Spoke too soon.

[Phil]

Been watching my coolant like a hawk since replacing my t piece and hoses. I have observed that if I drive the car with the heaters on hot then switch the car off overnight, the coolant level would be just over max in the morning, but if the heaters were set to cold then the car left overnight the coolant level would be below maximum the following morning. Anyway, today I checked my coolant level and I'm very disheartened to report the level is dropping again. I just don't understand it, I've got no leaks now, the cooling system isn't pressurising as far as I can tell, there's no mixing of oil and water, no excessive steam from the exhaust, the car has done nearly 49,000 miles and never had HGF, a lot of other posts I've read on .org have a lot of owners reporting it a lot lower milages, and I'm starting to wonder if this is the early stages of a hgf, bearing in mind it looks like an easy job to do the head gasket, do you collective brains think it's the most probable cause of my water loss and worth while me just doing the headgasket? I know its a bit premature but I'm at a complete loss.

I do have a gurgle that comes and goes from time to time from the heater matrix, I did half wonder whether there was an airlock that is slowly working its way out, that would explain the water level dropping, the gurgle has been there for ages, but if there is an air lock, it must have got in there some how in the first place.
:( :( :( :( :( :( :( :(

[GreyGhost]

Hello Phil
I seem to recall from an earlier post that you refilled using a non proprietory method. Would it be possible to do the coolant refill using the correct vacuum tool? Have you changed the rad cap?
I know you know your way around a car, just trying to dot the I's and cross the t's. Any chance of a tiny leak onto exhaust manifold steaming off before notice, or possibly the heater matrix where you can't easily see.

Best of luck with it, hope you turn up the answer soon.

[Phil]

I used a method we use on the Honda's, which consists of a huge funnel that sits at a higher point than all the other points on the cars cooling system, I also measured what I drained out so I know I got the same amount back in, I haven't got access to a vaccuum tool and even the Rover dealer here said they have never used it. They are nearly £100 on ebay so I'm reluctant to buy one. I was wondering, does anyone know if the heatermatrix lies flat or stands up on one end, if it stands up I was wondering about disconnecting the pipe goin in, assuming its at the top of the matrix, attaching a funnel to the hose going in and tipping antifreeze directly in to hopefully displace any air. If that makes sense to anyone?! The gurgling has been there since I had the car. And it has been loosing coolant slowly since I have had the car, 10,000 miles. I've already tried a new cap.:(

[Mike]

Here's a pic of the matrix (in red box) from the drivers footwell - as you can see it sits behind the centre console just forward of the foot vent. The feed in pipe is the bottom of the two , the out pipe at the top. Second pic shows the matrix from the other side.

I am currently writing a how to for removing and clearing out the matrix as when it blocks up it prevents warm air from being fed to the passenger side. If the rough text will help you now then pm me an email and I'll forward it.

Pictures courtesy of Stephen

Mike :)

http://www.the75andztclub.co.uk/forum/imagehosting/94564a93718cd8.jpg

http://www.the75andztclub.co.uk/forum/imagehosting/94564a969e77ac.jpg

[Phil]

Hi Mike, looking at that there can't be any air in it cos I'd have cold blowers. Doh. Bang goes that theory. Is this gurgling noise normal on a 75? I remember reading several reports on .org. By the way, thanks for the photo's.

[Phil]

Has someone got an explanation for this? Last night, I took my cap off when the engine was still hot, the water level went up about an inch over maximum, and this morning when the engine was stone cold, the level had gone back to where it should be! Without me putting any water in it! Whats going on!?

[GreyGhost]

Has someone got an explanation for this? Last night, I took my cap off when the engine was still hot, the water level went up about an inch over maximum, and this morning when the engine was stone cold, the level had gone back to where it should be! Without me putting any water in it! Whats going on!?

Hot liquids expand, hence pressure cap to allow any excess to escape if overfilled.
If I remove cap from mine when the engine is stilll warm not hot. a small amount always overflows. Back to normal when cold.

[Phil]

I meant that the morning before I took the cap off, when the engine ws cold, the coolant level was below max, but when it was hot and I removed the cap, the coolant level went up about an inch, but it didn't drop below max the following morning when it was cold. Does that make more sense?

[GreyGhost]

I meant that the morning before I took the cap off, when the engine ws cold, the coolant level was below max, but when it was hot and I removed the cap, the coolant level went up about an inch, but it didn't drop below max the following morning when it was cold. Does that make more sense?

I words make perfect sense, the coolant levels do not, sorry can't help :(

[Simon]

Just to correct some technical errors: ;)

Fact #1: Liquids neither expand when hot nor do they shrink when cold.

Fact #2: Chemicals in a liquid may gain enough energy when the liquid is heated to cause the chemicals to turn into a gas. This could cause the overall liquid level to appear greater when it's hot. These bubbles will (most likely) re-disolve when the liquid cools.

Fact #3: I know these things. ;)

[Phil]

I meant that the morning before I took the cap off, when the engine ws cold, the coolant level was below max, but when it was hot and I removed the cap, the coolant level went up about an inch, but it didn't drop below max the following morning when it was cold. Does that make more sense?

Just to correct some technical errors: ;)

Fact #1: Liquids neither expand when hot nor do they shrink when cold.

Fact #2: Chemicals in a liquid may gain enough energy when the liquid is heated to cause the chemicals to turn into a gas. This could cause the overall liquid level to appear greater when it's hot. These bubbles will (most likely) re-disolve when the liquid cools.

Fact #3: I know these things. ;)



Right then smarty pants;) Could you explain my water dropping then reappearing miraculously:p: ??!

[Simon]

Right then smarty pants;) Could you explain my water dropping then reappearing miraculously:p: ??!

Err.. I'll get me coat... :o

[Simon]

Could still possibly be an airlock in the system tho. This would explain why the level appears higher when the engine is hot (as the air has expaned).

[Phil]

:lol: I wish I could explain it. Hey ho.

[Phil]

Could still possibly be an airlock in the system tho. This would explain why the level appears higher when the engine is hot (as the air has expaned).

Thats what I thought, but would that explain why the level gets low when the engine is cold, then when the car is hot, removal of the cap will raise the coolant level and it will remain at maximum when it cools down again, without adding any coolant.:confused:

[Simon]

Thats what I thought, but would that explain why the level gets low when the engine is cold, then when the car is hot, removal of the cap will raise the coolant level and it will remain at maximum when it cools down again, without adding any coolant.:confused:

It could do, yes.

Bear with me on this explanation as it could get a bit confusing. Here go's:


When coolant is cold, air bubble is small which would make your coolant look low on the reservoir.

When the engine (and therefore the coolant) is hot, the air bubble is larger due to expansion hence your coolant level looking normal in the reservoir.

When you take the reservoir cap off with the engine hot, the pressure between the coolant and the outside air will slowly equal out meaning the air bubble could remain at its larger size (ie, it doesn't shrink in size because the liquid in the system has somewhere to go in that it can move freely in the reservior).

With the cap on the system, pressure of the coolant can force excess air out of the system (at a weak point) but then the sytem cools, it leaves a kind of vacuum and so the air lock 'shrinks' back to it's 'normal' size.

This explanation may seem a bit long-winded but the principles of physics at work here do seem to suggest this as a possible theory.


Anybody any thoughts on this?

[Phil]

I think I know what you mean, I wonder if these air bubbles are likely to work their way out. I noticed yours is a ZT 160, is yours a V6 or a 1.8t?

[Simon]

I think I know what you mean, I wonder if these air bubbles are likely to work their way out. I noticed yours is a ZT 160, is yours a V6 or a 1.8t?

I've got the V6 so my coolant system has more capacity. From what I gather on these forums, the coolant system in the 1.8T is a much smaller capacity and more prone to coolant-loss problems due to there simply being less of it to start with.

I suppose this could in theory happen on any car or any plumbing-type system it just seems that (unfortunately) on the 1.8T it can lead to badness. :(

I also remember reading that if you do not have access to a vacuum-pump for the refil of coolant then you can use another method which involves (i think similar to how you originally filled it...) filling the sytem and then running the car for at least 20minutes whilst slowly manipulating the hoses to help work out any air bubbles.

I suppose (if you haven't already done so) is try the idle for 20min while easing the hosing.

If all else fails then it may be a case of finding a garage with a vacuum-filling sytem to flush through the coolant system.

:lol:

[Sting]

Just to correct some technical errors: ;)

Where it says fact read "Urban Myth". :D
Fact #1: Liquids neither expand when hot nor do they shrink when cold.

Of course they do. Some liquids actually expand when cooled, within certain ranges. Water has its maximum density at 4 degrees Celsius, for example. This is why ice forms on the top of lakes rather than at the bottom. What happens when you fill your ice cube tray to the very, very top? Where did all that extra ice come from? Liquids are generally incompressible at a given temperature, which, in part is the definition of a liquid.

Fact #2: Chemicals in a liquid may gain enough energy when the liquid is heated to cause the chemicals to turn into a gas. This could cause the overall liquid level to appear greater when it's hot. These bubbles will (most likely) re-disolve when the liquid cools.

All liquids will turn to gas at a characteristic temperature and pressure. Gas occupies more space than the liquid phase at the same temperature. Certainly a boiling pot of water has its surface at a higher level than the same warm pot.

Fact #3: I know these things. ;)

Really? From where?

[stocktake]

Five years for a correction, brilliant :D :D :D

you are however correct ;) ( you should have joined earlier ) :D :D

[Sting]

Something inside me just said, "You're here to get a question about a heater matrix answered, but you just can't let this post go..."

[James.uk]

We didn't want to upset Simon Dave.. ;) :D ...
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