From the Aus forum :-

"I don't know if anyone is aware, but a lot of intermittant coolant leaks are caused by ethylene glycol, the ingredient used in anti freeze, anti boil coolant.

What happens is, rubber hoses shrink, over time, and because ethylene glycol has a molecular size about half that of water, it finds its way out through a slightly loose hose, and murphys law says its the hardest hose to see, and to get to, and depletes the cooling system, of up to the concentration of the glycol, normally 30%.

 

This then, can cause the car to overheat, and loose more fluid.

 

The upshot is, when the radiator is then refilled with plain water, it doesnt leak, because the gap in the hoses, is too small for water molecules, (which may be fine BUT you have no anti freeze, or anti corrosion protection), and then may leak again when refilled with coolant.

 

One of the characteristics of this, is a strong smell of glycol (because this is the only substance leaking).

 

Try going around all the coolant hoses, and tightening them.

 

This may not be your particular problem, but is worth a try."

 

http://216.119.125.120/forum/index.cfm?action=getMessage&message=23510&forum=1

 

Food for thought ...

hmm, ours has a habit of dumping loads of coolant after a long run, well actually not loads, but enough to let you know its droppign some. Comes from the front passenger side, im presuming from the expansion tank, I dont worry If the coolant goes down put some mroe in

I'm not into the black art of fluid dymanics or the specific properties of chemicals but, I use Comma Coldstream premix in my Zed and the temp guage doesn't move under any driving conditions, just sits squarely in the middle of the gauge.

 

Comma Coldstream uses a fully synthetic formulation of Mono Propylene Glycol as opposed to Mono Ethylene Glycol, don't ask me if the mollecules of Mono Propylene Glycol are any larger than its Ethylene contapart but it might be worth a try.

 

Here's the link to the comma site: http://www.commaoil.co.uk/afc.htm

 

I hope this is of some use.

 

Tim

This is exactly whats happening to my UK spec Z (91)

 

Fill with water and no problem,

 

Fill with glycol/coolant and you can be guaranteed she'll piss it all out within a day or two.

I though about the above theory but it sounded too ridiculous to be true.

 

Maybe not so afterall.

Yaaay, I got the same prob. I've been getting a bubbleing sound after engine is shut down. Overheated on Sun. Steam seems 2 b explelling on nearside of rad, filled up with water, happened again.Daft question, but do I put coolent straight in rad? Or the expansion??

 

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after a bad coolent leak the car has mostly just water in it the temp needle still keeps in the middle the car seems not to cool down as quickly after stopping for a while , is this bad, or should I just leave it alone? even if the car shows that the temp needle in the middle could it still be overheating?

Yeah same problem guys. After a good run the car pisses coolant out near the expansion tank. The car also suffers from over heating when sat in traffic jams for over 20 minutes.

 

Here's a question though. It's started doing an interesting new thing. Sometimes if I've taken the car for a long run and it's had plenty of air blowing through it to cool it, I park it up and the temperature is fine, no nasty bubbling noises and no coolant puddles. Then when I come back to it after five minutes and turn the ignition on, the needle's hovering just below the overheat mark. If I start the car, it runs the same as when it is overheating (i.e. sluggish and unresponsive).

 

What could cause the sudden change just by leaving it alone for a bit?

 

Cheers

 

Mike

Mike,

 

Just a thought, when your driving, you'd get air rushing through. When the car is parked up, the hot air from the engine has no where to escape. I had a bonnet scoop fitted and was amazed how quickly my engine cools down now.

 

Vijay

 

[This message has been edited by vijay (edited 01-08-2002).]

Good point Vijay but, surely, the engine isn't producing any heat anymore, just disapating what is already in there.

 

No matter what the air flow is, surely it can only get cooler. Bonnet vents, etc, should should make it get cooler faster.

 

As always, don't know what I'm talking about so I'll apologise now for being wrong!

 

Cheers

The saga continues, lol.

Ive just filled mine with coolent, took her out 4 a quick spin, popped the hood.

She is now leaking from somewhere down on the driverside of the rad, cant see from where tho. So now 2 puddles on floor ?!?!?!

Got a service booked 4 2morow, i'll keep u posted

 

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got the same prob, by the drivers side seem s to be coming from the side wall of the rad

rob

Same as Rob.

Just flushed and added some rad cleaner, gave her a quick spin, now I've got a definate spurt coming from the side wall just underneath the 1st pipe.

New rad?!?! Helppppp

Just got back from a shortish drive, got a definate spurt out of the side wall, driver side of my rad. Just underneath the 1st pipe.

Damm, i've a feeling a new rad might be needed, any1 got any ideas?

Hello Biggybawz,

 

Have a look at this thread: http://www.300zx.co.uk/forums/ubbforum/Forum1/HTML/007274.html

 

Vijay

Nice one Vijay, your a star, i'll mail mac1

The problem with Mike Duffys car is called Heat Sink. It is why, IMHO, we use turbo timers.

I've got this problem too.

 

I was told the following by the AA guy who rescued me last time it badly boiled over...

 

When you switch off the engine the coolant is no longer circulating and there is no air passing over the radiator to cool the water.

The engine is still red hot but the water is no longer being cooled so it starts to heat soak and get hotter and hotter.

If it boils over you probably won't notice as you are well away from the vehicle until the next morning or whatever by which time the steamy puddle has evaporated.

Next day you set off with less water and it all starts all over again only worse cos there's less water in the rad.

 

Apparently it's quite common for there to be a split/leak in the expansion tank or a loose overflow pipe from the radiator cap.

Also a faulty radiator cap that is releasing too early will not help.

I eplaced my cap a while back and it was fine for 4 months but started again. They are only £7 so worth swapping.

 

I'm going to check this lot out when I fit my new intercoolers.

 

...I've just come back from France with the same problem - I was wondering if it could be the radiator cap not sealing in the coolant so that under pressure it dumps it out through the overflow pipe on top of the rad - hence the puddle front passenger side. The rubber disk on the radiator cap seems a little brittle and has some uneven edges - 1990 Jap na.

 

good luck

 

Jack

I've had the same problem aswell!

 

Mr Duff noticed that my top rad hose was shafted at the GPS meet so that has been replaced along with the viscous fan.

 

Mine is still losing coolant but no longer overheating and before when I had the problem the cooling system wasn't even pressurising.

 

Have new Blitz rad cap aswell but don't think there was anything wrong with the old one.

 

I must admit I did have alot of anti-freeze/summer coolant in my system, maybe too much to be honest.

 

Would a hose problem also show fizzy bubbles with the rad cap off and slight revving?

 

Somebody told me recently that is the early signs of HG failure but AA have sniffed for zorst gases in the coolant and SE pressure tested my system while they were sorting overheating problem out and said the system was OK.

 

Can somebody swap my 4hp Honda mower engine for my Z engine? Would be more reliable! FFS!

 

 

 

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i have had a new rad and all new water hoses when the engine was built, and today i had a puddle under the car after having some turbo fun. Went for another drive and all is fine noleaks. I guess when its hot like this and the engine is switched off it generates more heat for a short time as it is not cooling, this may cause the overflow to release some water due to expansion. just a thought.

 

steve

Did you have the a/c on ? You typically get condensation drip out from the back of the engine towards the passenger side afterwards - this is perfectly normal.

My understanding of turbo-timers, or not switching engine off immediately after stopping, is to allow cooler oil to be pumped over the turbo shafts which will be very hot after spinning very fast. This helps to dissipate their heat and stops the narrow shafts from overheating any local oil and eventually causing coking up of the shaft and blowing of the turbos when the shaft cannot rotate freely.

 

Running your engine when not moving should actually make your overall engine hotter, as you don't have the cooling/flow advantages of cooler air rushing past the car/into the fan. The heat sinking mentioned above is probably worse if anything after using a turbo timer. The engines are designed to cope with this, but I think there should be vents in the bonnets as standard to allow hot air to escape easily from under the bonnet. My worry here is that this could? allow water to get into the engine, and we know what problems this could cause !!

Originally posted by AndyP:

Did you have the a/c on ? You typically get condensation drip out from the back of the engine towards the passenger side afterwards - this is perfectly normal.

 

Andy, no i didnt have the a/c on, checked the water this morning and there ws about 500ml missing, topped it up let it run with the cap off, just to check for air blockages and the water just rose and came back out ofthe car, so i put the cap on while it was full and then drove it hard and no water came out, i wouldnt be suprised if it is to do with the hot weather, but i'm no egineer,

 

steve

yep my car did the same today. Think i get a new cap and see if that helps

 

jay