ZD30 running warm....

[GUIV]

Ok the story goes like that... *In the last trip, while travelling down south on Forrest Hwy (travelling 110-120 kph), the temp gauge went to maximum. *I pull up straight away and the temp went down. *I continued the trip in harvey without any further problems. *

The next day I replaced the thermostat and coolant. *The old thermostat was working fine. *However, the coolant was very pale green, due to it being dilute too many times (I had a hole on the heater hose).

Anyway after this, the car runs normal again, until the other day, on Freeway with 7 people on board and traveling at 110 kph, the temp creep to 3/4. *It never used to do that. *When the speed drop slightly (about 100-105 kph), the temp will drop back to about half in about 20-30 min.

Normal driving does not seems to have any problem as long as speed remains below 110 kph.

I need to solve this and have the following questions:

1. *How do you know if the water pump is working fine? *If at running temperature and the water seem flowing if you remove the radiator cap, does it mean it is working?

2. *How do you know the viscous fan hub is working? *It is still spinable when the engine stop (you can feel a bit of resistance). *you can feel some "wind" when running at fast idle (about 1500 rpm). *Is that good enough?

3. *If it is not the water pump or the fan, then the radiator may be block internally. *Anyone know any good place to get it "rodded (it is the correct term for cleaning the rad internally)"?

4. *What other possible cause(s)?

Thanks guys....

[Bigrig]

Ok the story goes like that... *In the last trip, while travelling down south on Forrest Hwy (travelling 110-120 kph), the temp gauge went to maximum. *I pull up straight away and the temp went down. *I continued the trip in harvey without any further problems. *

The next day I replaced the thermostat and coolant. *The old thermostat was working fine. *However, the coolant was very pale green, due to it being dilute too many times (I had a hole on the heater hose).

Anyway after this, the car runs normal again, until the other day, on Freeway with 7 people on board and traveling at 110 kph, the temp creep to 3/4. *It never used to do that. *When the speed drop slightly (about 100-105 kph), the temp will drop back to about half in about 20-30 min.

Normal driving does not seems to have any problem as long as speed remains below 110 kph.

I need to solve this and have the following questions:

1. *How do you know if the water pump is working fine? *If at running temperature and the water seem flowing if you remove the radiator cap, does it mean it is working?

2. *How do you know the viscous fan hub is working? *It is still spinable when the engine stop (you can feel a bit of resistance). *you can feel some "wind" when running at fast idle (about 1500 rpm). *Is that good enough?

3. *If it is not the water pump or the fan, then the radiator may be block internally. *Anyone know any good place to get it "rodded (it is the correct term for cleaning the rad internally)"?

4. *What other possible cause(s)?

Thanks guys....

No doubt people will be able to assist with this one mate, but any specialist radiator joint should be able to give the radiator the once over and do a proper flush of the cooling system which sounds likely to be the problem ... the thermostat potential has been removed by replacing it, and the water pump could be checked out when doing the radiator, but there are ways to check it that others will be able to assist with (YNOT on here did the same thing with mine!!).
Good luck with it champion!!

[YNOT]

1. *How do you know if the water pump is working fine? *If at running temperature and the water seem flowing if you remove the radiator cap, does it mean it is working? If you can see coolant flowing in the radiator at operating temp that's a good sign that the thermostat is opening and the water pump is working. If your water pump was not working you would not get more than a few kilometers without it boiling.

2. *How do you know the viscous fan hub is working? *It is still spinable when the engine stop (you can feel a bit of resistance). *you can feel some "wind" when running at fast idle (about 1500 rpm). *Is that good enough? When the engine is cold and you spin the fan by hand it should spin about half a turn before stopping. With the engine running and at operating temperature and the bonnet up run the engine at about 1500rpm for about 5 minutes, you should be able to hear the fan "cut in" and start to roar at times as the viscous coupling detects high heat. Usually after a minute or 2 of cutting in you will hear it cut out again, it will still appear to be spinning at the same speed but it won't be roaring.

3. *If it is not the water pump or the fan, then the radiator may be block internally. *Anyone know any good place to get it "rodded (it is the correct term for cleaning the rad internally)"? This seems the most likely cause to me. If the radiator has a partial blockage it will not have enough headroom to cope with higher than normal heat loads.4.

*What other possible cause(s)?

Tony