Overheating (according to gauge) minutes after starting - KV6
 

I am trying to diagnose the issues my 2002 ZT V6 has.

The temperature gauge goes above half way when the engine has been running for just a few minutes.

There is hot air from heaters.
Coolant and oil look good.

If the engine is started with the expansion tank cap off, the coolant level rises almost immediately and will overflow.

I have tried bleeding air out. With the engine off, coolant flows nicely out of the bleed screw hole. When the engine is started, coolant pretty much stops flowing out of the bleed screw hole (but level in tank will rise).

What are peoples thoughts?

Have you run the on board temperature diagnostic to see what temp you are actually reaching - surely if too high your fan should kick in to bring the temp down?

Not a V6 man but so many times this kind of issue on the V6 is down to incorrect coolant filling procedure or failing thermostat/coolant hoses.

How to access the cars diagnostics below - this will give you the actual head temp -the gauge is unreliable - can be anything between 75 and 115 c once you pass 8.54 on the gauge..

https://the75andztclub.co.uk/forum/s...ad.php?t=60365

You've definitely got an air lock, so a proper bleed is required.
You need to do it by the official MGR bleeding proceedure, which is given in RAVE and the Haynes Manual:

1. Remove the bleed screw in the hose located between the engine and air filter.
2. Detach the (narrow) hose from the side of the header tank filler neck.
3. Remove the bolt securing the header tank to the radiator top and swing the tank backwards so you can unhook the side mounting pegs.
4. Lift the header tank as high as it will go (about 5 inches), ensuring none of the plastic hoses are kinked.
5.Slowly fill the cooling system, keeping the header tank full to just under the neck, until coolant emerges from the bleed hole as a steady stream.
6. Replace and tighten the bleed screw.
7. With tank still raised, continue filling the system until coolant level settles just below the filler neck.
8. Lower the header tank and refit it usng the locating pegs and mounting bolt.
9. Refit the narrow hose back onto the tank neck connector.
10. Leave the pressure cap off.
11. Ensure the aircon system is off.
12. Start the engine and have an assistant run it at 1500-2500rpm.
13. Be prepared to top up the header tank as the engine starts and maintain the level just below the filler nek.
14. When the coolant level starts to rise due to heat expansion, refit and tighten the pressure cap.
15. Maintain a fast idle until the cooling system gets hot and the radiator cooling fan trips on.
16. Allow the fan to reduce the temperature until it switches off, then stop the engine.
17. Allow the engine to cool completely, preferably overnight.
18. Check the work area for leaks.
19. Check the coolant level and adjust it to the MAX marker.

Avoid adding your own steps or wavering from the official method.

TC

I went out to it again and ran the diagnostic test through the dash so I could read the temperature. Temp read approx 23, started it up (with cap off) and within 20 seconds coolant raised right to the top of the tank,. Put cap back on and went for a drive. By the time it was reading approx 55 the gauge was over half way.

The rad fan is not working. It doesn't come on when set to windscreen or econ off, nor when I disconected the trinary switch and bridged it

I know the 4 cylinder k series can be a pain to bleed, especially if the giggle valve is blocked or stuck, but I never thought kv6 was too? Never had a problem bleeding my dads ZS180 when I done a coolant change

The KV6 engine is the most tricky of them all when it comes to the coolant filling process - so many folk get airlocks when the official procedure is not followed.

Correction
 

This is an error made by and copied from Haynes. No hoses should be detached from the expansion tank.

What RAVE actually says is this:

"Release expansion tank bleed hose from clip on top hose."

This is simply so that the narrow bore bleed hose does not restrict movement of the expansion tank when it is raised.

Simon

Hi Ashley,

This is very odd. The temperature gauge and instrument pack diagnostics are fed by the same coolant temperature sensor. :confused:
How long have you owned this car?
This is not going to help diagnosis. In fact, it's going to make overheating likely. You should repair this before going any further. Do you have a 2 speed fan with a resistor or the 3 speed type?

Simon