of luck.

 

[flintknapper]

I had a similar coolant loss mystery with one of my LCs and it ended up being a water pump that was going out. The water pump is hidden on these vehicles, but if enough coolant is coming out over time it may leave some tell tale traces below it. In my case the water pump that went out did not have all that many miles on it.
Best of luck.

^^^^

Water pump IS another possible source. Though generally, you'll see some amount of coolant leaking from the 'weep hole' in the timing belt cover just below the crank pulley/harmonic balancer. You have to look for it, but with as much coolant as the OP is loosing....his would be evident.

Thankfully with water pumps...they tend to 'soft fail' (go out slowly) but certainly a bad deal if they seize.

 

[94SRUNNER]

I too have experienced something similar. In my case it was the upper main coolant hose on the engine side and the top first oil-cooler bypass hose. Both had very minor seeps and was loosing a minute amount of coolant, only notice it over time.