V6 overheating - causes? - Alfa Romeo Forum
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(Post Link) post #1 of 7 Old 12-07-10 Thread Starter
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V6 overheating - causes?

My V6 sits at a perfect 90 when driving along, but in this hot weather the gauge has been soaring up to 115+ quite quickly when sitting in traffic through town. It settles down again after moving along for a minute or two but is still a little alarming! The radiator and thermostat were done 18 months ago, I can hear the fan come on and all its blades are intact, and the coolant header tank is full. What else could be causing this? All I can think of is the water pump but that doesn't really make any sense to me...

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Was the water pump ever upgraded to one with a metal impeller?
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(Post Link) post #3 of 7 Old 12-07-10 Thread Starter
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The waterpump was changed (under the previous owner) with the cambelt 4 years ago - due for a change again any time now actually. The part no. on the invoice is 0055198357A Water Pump (2.5 24v) - perhaps someone can check that for me but as it states it's for the 2.5 I assume it's the plastic one, the metal one was for the 3.0 wasn't it?
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You should probably do a waterpump change at some point soon as it appears you have a plastic one fitted, but getting hot at idle isn't typical of a slipping waterpump. Normally they grip at low engine speeds when they aren't moving a huge mass of coolant, and when placed under load they slip.

Perhaps you have a bit of an air-lock, or your coolant cap isn't holding pressure allowing the coolant to boil? Its supposed to be a self-bleeding system but if your radiator has a bleed nipple it can't hurt to open it with the engine running and see if any air comes out first before the water does. Watch you don't burn yourself though.

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(Post Link) post #5 of 7 Old 12-07-10 Thread Starter
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Would an airlock cause this, I'd have thought it would manifest itself with the temperature gauge being a bit erratic, jumping from 90 to say 115 and back quickly every few seconds? I do need to get the cambelt done so will have the pump changed at the same time, be silly not to really...

I'll have to have a look at the rad etc some time, too. Is it possible that an incorrect ratio of coolant-to-water could be another explanation?
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My car did the same thing i wipped out the fan resistor which was broken at a point of contact, i repaired it and the temperature gauge goes up to 90 and holds there now with the fan running which it was not doing before, Best thing is to run your car up from cold then make sure the fan is cutting in properly and as Pud says check and bleed the system if needed too, i am doing my cambelt in about a weeks time on my v6 while i do it i am flushing the system through & changing water pump and thermostat too while everything is open.
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Maybe you have asticking thermostat. You say it is quite new but I wouldn't rule it out.

You may have an airlock, try removing the expansion tank cap when the engine is cold then letting the engine warm up until the fan kicks in that was bubbles should rise to the top.

(or try opening the bleed scred on the Rad as Pud suggested)

The only trouble with opening the bleed screw is that is if the water in the rad is over 100C it will come out as steam, which will make you think that air is coming out.

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