Permanent low coolant level

[Animal Mother]

My 120 (2007 D4D Auto) seems to permanently have a low water level. I top it up to max, but it will always find its way to the low water level and then stay there (it drops below it when hot but finds its level again when cool).

Anyone else suffer from this? I've heard (on one of the LC Facebook groups) of others with it. I've had it sniff tested, new water pump, leak checked etc. All good. Even had a new expansion bottle cap.

Any ideas?

 

[StarCruiser]

No idea why it happens but my 80 cannot keep water in the expansion bottle. It sits around 1/2” below the main radiator cap and that’s where it stays and has done for the 14 years I’ve had it with no adverse effects.

My only thought is whether the radiator cap has been changed for a different type. Or maybe the expansion bottles get porous, but I am really clutching at straws with that one.

I believe @clivehorridge has the same with his 80.

Bottom line is, it’s found it’s own level, monitor it and don’t worry too much. If it was constantly dropping then it may be worthy of investigation but if it stays put I’d say there’s nothing to worry about. Be interesting to hear from those that know more about this than me.

 

[Ben Stratford]

Has the bottle been moved from its original place which could upset things?

 

[foto2021]

We have the same problem with our 2003 D-4D. It was losing coolant through a leaking water pump. Had that changed, now it maintains its level but only at the low mark. Fill it any higher and it disappears, back to the low mark.

 

[Shayne]

My theory is it needs an expansion bottle because the pressure goes up and down with heat , the radiator cap is a pressure release valve , so the balance is between the weight of water in the expansion bottle and the vitality of the rad cap , when the cap is weak it can't fill the bottle so the cap blows off the excess as steam .

If i'm right , and i rarely am , a new cap should allow you to keep more water in the expansion tank .

 

[clivehorridge]

No idea why it happens but my 80 cannot keep water in the expansion bottle. It sits around 1/2” below the main radiator cap and that’s where it stays and has done for the 14 years I’ve had it with no adverse effects.

My only thought is whether the radiator cap has been changed for a different type. Or maybe the expansion bottles get porous, but I am really clutching at straws with that one.

I believe @clivehorridge has the same with his 80.

Bottom line is, it’s found it’s own level, monitor it and don’t worry too much. If it was constantly dropping then it may be worthy of investigation but if it stays put I’d say there’s nothing to worry about. Be interesting to hear from those that know more about this than me.

Mine sits about 1 cm above the fin tubes, but the expansion tank is always on the line...

 

[foto2021]

If i'm right , and i rarely am , a new cap should allow you to keep more water in the expansion tank .

Very good point. After 15 years, it wouldn't be surprising if a new cap were needed. Thanks, I'll try one!

 

[StarCruiser]

I shall be interested to see the result of a new cap.

 

[Animal Mother]

I've a new cap on mine (changed based on the above theory) but it didn't make a difference.

 

[StarCruiser]

I've a new cap on mine (changed based on the above theory) but it didn't make a difference.

But is that a cap on the bottle or the rad? Not sure how the 120 is configured but if it’s like the 80 the main cap is on the rad and only a simple plastic cap on the expansion bottle.

 

[nick_the_fish]

Out of interest how often are you having to fill it up?

 

[Animal Mother]

But is that a cap on the bottle or the rad? Not sure how the 120 is configured but if it’s like the 80 the main cap is on the rad and only a simple plastic cap on the expansion bottle.

Only a cap on the expansion tank on this model.

 

[Animal Mother]

Out of interest how often are you having to fill it up?

It doesn't go below the Low level so no need to top it up. However, one journey of 30-40 mins and it will go from MAX to LOW.

 

[Animal Mother]

Finally an update on this.

When I bought the LC it had a duff water pump. The dealer replaced the pump for a Blueprint item. This solved the significant coolant loss issue that it was suffering.

Clearly this wasn't the full extent of the problem, hence my creation of this thread. It has always been hard to maintain the coolant level until recently, however, there was always a very slight reduction in coolant level more recently.

Fast forward to this weekend just gone. I wanted to replace the Blueprint pump anyway so I bought a Toyota unit to replace it with. This is the full unit (both pieces, rather than just the pump section).

The Blueprint unit had been leaking from new through the weep hole from day one. A slow leak only, hence the issue with maintaining the coolant level. When I removed it, the weep hole had eventually become gummed up with the crystals that get left behind.

Upon removal of the entire pump unit (pump and housing), I discovered that the housing had also a very small leak from the gasket where it mated tot eh engine block.

NEVER buy a Blueprint pump. Stick with OEM Aisin or Toyota.

 

[clivehorridge]

Like @StarCruiser I’ve always in 12 years of ownership, pondered this one and been satisfied that it “finds its own” level. Triggered by this thread, I filled the rad, it took just under 1 liter to brim it. I then drove about 500 km and after a cooling off period overnight, it was back down to its own level, no signs of any leaks and the level in the expansion tank was bang on the line.
What to say?
As an aside note, the water “pump” is only a circulation device, meaning it doesn’t “pump” any pressure within the system. All the pressure is generated by heat and expansion, pressurizing to the limit of the cap spring, irrespective of whether cap is before or after the expansion tank. On the 4.2 diesels, the pressure cap works both ways, retaining pressure when hot, yet when cold (or cooling) allows water to be drawn in from the expansion tank. In theory, the rad should always be brimming, but in practice, it seems to do what it likes!
I have a new (ish) cap on mine, BTW.