Weird coolant loss behaviour (1 Viewer)

[AtinLango]

When i do long trips of about 300 miles nonstop (which i do regularly), my engine coolant level (measured after overnight parking) remains exactly the same. This means a round trip of 600 miles.

When i do short town trips, my engine coolant level (measured after overnight parking) drops slowly but surely, and becomes quite noticeable after some weeks. I do not need to keep toping up because it is a slow loss, and the level may only reach midway after some months.

This has been the status for the last six years. At one point, i nearly declared that the problem was solved after replacing a hose pipe, but i was weong.

Note that i check coolant level at exactly the same spot in my garage, and only after the car has cooled overnight.

Everyone says it is a head gasket issue, but it does not make any difference when changed.

I use the red Toyota coolant only.

Inspite of this issue, i have no problem deciding to go on a trip even now, i can just start the car now and drive 300 miles (or perhaps 500 miles) nonstop.

What could be the science behind this weird phenomenon?

 

[efjayatee]

On the fzj80 the rear heater hose leaks over time...(maybe?)
Not sure if it applies to the 100s

 

[awesomeissquid]

On shorter drives is the engine getting up to full operating temperature? I wonder if they are short enough that something loose is letting a slow amount of coolant to leak past. Then on longer drives it warms up and swells and stops the leak.

If it is external you should see pink crusties around the leak area to identify. Get a flashlight and start tracing the cooling hoses and check over the full engine. Don’t forget about the rear heater hoses that run above the DS cat.

 

[AtinLango]

On shorter drives is the engine getting up to full operating temperature? I wonder if they are short enough that something loose is letting a slow amount of coolant to leak past. Then on longer drives it warms up and swells and stops the leak.

If it is external you should see pink crusties around the leak area to identify. Get a flashlight and start tracing the cooling hoses and check over the full engine. Don’t forget about the rear heater hoses that run above the DS cat.

Yes, on short drives, the engine gets up to operating temperature. The shortest drives for my landcruiser are about 3 miles, but these are very rare because i use another smaller car for such drives. The average short drives for my landcruiser are 10-30 miles. I do not allow to drive and stop when engine has not reached operating temperature.

We do not seem to see any dry pink crusts. However, i used to see some at the end of a small pipe attached to the firewall somewhere close to and above the oil filter level. In hindsight, this could easily provude a clue to my problem. AND OH YES, i replaced that pipe about 4 years ago, but there was no change.

 

[2001LC]

Checking in morning in same spot in garage, is great. But temperature is key. Level change with OAT also.

1. Look under radiator cap. Make sure all the way to top during cold morning. Any air gap, reservoir will not work properly.
2. Reservoir hose must drop straight (don't get hung a curl up, on shelf) down and hose and it's cap be free of obstructions.
3. You must have good thermostat, jiggle valve up.
4. If you need to add fluid in radiator today, check again tomorrow.

Some minor evaporation happens with time. But it should not be much.

Edit 1/1/25

Radiator fins need cleaning! Alert Alert Alert

I've a 06LC w/192K I just bought. In reading history I found PO complained of engine temp raising when both front and rear AC on. Toyota Dealership diagnosed with clogged radiator fins. Recommended new OEM radiator, $600 for the US spec Radaitor plus coolant and labor. They should have added...

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[Bisho]

I had a similar issue on my 100 that was driving me nuts. I finally found some pink under the heater Ts, but couldn’t see a leak. Turned out when truck was first started the hose leaked going into the firewall (the hoses and constant tension clamps were only 4 years old ~70k miles). I fished a worm gear clamp on it and leak is stopped.

 

[AtinLango]

I had a similar issue on my 100 that was driving me nuts. I finally found some pink under the heater Ts, but couldn’t see a leak. Turned out when truck was first started the hose leaked going into the firewall (the hoses and constant tension clamps were only 4 years old ~70k miles). I fished a worm gear clamp on it and leak is stopped.

Interesting. For me, also everyone has failed to find a leak anywhere for all the past years.

 

[AtinLango]

Look under radiator cap. Make sure all the way to top during cold morning. Any air gap, reservoir will not work properly.

There is a small air gap (very small, but it is there). The tip of the cap just touches the coolant. If i try to top up at the radiator, just a few drops go in before overflowing. I was concerned about this at one time, but somehow people thought it was okay. When I open the radiator cap, coolant does not spill out because it is not too full.

In another Mitsubishi diesel car that I have, the radiator is full all the way. There is no gap at all for air. When I open the radiator cap, coolant is too full and some spills out.

You must have good thermostat, jiggle valve up.

My thermostat is good. In any case, I replaced it a number of times before in an attempt to solve the problem.

If you need to add fluid in radiator today, check again tomorrow.

There is no need to add today. I usually add after 6 or so months after the reservoir level is reaching midway. Sometimes even after one year. I always check the level at a microscopic scale.

 

[efjayatee]

There is a small air gap (very small, but it is there). The tip of the cap just touches the coolant. If i try to top up at the radiator, just a few drops go in before overflowing. I was concerned about this at one time, but somehow people thought it was okay. When I open the radiator cap, coolant does not spill out because it is not too full.

In another Mitsubishi diesel car that I have, the radiator is full all the way. There is no gap at all for air. When I open the radiator cap, coolant is too full and some spills out.


My thermostat is good. In any case, I replaced it a number of times before in an attempt to solve the problem.


There is no need to add today. I usually add after 6 or so months after the reservoir level is reaching midway. Sometimes even after one year. I always check the level at a microscopic scale.

When the last time you flushed the radiator? I do once every 2 years.

 

[AtinLango]

When the last time you flushed the radiator? I do once every 2 years.

Just close to 2 years ago, but this issue has been there before and after flushing.

 

[AtinLango]

Just noticed a tiny pink deposit around the coolant reservoir (overflow) cap. I notice also the cap was not fitting tightly enough.

Some years ago, I had changed the reservoir cap in pursuit of a solution to the coolant loss issue. That never helped.

So i have just put back the original reservoir cap, and it fits tightly.

I am not sure at all that this will change anything. I will wait to see.

 

[2001LC]

I'm not sure you are loosing coolant. Keep in mind, we do have some evaporation. Also, the outside air temp (OAT) matters. On a hot day, after engine has cool for 8 hours. Level is higher than on a cool day coolant.

If you're sure you are leaking?

 

[AtinLango]

I'm not sure you are loosing coolant. Keep in mind, we do have some evaporation. Also, the outside air temp (OAT) matters. On a hot day, after engine has cool for 8 hours. Level is higher than on a cool day coolant.

If you're sure you are leaking?

I am very sure i am losing coolant. Like I said before, i have to top up after 6 or so months as the level will have dropped by about a quarter, or towards half. If i drove mostly short trips for over one year without topping up, i am sure the reservoir level would be below midway.

On short runs, i can see very minute, hair-liine drops after some days. But everybody else would say there is no drop. I know better since it is my car.

Very clearly, there is coolant loss.

 

[efjayatee]

What parts have you replaced? You mentioned thermostat, rad cap and hose to the firewall......
What yr of vehicle and miles would also help. Also what brand of coolant is in there?

Get a scan gauge and monitor your ECT would be the 1st thing I would do.

 

[AtinLango]

What parts have you replaced? You mentioned thermostat, rad cap and hose to the firewall......
What yr of vehicle and miles would also help. Also what brand of coolant is in there?

Get a scan gauge and monitor your ECT would be the 1st thing I would do.

Toyota Landcruiser Amazon, diesel, AT, year 2002, 155k miles.

I use Toyota red coolant.

About 3 years ago, two different mechanics inspected but failed to find a leak. Nonetheless, each of them went ahead and replaced head gasket. Infact one of them even replaced the head. This resulted in no change. Just waste of money.

We also replaced thermostat, radiator, radiator cap (several), water pump, some hose pipes ...

If i leave the car with a mechanic for some days, they will say that there is no coolant loss because they cannot see a drop in level. But i can see.

i think it is not a big deal. May be it is just evaporation.

 

[efjayatee]

I just topped off my coolant's resovoir last week on my gen1 sequoia since its rad was flushed 2 years ago. It was at the "low" line

I don't think you should be worried but I would install an external coolant gauge.

 

[AtinLango]

I just topped off my coolant's resovoir last week on my gen1 sequoia since its rad was flushed 2 years ago. It was at the "low" line

I don't think you should be worried but I would install an external coolant gauge.

Actually mine has never reached low line. I usually top up when it has dropped about quarter way in 6 or more months.

I think it would take over two years for It to reach low line.

Other than that, i drive comfortably - so I agree that i do not have to worry about it.

Thank you.

 

[efjayatee]

Actually mine has never reached low line. I usually top up when it has dropped about quarter way in 6 or more months.

I think it would take over two years for It to reach low line.

Other than that, i drive comfortably - so I agree that i do not have to worry about it.

Thank you.

Yep....
It's your OCD got the best of you.