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Discussion Starter #1
My GT jtdm has just started with an unusual problem. The temp gauge rises from 90 to 100 slowly then drops back to 90 slowly. This only happens at motorway speed 70mph up. It never drops below 90 and is rock solid at 90 when driving around town. At first I thought thermostat but after reading on here it looks unlikely as they usually fail open not letting the car get up to temp. Could be blocked radiator or water pump on the way out, but the most likely after lots of reading on here seems to be a failed first stage of the fan. This would hopefully be preferable and also the cheapest route to a fix. So I need to fix the fan. The second stage definitely works I can hear it kick in but I cannot get the first stage to kick in even standing still and revving the engine once warm.It just stays at 90.
So my question is what do I need to do to test the fan, or change in the way of relays etc.
 

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Discussion Starter #4
It could be something else. it's just that as soon as the fans high speed second stage kicks in the temp starts to drop straight away. When the engine is under load at 70 the temp starts to creep up. If I accelerate at 70 up hill it goes up quicker. Also I read somewhere on this site that the first stage of the fan keeps the temp under control by constantly turning on and off up until around 102 degrees at which point the second high speed stage kicks in.
I would really like to know if anyone knows what to change or check for with the fan as this would be the easiest first step and hopefully cure the problem.
 

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Could be your water pump is on the way out.

I have the 3.2 version which have pumps that have plastic impeller, over time the heating and cooling of the water causes the impeller to crack, when you apply more revs/speed the belt moves faster and the cracked pump doesn't grip the shaft which means the water is getting pumped round the system less effectively.

I'm not 100% sure if the pumps are the same on the JTD but I'm sure I have seen threads about the the JTD pumps being a problem before.

Have a search for water pump threads and see what you can find. It worth checking out though cause water pump failure can damage the cam belt, hope this helps a bit and the fix isn't too expensive.
 

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Discussion Starter #6
I'm not ruling out water pump although it was changed 16,000 miles ago with timing belt.
the more I read the more I'm convinced it's either fan speed resistor, relay or or fuse.
First to check is the fuse. Unfortunately The girlfriend has the car for work today so i can't go and have a look. What is a F06 (MAXI-FUSE). where can I buy one.
Where are the relays located anyone know the part numbers and where I can source one.
Where is the fan speed resistor on the jtdm. Does it come out easily and is there a check to see if it's working. If not where can I get one.

Thanks
 

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Have the same kind of issue with my old 1.9 JTD solid on 90°C when around town or low speed. When on the highway and increasing speed (or driving uphill) upto 120-130 km/h the gauge starts to creep up. One can see when the fan starts to run on first speed and tries to fight back. But if I continue to increase speed or driving uphill it will eventually reach 110°C (and beyond) and starts the fans running on full speed. I noticed that one of the resistors had failed so running only one of the fans at low speed. But replacing the resistor (on the back of the radiator) did not do much for the actual problem. Thermostat and the waterpump has been recently replaced so I guess it's gotta be the radiator that's clogged up even if looks perfectly healthy (all fins fine).
 

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Discussion Starter #8
thanks ardi
I have no indication the fan starts at first speed at all. I just hit a point when the engine is labouring at speed when the temp starts to rise steadily then as soon as the temp hits the 100 or so mark comes back down straight away to 90
 

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how to check the first speed fan, disconnect temp sensor while the engine is running, when you disconnect the sensor the first speed that is slow should kick in, the a few secs after the second speed noticeable high speed
 

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Discussion Starter #10
thanks padraic
where is the temp sensor? If both speeds work is that an indication that both relays and the fan speed resistor are ok?
 

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Seems I will probably have to try to get the radiator replaced. Does anyone have any pointers to how difficult that is on the JTD or earlier posts on the topic.
 

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Discussion Starter #12
My indi seems to think its the water pump also.
I'm having the cambelt and water pump done on Wednesday so ill update if it clears the problem or not then.
I thing the radiator is fairly straight forward you just need to get the front bumper off to get at it. I found an aluminium radiator for just over £80 online ill post aink when I get home tomorrow
 

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tempture sensor is in part of the thermostat housing, if both speeds work on test that mean they are wired up ok to work, first speed resister is ok running at a slower speed. Replacing radiator bumper off is best for JTD, T spark can slip out easy enough without removing bumper. Changed mine a week back and got the scares to show for it 3 hrs. A bit of rust prevention paint wont go a miss while your in the area.
 

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Discussion Starter #15
UPDATE
It was the water pump, spinning freely on its shaft. Paul from aforalfa fitted a new cam belt and pump on Wednesday and showed me the old one which was a cheap version that had only managed 16000 miles before it failed.
Thanks to everyone for your help and especially davidc who in a seperate thread pushed me in the direction of the water pump as the most likely cause.
 

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3.2 V6 Water Pump Plastic Impeller Failure

It has just cost me $4300 AUD to replace my faulty water pump, cam belt, tensioners, radiator, rear brake pads and discs and one CV Boot rubber. This was required on my 2004 Alfa GT. The main issue was the intermittent serious overheating caused by the plastic impeller on the water pump slipping due to a very serious crack in the plastic. See photos! To replace the water pump you have to take off the cam belt and if taking it off it is recommended that it is replaced along with the tensioners and all the gaskets etc. The trouble with the water pump is that it works fine most of the time until you get the engine to rev a bit and then it stops pumping and just seizes up. See the photos. It is a disgrace that Alfa use this part and they should replace at no cost to the owner. I think it is a recall issue. Fortunately you can replace the plastic water pump with a metal impeller type from the 3.0 litre GTV engine. It sure is one costly exercise!
 

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