Overheating 75's & 90's-how common is this ?

[MD]

Previously had a 90 and now have a 2.5L 75 both of which develop overheating issues in traffic.

The integrity of the system is good, new coolants with 50% ethyglycol mix, thermos ok,clean core and fins, thermo fan kicks in just right on cue and works well. Timing is right. Fuel mix is not lean.

I have gone to the trouble of installing a "push" (condesor) fan in front to supplement the  draw fan in the engine bay but with only marginal benefit.

When the cars run on the open road, there's is never a problem no matter how much of a flogging they get. In traffic it is a different story.

How common a problem is this out there? Is it an undersized radiator for Oz or have I missed something?

[Sheldon McIntosh]

Mine usually get up to 100 in traffic, thermo fans come on and bring it down to 80.  Depending on weather will run 60-70 on the open road, and just over 80 on the track.

[MD]

So not such a common problem being reported out there eh?

[dehne]

my road 90 usually sits on 80 but in heavy traffic can get up to 100+ as like sheldon i would not worry to much this is a factory issue

[Southern75]

I never have any problems in the traffic with mine but it does get to about 100-105

The 75 and 90 do have a smaller radiator than the gtv6 but the extra cooling is granted by having such a large electric thermo fan.

You can fit a davies craig thermo fan which will more more air but will set you back around $300.

You can also get a PWR radiator for the 75 (believe it or not it is a stocked item) which offer a more efficient setup but these are big money and i opted not to go down this path and went for a new standard one instead.

Honestly ... i suspect there is something wrong with your water pump or the system is not correctly pressurised.

[MD]

I found out what the culprit is. It simply is manufactuirng/engineering spec. for this radiator type that simply is doomed to perform that way mine does. The reason is that the cross section of the almost round tubes is too large and the number of fins per inch is too fine. With the fins being so close together, a combination of engine compartment oil fume and road dust causes the fins to become semi blocked and therefore minimal air is actually flowing through them unless at speed on the open road. So a combination of low air flow and limited tubes over the radiator area produces marginal heat scrubbing. Radiators with a much more sparse number of fins still give good heat exchange but are able to pass this "debris" through and not hang onto it to limit air flow.

We took one of the side tanks off just to be sure there are no blockages in the pipes and it was as clean as a whistle which indicates good coolant management through the life of its 22years on the road. Got to be greatful for something!

The solution is that I am installing a typical "flat" tube three row 13 FPI core and new brass tanks $330.00 custom made. Reinstalling the thermo switch and original fan with a modified shroud to reduce suction blow by.

I'll let you know what temps we run after that.

By the way the rubber seals around the tank/tubes were just starting to crack indicating a future failure. Anyone owning a vehicle of this age should have the radiator assessed to avoid steam clouds under the bonnet at the most inapproriate time as per norm !

[MD]

So finally the day of reckoning has come. Installed the new radiator and hooked up the electrics. Filled with mixture of distilled water and ethyglycol brew. Bled the system and checked for any leaks. No worries there. Ran motor up to temp slowly and waited for the fans to kick-in. Right on cue they chimmed in and immediately started to drop the temp. That's not happened so readily before-first sign.

Second sign is that operating temp now oscillates between 82* and 88* which is perfect. Gave it a flogging within an inch of its life and still rock steady. Awesome.

In traffic the same deal. End of high temps.

So the proof in the pudding is LESS fins per inch and MORE tubes.

In the photos. Note the fins per inch comparison between new and old. Also note how large in comparison the diameters of the 75 tubes and how few there are compared to the new radiator that has a larger number of tubes that are thin and flat. THAT'S WHY IT WORKS.


Icing on the cake is a third row for good measure and all rows are staggered.

[Darryl]

Nice. Where from?

[MD]

Valley Radiators. The core is from a Hi-Lux. Please ad GST to the price quoted (as I found out) but that's $300 cheaper than two other quotes I had.

[alfagtv152]

And there endeth the lesson.Thankyou and Good stuff Mickey!.
Cheers
Andrew

[MD]

No it doesn't.

Now I am chasing an ignition gremlin....

Ah, Alfas !! You gotta love 'em. They keep you challenged don't they ?

To maintain pressure on their competitors, I am sure Japanese car manufacturers hire Voodoo Queens that carry Alfa car dolls and every now and then they pull or blow a fuse here and there just enough to to piss the owner off.. Gotta be, there is no other rational explanation..