Right Just got back from about a 100 mile fast motorway drive, Zed was behaving well until I got home, Whilst Parking it in the garage I could here Boiling and the temp started to rize slightly on the gauge so I put the heaters up full let it run for thirty secs or so then turned it off. I could hear the boiling type sound for about a further 10 mins and there are no obvoius signs of a leak although it was far to hot to check the levels. Any thoughts people?

You should not be able to hear any boiling of the water.

If you can hear what sounds like boiling, it usually means there is a leak or an air lock.

 

Could it not be the AVI?

Um, Whats the AVI???

Air injection valves are under the wings, they send are to the manifold under certain conditions, if not functioning properly they 'gurgle'.

Quoted "Could it not be the AVI?"

 

No the sound was after he had switched off the engine, that will be air in the system causing perculation of the water due to heat and air under pressure.

 

This is not a good situation as it causes localised hot spots in the engine and at worse can lead to warped heads.

 

 

The cause may be little more than low water level, the motorway cruise was most likely providing plenty of cooling air over the engine, but once off the the motorway the low water level had compromised the cooling system.

 

 

Check the rad cap for correct tight fit, the water hoses at the back of the engine, the water hoses adjacent to the throttle body and the two bypass hoses above the water pump and of course the water pump itself.

 

If no problems seem evedent refill the system taking care to get all the air out of the system by putting the heat controls to 40 deg and running the engine (cold) and adding water to both the radiator cap fill point and the small plastic bleed screw on the top of the radiator.

 

Hopefully this will help, for more info post again

 

 

Jeff TT

Just a thought, the sound was coming from near the Expansion tank.

Rightthen, I have just refilled the z with water, took approx 3 litres. Ran her for 30 mins with heaters up full and there are no obvious signs of a leak anywhere, however I noticed a hole just at the bottom of the expansion tank neck, is this ment to be there? Took her for a short drive and all seemed ok but why did she overheat and where did 3 litres of water go with no leak????????? Pussled.

You must have a leak dont trust it mate lol could be a pin hole make sure before you go on a long fast run again.

big air lock maybe in the matrix...hence no water spilt?.....you can try filling the coolent parked on a steepish slope to make any air locks rise to the neck..whilst running the engine and heater etc

Quoted "I noticed a hole just at the bottom of the expansion tank neck, is this meant to be there? "

 

Yes it is standard. The missing water could have crept up on you over a period of weeks or so until it was more critical.

 

As said previously a poor seated rad cap releases pressure, and as a result the boiling point of the water will reduce to its non pressurised figure, steam can then vent whilst you are driving, this is less noticable over time this adds up to more and more water loss.

 

Do do as many checks as possible though because the major cause of broken zed engines is overheating / temperature related.

 

Jeff TT

There was deffo no steam coming out of rad cap and it seems to fit well.

 

Thanks for the advice all, here is my plan: a) Its due a cambelt service in bout 5k, just gonna get it done now along with water pump, thermostat etc. b) I know that as soon as I take my rad pipes of they will probably take half the rad with them so will replace the rad. c) Already have a smitthy top hose (Fitted) and a silicone bottom hose to fit.

 

If that fails to cure the problem what do I try next???

Right I have now spent the last four hours stripping of the fan shroud, all undertrays etc, taken her for a long hard ish drive and guess what, no water loss, no overheating, infact seems to be running really cool!!!!!!!!! What the hell is up with it, I just wanna find a leak to fix or something. Any Ideas anyone????? Im lost as what to do next.

UPDATE: Right took her for a hard drive and when i got back could see water coming from the bottom of the expansion tank once I had been stopped a few mins. Have removed the tank but cant seem to find a hole and is certainally not leaking now. Could there be a small hole in the tank that only leaks under pressure? Should I just replace the tank and hope the problem goes away????

Bump

try swapping the radiator cap with another one (one that is known to be working good) and see if the problem dissappears.

 

If not, the system is building up pressure because of an airlock, which can be caused by a small leak in one of the coolant hoses or a small leak in one of the headgaskets.

 

-Eric

I have noticed a few people with water leaks from the rear hoses that have pin holes in but dont really leak but vent steam whilst being driven thus the steam just blows out under neath the car whilst driving and when you slow down or stop the leak,steam stops but you slowly and descretly loose water causing overheating and bubbling water.

try swapping the radiator cap with another one (one that is known to be working good) and see if the problem dissappears.

 

-Eric

Sounds like a radiator cap, try and disconnect the tube going into the expansion tank and see if it leaks while the engine is cold or slightly warm, that was my problem, anyway.

um, disconnect the hose to the expansion tank from the top of the rad (got that bit), where do I then look for leaks?

um, disconnect the hose to the expansion tank from the top of the rad (got that bit), where do I then look for leaks?

from the hole you just pulled the hose off ;)

Popped to halfords and found a rad cap for a nissan 200sx, only £3 so I bought it to try. Seems to have sorted the problem. Now I know its the cap I will buy a new OE cap. Thanks for all your help guys. Hard to believe a rad cap could cause all that grief.