Alfa 75 2.0 TS cooling problem after new radiator fitted! - Alfa Romeo Forum
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Alfa 75 2.0 TS cooling problem after new radiator fitted!

Hi all,

I recently fitted a brand new radiator to my 75 (the old one was leaking). Even with a faulty radiator, the car always cooled properly. Ie, if sat in traffic, the temp gauge would go up to 90 degrees, the fan would cut in for a minute and the temp would drop to 80 degrees again. It would sit and do that all day and has operated this way for the 16 years I've owned the car until fitting a new radiator!

Since fitting a new radiator, I noticed that the fan comes on for much shorter bursts/intervals when it reaches temperature. I got stuck in traffic last weekend and the gauge just kept on creeping up even though the fan operated in short bursts. Basically, it doesn't appear to be doing the job properly. Luckily, I was able to get out of the traffic jam and the cool air soon brought the temperature back down to 80 degrees.

I'm not sure what could be causing this. There are no air locks/problems in the system. I wonder if the fan switch doesn't like the new radiator and whether this could be the issue. The thermostat seems to be doing its job properly otherwise it wouldn't get up to temperature.

If the fan switch is a problem, is there a particular make I should look at buying or do I go with one off Ebay?

In true Alfa style, you fix one thing and something else immediately goes wrong!

Thanks in advance for any suggestions!

Rockin' all over the road!
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How do you know there are no air locks? Can be very hard to eliminate. Also, maybe water pump, or even a wire knocked loose when replacing rad?

I feel your pain though!
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Originally Posted by gralegav View Post
How do you know there are no air locks? Can be very hard to eliminate. Also, maybe water pump, or even a wire knocked loose when replacing rad?

I feel your pain though!
Could double-check for air locks I guess. Water pump is fairly new - only about a year old!

I'm also fairly sure I fitted a new fan switch too. Not sure what we'd need to do to check for an air lock. Seems highly unlikely as it comes up to temperature perfectly fine. The cooling fan doesn't appear to kick in for long enough - not like it used to. It could be faulty fan switch that I fitted I guess.

It's not major as I rarely get stuck in traffic with the car. It only goes out in the dry and for fun! I do need to sort it out though.

Perhaps I'll just get another fan switch and try that. They're not expensive and I can collect all the coolant in a bowl to save having to replace it all! Depends how quickly I can unscrew / screw in the new one. Again, I'm fairly confident no wiring got disturbed. Removal of the radiator is a very easy job and there's loads of room to work. I cleaned everything up prior to refitting too. It's a mystery but I keep coming back to the fan switch....
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Just a guess, I don't know if you already checked this:
it is possible new and old switch have different temperature set points.
If I remember right, on every switch you have T1 and T2 (T1<T2):
- at T> T2 it closes the electric contact (start fan)
- at T< T1 in opens the electric contact (stop fan)

If T1 is too much near T2 (or equal), you got frequent and shorter bursts.
Possibly old swith had T1 lower than the new switch,
so longer burst and lower average engine temperatures.

Even selecting spares for one specific car, it is possible different
switch brands have different "nominal" or "real" T1 and T2,
you can try to verify, T1 and T2 can be impressed
on the metal part of the switch (not sure if general rule)
or on the packaging they where in??

Ps.: on the other side, if new switch can be a bit too much on
high temperatures, not sure if also the old switch was a correct one,
80 degree it seams a bit too much on low temperatures?

But also car temperature instrument could be wrong few degrees.

Last edited by bobkelso; 20-10-16 at 18:59.
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Quote:
Originally Posted by bobkelso View Post
Just a guess, I don't know if you already checked this:
it is possible new and old switch have different temperature set points.
If I remember right, on every switch you have T1 and T2 (T1<T2):
- at T> T2 it closes the electric contact (start fan)
- at T< T1 in opens the electric contact (stop fan)

If T1 is too much near T2 (or equal), you got frequent and shorter bursts.
Possibly old swith had T1 lower than the new switch,
so longer burst and lower average engine temperatures.

Even selecting spares for one specific car, it is possible different
switch brands have different "nominal" or "real" T1 and T2,
you can try to verify, T1 and T2 can be impressed
on the metal part of the switch (not sure if general rule)
or on the packaging they where in??

Ps.: on the other side, if new switch can be a bit too much on
high temperatures, not sure if also the old switch was a correct one,
80 degree it seams a bit too much on low temperatures?

But also car temperature instrument could be wrong few degrees.
Some interesting points there. The fan definitely works in shorter bursts. It used to cut in just over 90 degrees and bring it down to a steady 80. It's always been like this for the last 16 years! I just got nervous when stuck in traffic as the cooling fan didn't seem to have much of an effect. It was cutting in but the gauge gradually climbed up to just over 100 degrees which defo isn't right so I was fortunate enough to escape the traffic jam and get the temperature back to normal. I may check with Alfashop re the 'T' settings on their switches. The one I replaced it with came from Ebay so that can sometimes be no good thing!
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One other thought, did the rad come with a new fan attached? I've seen them fitted and/or wired the wrong way round, so the fan then makes the car run hotter!
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Originally Posted by gralegav View Post
One other thought, did the rad come with a new fan attached? I've seen them fitted and/or wired the wrong way round, so the fan then makes the car run hotter!
No, it still has the original fan and wiring all intact. I think the fan switch is at fault here. Will need to see if I can get one with lower cut-in temperatures as mentioned above.
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