550 Overheating

My car is a '99 550, purchased from FoW last year. The car runs well and has had no overheating issues until the mercury climbed into the 90's and beyond (just after Easter IIRC .

Josh @ ECS in Virginia did the initial coolant flush & refill and put SRI's silicone hose kit on it (replacing all large AND small vent hoses), and Mark Darragh of Sphere Motorsports here in Houston just finished pulling the radiators and mechanically cleaned and straightened their fins. He also replaced all three coolant sensors under the intake, verified the water pump belt was in good shape (replaced in 2009), and replaced the thermostat for good measure (service records show the 'stat was replaced in 2009 also).

With my NAPA block test kit, I've confirmed there's no combustion gas in the coolant, and Mark pressure tested the system for several hours, so it's not a head gasket issue.

The pix below were taken this last Tuesday or Wednesday, when it was 105 or so, and in stop & go traffic out in The Woodlands. Then yesterday (Friday) I drove home from Mark's shop during afternoon rush hour on 610 and I45, and the temps were similar, if not a bit higher and the Ferrari's thermometer was registering 105/106 outside.

Since I don't have a good frame of reference for the problem, I'd like to know what coolant & oil temps other local, or TX based 550 owners are seeing. Are yours similar?
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Doh.....the 550 has ballast resistors? I sure didn't know that! The sketches and schematics I have don't show any, or I missed them, so I ASSumed they were single speed fans!

Thing is, the problem is occurring both in stop & go traffic, and at speed. But if I really baby it, and keep the rev's below 3000 out on the highway, the coolant temp stays at 190, or just above. But it's a Ferrari for crying out loud - what fun is it to drive around at 2500 RPM?

 

Here's a schematic I posted previously for the 550's fan circuit. Can anyone else confirm if there are ballast resistors in this setup, in order to have two speeds on these fans? If they're there, where are they? I don't see anything but fuses between the +12 and the switching relays, then there's nothing between the relay contacts and the fan motors.

BTW, that last white mark before the red zone is 234 degrees F / 112 degrees C. I had my OBDII scanner & software on the car this morning and measured the coolant temp with that.

As a confirmation of the gauge's accuracy, the OBDII software indicated 190 on the dot when the gauge needle was on the 190 line.
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Yep, I've got a related thread going in that section called "Ron Davis Radiator for 550?" or some such. I think that'll be my final destination on this journey.

Hehe, yea I had an old E type and learned several of those tricks. I'm just not willing to do all that with a car like this, and want to get it sorted "properly" (perhaps famous last words.....)

 

Thanks Josh, I'm going to try to get some current measurements on the fans today to see if they're "aging" like the 355 owners have been experiencing. The 550 and 355 use the same SPAL fan (SPAL type VA18-AP6-42A, P/N: 30102113), with the open type motors that let all the crud in. They're SPAL's highest performing 16" fans, but are also known to fail sooner, as you pointed out. What's interesting to me is that if the 355 guys are having cooling issues with their 3.5 liter V8's as these fans age, then these fans must REALLY be marginal trying to cool a 5.5 liter V12. Granted the ducting and airflow on the 550 is probably better than on the midengine 355, but still.......

I know the temps will climb to the last white line (234 degrees F) and possibly higher - I had the car idling in my garage yesterday, and they climbed up to that line while I was monitoring with my OBDII stuff. When they hit that point, I chickened out, and turned the A/C off and opened the hood to let it cool down a bit.

Radiator is already a two pass design (both inlet & outlet hoses are on top) so can't easily make it a three pass. Four pass would be the only other "possible" configuration, but IMO not practical.

512Blu, yes I have an IR gun and am going to take some temps at the radiator inlet/outlet today, and will give you a ring later, thx.

Tex, currently the car has a 50/50 mix of glycol coolant & water. No Water Wetter or Royal Purple this time (yet).

 

I didn't get current measurements of the fans yesterday, but will try today.

I did shoot the radiator in/out connections with my IR gun last evening after wifey & I had gone for a cruise. This was in my garage, where the "ambient" was still probably around 100 degrees @ 9PM:

Radiator Inlet: 225F
Radiator Outlet: 218F

This, to me, indicates it's a fan problem, because the deltaT across the radiator isn't that great, and the outlet temperature is too high. The heat being dumped into the radiator by the engine simply simply isn't being transferred fast enough to the atmosphere by the fans.

If it were a coolant flow (pump) problem, I think I'd still have a high inlet temperature, but a good deltaT across the radiator.

Any heat transfer / thermo specialists here disagree?

I think it's probably time to get a new set of fans coming, and I'll start working on a new radiator/fan setup for next year

 

No kidding, but what we (and at the moment, me especially) do need in Texas in August is the boilover protection that the ethylene glycol provides. Just running the system with a bit of pressure in it isn't enough when the temp gauge is hitting 234, and then when you shut it off, and lose what little pressure protection there is, well it's probably sure to boilover if it's basically just water in there.

I'll give it a look; I've always used Redline Water Wetter in the past, but I understand the Royal Purple stuff does the job, too.

Agreed, and I'd really like to cut the amount of glycol right down to the bare minimum needed for freeze protection and run mainly distilled H2O & Water Wetter also, but with my temps running as high as they are currently, I can't chance it.

 

Here are some current measurements I took from the fans this morning:

...............Starting Amps............Running Amps
Left Fan.........49.............................15

Right Fan........51.............................15

I had already decided to bite the bullet for a new set of fans (SPAL model 30102113, same as the OEM's), so I unpacked one, and measured its current (this is running in free air):

New Fan.........57............................18-19

All these current measurements were surprisingly low, considering SPAL rate these fans close to 25-26 amps in free air, so I picked up a 2nd ammeter this morning, and confirmed the readings were correct (or if not correct, at least my two different ammeters agree).

So, not a huge difference in current between the old fans and new ones, but perhaps the old ones are a bit weak...... Still, I'd expect their current readings to be higher, due to higher inefficiency from age, crud buildup in the open motors, etc. I'm going to go ahead and install these new fans, however I'm not optimistic that they'll be the final solution....

I also measured the core of the radiator and was surprised how small it was; only 24.25" x 19.125" x 1.25" thick. This is only 464 in2 of frontal area, which to me, is undersized for a 475 HP engine (464 / 475 = 0.97 in2/HP). I'm accustomed to having "at least" 1.25 in2 of radiator core per HP. Granted the oil cooler core adds another 143 in2, so that helps, but on the coolant side, the radiator definitely seems undersized, at least for our Houston climate. So it's no wonder Ferrari put 2 of SPAL's highest output fans on it.

For sake of comparison, my other hotrod, a Toyota Supra, had a stock radiator with a core area of 457in2, plus an oil cooler of 120in2. And this was for a 3.0 liter turbocharged engine rated 320 HP. That's 457/320 or 1.42 in2/HP, or a 46% larger radiator core per HP of engine output......

So as Jim mentioned below, the car's cooling system probably isn't well suited for hot climates and stop & go traffic. It "needs" to be out on the autobahn/autostrada doing 80-100 MPH in 75-80 degree ambient temps, not stuck in Houston bumper to bumper, stop & go traffic when it's 106 degrees.

 

Thanks for that data. The obvious question then is, what's different between your 550 and mine?

Have you had your fans replaced, the water pump rebuilt, or a new radiator mounted? Or had the radiator cleaned "aggressively"?

Those are about the only things left that I haven't done, and the new fans are going on tomorrow.

And out of curiousity, what's your engine build number? Is it higher than 53756? Apparently Ferrari revised the water pump for engines later than that.