Hi,

 

Cars been running fine until I gave it a drive today, I noticed that the heater wasn't as hot as it should be, car was at normal operating temp according to the dial and the fan would come on and off as normal .but when I parked up with engine off I had a look under the bonnet and saw that the radiator cap was hissing and steam coming from it. Anyone know what this could be? ive spent so much on her the last year im worried that it might be head gasket? ;(

Thermostat stuck, water pump (impeller come off).....

I am guessing it is stuck thermostat so sensors only reading warm......

I'm sure someone with more knowledge will give help soon......

thanks, I hope so

Sometimes the rad cap might not seat properly, crap caught or a failing cap. The cap keeps the system pressurised, the pressure increases the boiling point. So without it not only does the coolant evaporate but it can be thrown down the overflow into the expansion. So once cool check the coolant level, bleed the system out as per the FSM and ensure everything is clean. A new rad cap is a cheap investment. I know the one that came with my japspeed rad was naff and leaked.

 

The second thing is to consider the actual water tempreture, you can either connect an aftermarket or use some software such as conzult to read off the ECU circuit. To give you an accurate reading.you may know this bit but it often catches people out. The stock dash mounted gauge has three stages cold, normal, overheating, so it's not much use tbh.

 

If you find that you do have a sealed system that is being over pressurised then you need to do some more tests. However in my experience in the case of these cars overheating the pressure is more likely to split a pesky old turbo coolant hose or similar than cause. The rad cap to steam. So if the rad cap steams my money is on the rad cap itself.

Thank you, the rad cap did feel loose as in it would wiggle side to side , ill check first thing in the morning, many thanks

Top up coolant level when cold mate, get a head gasket leak test done using hydrocarbon sensitive dye, it may not show a problem when driven gently so be sure to get her on boost assuming she's TT to put gaskets under some pressure.

Sometimes the rad cap might not seat properly, crap caught or a failing cap. The cap keeps the system pressurised, the pressure increases the boiling point. So without it not only does the coolant evaporate but it can be thrown down the overflow into the expansion. So once cool check the coolant level, bleed the system out as per the FSM and ensure everything is clean. A new rad cap is a cheap investment. I know the one that came with my japspeed rad was naff and leaked.

 

The second thing is to consider the actual water tempreture, you can either connect an aftermarket or use some software such as conzult to read off the ECU circuit. To give you an accurate reading.you may know this bit but it often catches people out. The stock dash mounted gauge has three stages cold, normal, overheating, so it's not much use tbh.

 

If you find that you do have a sealed system that is being over pressurised then you need to do some more tests. However in my experience in the case of these cars overheating the pressure is more likely to split a pesky old turbo coolant hose or similar than cause. The rad cap to steam. So if the rad cap steams my money is on the rad cap itself.

 

Thank you, the rad cap did feel loose as in it would wiggle side to side , ill check first thing in the morning, many thanks

 

Considering your first post mentioned a hissing rad cap, with steam coming from it, the rad cap would be my first diagnosis.....

 

I'd start by just replacing the cap - and, considering the age of these cars, do not assume that the radiator filler neck itself is still capable of forming a tight seal. Buy and install a new cap, but do not turn it all the way to the right. Leave it about 5mm short of "fully locked" into place; it is not unknown for the filler neck to wear down at the fully locked position:wink:

 

I had a similar problem a couple of years ago - even after having my waterpump and thermostat etc replaced... And then JeffTT left the rad cap ever-so slightly under-done-up and it's been fine since!

 

Richard:cool:

Hi! I had an over heat problem as a one off!

Turned out to be a radiator cap not seated properly!

Compression test done on water system & no leaks!

Since, no probs!

 

- - - Updated - - -

 

Hi! I had an over heat problem as a one off!

Turned out to be a radiator cap not seated properly!

Compression test done on water system & no leaks!

Since, no probs!

A leaking rad cap has 2 effects...the pressurised water escapes into the expansion tank then because air is drawn in at cool down the system cant create vacume which normaly draws water back up from the tank to top the system back up...so in reality you now have a "total loss" cooling system.

Normally this shows up with the aliens blood effect pouring out by the passenger side intercooler, that's happened to me twice...

Ok ive just removed the cap and there is no visible water even when I squeeze the left hand side radiator pipe. ive checked the expansion bottle and the level is half way up on the dip stick...............

 

Im wondering if this is anything to do with the garage flushing and putting antifreeze in last month. maybe they didn't fill it enough or let any air ect out?

Maybe. I guess it's hard to tell now. Refill and bleed the system as per the FSM and see what happens.

I have a large collection of rad caps as I've had sealing issues with various cars in the past.

I've unscrewed the left hand bleeder screw filled up with engine off until it came out of the bleeder cap took just over 2 litres sarted car left rad cap off and put heaters on full the car is now at normal operation temperature and the stock gauge is just below halfway as always but getting no bubbles at rad area heater is working ok...... But there is an odd noise ill see if I can upload a video

Edited December 28, 201410 yr by leeroy73

Have you jacked the front up in the air?

That looks like condensation from the exhaust mate. . I'm no expert by any means but it looks like it to me..

 

Cutty

Yup, if there was that much coolant getting in, the rad would never stop bubbling as well. Bleed it, new rad cap, bet it's fine.

The fact ur loosing water would be a cause for concern with me & my z!

Have u taken it to a garage & had a pressure test done?

I did this when I had a similar problem next day! Gladly I had no leaks & no pressure loss.

Common head gasket signs, water loss, bubbles in rad, oil in rad water, water in exhaust?

I'm no mech Leeroy73, & not sure on ur noise & cannot speculate.

Hope u get it sorted.