Having f***ed around fitting the glo-dials into my car last week I decided to remove them as they didn't work and the mph were wrong (US). Anyway, since putting them all back together everything looked sweet. My intermittent odometer problem has been fixed in the process but now a new problem has occured. My temp gauge moves to the centre correctly when warming up and appears find but every now and then (not that often), it will go right to the H, stay there for a bit, then come back down the the centre. It has done this during normal driving conditions and I have checked to make sure the engine IS NOT overheating and it appears fine. I get no issues with the engine/power at all or steam etc... I'm still a little concerned just in case it is the engine overheating but I am not loosing any coolant either.

 

Do you guys think I have just upset the temp gauge or is there a way of testing the engine is not overheating without relying on the gauge? Is it worth a trip to the garage?

 

Thanks guys.

 

Dom

Quick check to see if the engine is overheating: If the temp gauge is in the H area, the aircon is off and you can hear the electrical fan behind the frontbumper, then the temp is above 105C/220 F and you're in trouble.

 

If the aircon is on and the elec. fan is on, then the temp is above 90C/195F

It may be irrelevent but temp gauges can display that type of action when you are very low on coolant.

Just drove her round the block a couple of times and the gauge started to rise. It stopped just under the H but I cannot hear fans starting at the front. I turned her off and checked under the bonnet and I can hear the RAD bubbling away so she's obviously overheating. My question is:

 

(i) What is the SUB FAN? I have no relay installed for this.

(ii) As my Air-Con is disconnected I've swapped the relay with the RAD FAN one to see if it's a fault.

(iii) If the car is overheating whilst driving at a constant speed, the engine is not cooling, could it be a problem with the expansion tank?

 

Help needed as I am thinking of getting shot of her 'cos I've had enough!

She's cooled down to just under the half way mark now. I've added 2litres of water into the expansion tank (I haven't done this since I've had it!!!) and left her running for 15mins. Engine temp constant. No problems at all. No white smoke from exhaust amd no bubbling noises or steam from the engine. I have always checked the coolant level from the RAD and it has always stayed constant. Am I right in thinking this is seperate from the coolant tank on the front right of the engine bay and I should also have been checking this regularly? I must add, the dip stick reading does not appear to be reliable!!

 

Advise needed before I decide to sell her!!:cry:

It sounds as though it may have been coolant related, I believe that the needle sits at half way or low because the air passing by it is not as warm as coolant, when a surge of collant goes past the temp sensor sees this as a rapid increase in temperature.

 

have you noticed anything leaking? might be wise to get it to a garage for a checkover if you arnt sure,

You need to fill up the radiator, not the overflow tank.

 

use this procedure:

start engine, put heater on max and fill the radiator until it doesn't take any more coolant.

 

(Note: NEVER use plain water, always use coolant !! )

 

To test if the elec. fan is working at all, you can disconnect the yellow connector on top of the top coolant pipe while the engine is running (watch your hands)....as soon as you disconnect it, the elec. fan should turn on.

 

other signs of overheating: put heater on max and if it starts to blow cold air while the temp gauge is around/above the half way mark, then it's definately overheating.

 

-Eric

See also

 

http://www.300zx.co.uk/forums/showthread.php?s=&threadid=23639&highlight=bleed

 

You gotta bleed the system as well as top it up - especially in your case because if you HAVE got airlocks it might just give you the symptoms you describe!

 

If you look at my sig you'll see why I know aaaaaaaaaaaall about overheating problems...

NAs don't have subfan relay, TTs do.

 

HTH- Gio

I have a twin turbo but have no relay in the subfan slot!!

 

Is that right? What is it exactly?

Boy, that's wierd!

 

Yours is the third TT I have heard of which had a missing sub-fan relay. To quote Ian Fleming "once is happenstance, twice is coincidence, third time is enemy action".

 

Wonder why?

 

The subfan is the electrical one in front of the aircon condenser.

 

(NA condenser fans are off/on, TTs are off/medium/high which is why they need a second relay).

 

HTH - Gio

My aircon is disconnected. Could this be why? Do I need to buy a new relay?

Don't know for certain - I am no techie. But seems logical.

 

Check the pages in the online manual. There is a self-diagnostic for the aircon and it can be tested by Consult / Conzult.

 

If you want the subfan to work you will need a working sub fan relay.

 

HTH - Gio