Guys,

 

In the latest of my issues with the most unreliable car in the world, the 300ZX, I still love it though......well anyway, I seem to lose water like theres no tomorrow, it isnt running under the car as Jeff @ Zedworld has had it up on the ramps and he cannot see where the water is going. He fitted me a new higher pressure cap to see if this helps but two days later, I had to put 4 litres of water back in.

 

Help guys, where the hell is it going, jeff says theres no signs of it leaking from the engine and no signs of where its been dripping?!?!??!?!?!!?!?!?!?

 

I can fill it up, go for a drive and everything is fine, but I dont own shares in anti-freeze firms so its no use really!!!!

 

Where can I look next? I havent checked under the floor mats yet?!?

 

Couldnt I have the water system pressure tested????:confused:

You should not be losing water!

 

Have you looked under the car while it's idling?

Possibly a small leak when the system is pressured

that does not show otherwise.

 

If there is no sign of it leaking from rad, pipes or joints

then it sounds like it could be leaking into the cylinder/s

and so exiting via exhaust.

 

Unreliable? don't think so.

I also had a serious water leak I couldn't find (no drips etc) When I looked very carefully at the bayonette fixing for the rad cap I found one of the plastic flanges had worn away enough so that although it looked like the cap was on properly it allowed the cap to move a bit when the engine was up to temp/pressure. It was a real bugger to find as it would only lose water when it was on a run, not when just dawdling aound in traffic. I've now got a replacement rad from the States which is all metal construction, no more of that shitty plastic, and I've not lost a single drop of water since.

 

Might be worth checking that out.......good luck!

When i got my Z 3 years ago i had the same problem. The car could run for weeks fine then all of a sudden would start to overheat. Also when up on the ramps there was no visible signs of a leak. It turned out to be the water pump on mine as after about a year and a half of this problem it finally gave up on me while coming down the M6. Since replacing the pump everything has been fine.

My bet would be the two hoses under and to either side of the top water connection. I find that you get a small split in one that only lets go when good and hot and it heals up again when the engine is running cool. However the water trickles down on the fan pully and gets spun away.

 

Small makeup mirror and torch to look under the top conn when hot and engine off!

 

Also feel top hose for pressure - if soft when hot then you have a pressure leak somewhere.

You may laugh but I've found a leak before by removing the rad cap, putting my mouth around the hole ;) and blowing hard - in my case water sprayed out of the lower side of the top rad hose :)

 

You cant get big pressure because the air bubbles through the expansion tank, but you can get enough.

 

Though if you could get hold of one of those compressors complete with Nissan rad cap, it'd be easy.

 

Pete

Originally posted by pete shrimp

You may laugh but I've found a leak before by removing the rad cap, putting my mouth around the hole

 

 

I wouldnt blow any ones pipe thank you ;)

My leak was on the radiator core, was doing about 1/2 litre in 15 miles. Trouble is it was very difficult to spot because the rad was always hot when under pressure and the water evaporated almost instantly. Eventually I found it, but the give away was the smell of hot anti-freeze (a bit like curry) after a drive.

Put a load of newspapaer underneath the engine and leave it running for a long time, the stains will tell you where the leak is from!

 

Another test for the head gasket is to leave the rad cap off and the engine running, if you see a continuous flow of minute bubbles, the size of the ones of a side of a glass of lemonade! Then you might have problems:(

Another simply idea is to add some food dye to the coolant - it should then deposit a coloured trail for you to follow back to the leak...

Thanks for all your thoughts guys. The coloured dye sounds like an idea, any ideas as to what I could use??

 

Also, do you know anywhere where I can get the colling system pressure tested around Northampton area? I dont mind travelling.

 

Jeff @ Zedworld said he had it up on ramps running for 30mins but couldnt see anything obvious, he also went for a long run, bought it back and also checked but nothing.

 

I think this is going to be something similiar to Andy's problem, the water is obviously evapourating before it gets chance to leave a trail which isnt helping the fault finding.

 

Mmmmm, well, the rad cap and radiator are only 4 months old, well the cap is brand new, and it only dissapears when its under pressure. I presume the water pressure increases whilst driving??

 

A rolling road would be useful but then that could get expensive to hire one to find the fault.

 

Well, my other halfs dad is going to have a look with me at the weekend so I will let you know how I get on.

Most garages will have a coolant pressure tester thingy - I got a freebie from the village garage owner. Well, not quite free, it cost me a pint. :D The nice man from the RAC had one too last time I overheated. They're also not that expensive if you're desperate and you could probably flog it again on eBay or something...

 

Like someone else said, you can smell it - I thought it was just how these engines smelt until I found the jubilee clip that was leaking. It smells a bit like curry or more like fenugreek in particular, I personally think. I had a tiny tiny leak but as soon as I pulled it into above garage the owner said "it's leaking, that, I can smell it." Woulda thought therefore that Jeff would have done too.

 

Pressure certainly does climb whilst driving - a) the pump is running and b) it's hotter and heat -> pressure in fluids.

 

If it's under pressure almost straightaway - ie you run the engine with the rad cap off and it spurts after a minute or so - it's your gasket. Don't run the engine for any more than that without the cap on though!

 

Also look for water in oil (take oil filler cap off when cold - you'll see "mayonnaise" brown emulsiony stuff which is a mix of oil and water) or the reverse, oil in the coolant.

 

Probably just a split pipe somewhere though, esp since it's cold weather now - that'll have finished off whichever pipe was rotten.

Hi Zevans,

 

really useful reply that, much appreciated!

 

Well, I diddnt go over th ecar with the missus dad but I have been using it and even after 30mins of driving, I've lost a few pints??!?!?

 

Obviously, when I go to fill it up b4 driving again, I start the car and I do see loads of bubble, but they are smnall and big, then if I keep filling up, after about a minute they all dissapear and then I get the odd large bubble. So, presuming the water system is full, I put the rad cap back on and off I go and then have to go through it all again.

 

I really thought Jeff would have found something and I probably aint gonna get chance to have a look this weekend. Need to get some work done on my fiesta!!

 

If it is a head gasket, but then I guess the bubbles would have continued, would I have to replace both head gaskets?? I Presume theres two! And would it be hard for me to do it!!

just had the same problem and found a small split in one of the hoses between the engine and window bulkhead, I think it was for the heater, its a twat to get to but had to pull it off the pipe and trim it back an inch and replace, since then its been fine. Mine didnt drip until the split became quite big then it was easy to see.

I've got the same problem on mine - no sign of water coming out (aside from the a/c overflow pipe) when idleing, but losing water during a journey.

 

Poured radweld in, can smell it when the car is hot but I simply cannot see where it is coming from.

 

Guess I'm going to have to start tracing hoses etc - anyone got any pointers as I'm new to the 300zx

If you can smell it in the car then your heater is most likely leaking.

Lift the carpet and see if it's wet.

Not very likely to be the gasket by the sounds of it - no temperature problems and those bubbles sound more like it's leaking somewhere...

 

Best thing you can do is get hold of a pressure tester!

 

I found one leak on mine just by going around fiddling with clips I could get at - one of them was obviously loose. As it turns out it was that leak that had hidden the real problem of the gasket...

Well I am gonna have a good luckover the weekend and see what I can see.

 

Loads of power still there, no water in oil, no smoke coming out of exhausts so I am guessing a leak now.

 

I will download some of the manual and check what I can.

 

Wish me luck!!:)

It could be a head gasket causing water from the coolant system to leak into the oil ways or into the combustion chamber

 

check your oil level if the car is 'making oil' then water is most likely leaking into the oil

 

if not check your exhaust for excess vapour/steam this is a give away for a blown head.

 

with the engine cold, open the radiator cap and start the engine, then look in the cap opening and see if you see a excess of gases bubbling up to the opening, this could be a sign that combustion gases are getting into the coolant sytem, also a blown head gasket giveaway.

 

also when you are checking you car for water leaks..run it till it is at normal running temp with the radiator cap in place, this causes the coolant system to be under alot more pressure and you more likely to spot a leak.