Water loss

[Ian C]

Coolant is just antifreeze and corrosion inhibitors isn't it? It's the pressurisation of the cooling system that ups the boiling point, not any additive.

[Guest Roger NE]

Personally I wouldn't worry too much about just topping up with water UNTIL you have found the problem ! (you're wasting a lot of money) Sure, you need coolant for the corrosion inhibitors and to prevent freezing . . . and it's a slightly better coolant than just water . . . . BUT it wouldn't cause any of the problems in the short term if you just used water.

 

On the Mk3 engine where HG failures are common, I usually suggest running the engine from cold with the Rad Cap off (make sure the rad is fully topped up) . . . . as the engine gradually warms up watch the liquid in the top of the rad as you rev the engine (pull the lever on the Throttle Body) . . . if you have HG failure causing the coolant loss you'll probably see bubbles in the top of the rad.

 

I have had a couple of TINY leaks over the years, caused by a pinprick hole in a small hose that means there is no sign of a leak (ie no drips) yet it was enough to cause the kind of coolant loss you're talking about. I only found it when I removed ALL the small hoses one by one and inspected them off the car. Another more recent one was a pinprick sized hole in one of the Core Plugs (as already suggested) . . . . again no visible sign of a leak!

 

Hope that helps . . . .

[Al Massey]

Coolant is just antifreeze and corrosion inhibitors isn't it? It's the pressurisation of the cooling system that ups the boiling point, not any additive.

 

No, it has ethylene glycol too.

 

http://auto.howstuffworks.com/cooling-system3.htm

[Ian C]

That's what I was counting as the antifreeze The effect it has on the boiling point is fairly titchy, in the OP's case I'd imagine the 6degC difference isn't the margin between him boiling off his coolant and everything being okay. I'd just chuck tapwater in until you find where it's going. My money is out the exhaust due to a BHG if it's not ending up on the floor.

[Al Massey]

That's what I was counting as the antifreeze The effect it has on the boiling point is fairly titchy, in the OP's case I'd imagine the 6degC difference isn't the margin between him boiling off his coolant and everything being okay. I'd just chuck tapwater in until you find where it's going. My money is out the exhaust due to a BHG if it's not ending up on the floor.

 

Yes antifreeze only increases it a few degrees but after pressurisation it increases a lot further.

 

So with out any coolant in, at 100°C the water will boil anyway

 

And if there is a pin hole somewhere it will vent off easier surely :/

[Nic]

Hi all. I have a 1993 non turbo supra vvti and it's using a lot of water. I put a new radiator in and new top and bottom radiator hoses and a new thermostat but it keeps using water. It uses around 2 liters every 3 days or so. Any help or ideas will be welcome thanks

 

NA VVTi?

 

I'd start by trying a new standard radiator cap.

[a98pmalcolm]

I had a leak. And a sneaky one at that. Right at the back next to the bulk head theres a pipe. Not massively visable

Have a look there

[Ian C]

Yes antifreeze only increases it a few degrees but after pressurisation it increases a lot further.

 

So with out any coolant in, at 100°C the water will boil anyway

 

And if there is a pin hole somewhere it will vent off easier surely :/

 

Pressurisation increases the boiling point of water, so as long as the system is pressurised, it won't boil at 100degC. The glycol is mainly there to stop it freezing at 0degC rather than increase the boiling point

 

If the water was boiling you'd see it in the expansion tank, it'd be shaking and blopping water out the overflow pipe. Yes, I once owned a MkIII Supra

 

- - - Updated - - -

 

NA VVTi?

 

 

We've done this bit already, and I'd have thought you'd known better Nic

[Digsy]

Vapour pressure curves for water, 50/50 and 20/80 coolant mixes, if anyone's interested.

 

If there is a leak, it will be harder to build up system pressure so even a 50/50 mix might be boiling as low as 110. Also if the system can't build up pressure then it won't vent through the rad cap properly. Hence why I was trying to diagnose what was going on in the expansion bottle.

[Guest Roger NE]

I don't know if the Mk4 engine is the same, but the Mk3 has a very short J-shaped hose on the back of the head . . . that was the hose where I had my pin-prick leak, and I say it just wasn't visible. (No sign of water drips OR steam, I guess it was evapourating as soon as it leaked as it touched the engine.)

 

Such a small leak never caused me any overheating, as long as I kept topping it up (even though the system obviously wasn't pressurising fully)

 

As I say, I know it's tedious, but I would remove all the small hoses one by one and inspect them - bet you find a tiny hole or split.

 

That's presuming you have FIRST tried the bubbles in the rad test I suggested earlier.

 

(and some of the points made about Antifreeze may be correct, but I think irrelevant to this problem !)