[cribbj]

My 550, which prior to me buying it, spent all its life in & around VA, isn't coping well with its first Houston summer. I can sympathise as I nearly packed up and went home about this time 36 years ago after the mercury topped 100 for two weeks straight, and the humidity made it unbearable to be outside.

The 550 is overheating at idle & in traffic, but once up to speed, it seems to cool down.

The car has had a coolant flush & fill in the last six months, and is running a 50/50 mix of red ethylene glycol & demineralised water, with a bottle of Water Wetter added for good measure. All coolant hoses except the top two for the radiator in/out have been changed/upgraded to SRI's silicone hoses and the system has been burped & bled several times with heater running full blast and front end elevated. I've checked the coolant for the presence of combustion gas with a block tester, and that's good so the problem isn't a BHG, thankfully.

Next step is to bring it to Sphere Motorsports and get the radiator & A/C condenser pulled and make sure there's no fin blockage (A/C ran fine during winter & spring then decided to pack it in with the onset of summer. How convenient .)

Then I'll get a steam vent line installed between the radiator/thermostat and expansion tank. I may get a new thermostat put in at the same time.

After that, it's pulling the intake plenum and replacing the coolant sensors on the L&R coolant manifolds as the fans might be coming on too late.

If all else fails, then it's a new set of fans and possibly a new Ron Davis radiator. Apparently our 550's use the same fans as the 355's, and these are known to lose efficiency and/or fail completely with age, due to their nonsealed motor construction. The 355's being generally older cars than the 550's have been experiencing this problem for a few years, so it will be something for 550/575 owners to watch for in the future.

Here's a pic of my coolant temp gauge taken in traffic the other day when the ambient temp was only 95. Since then the outside temp has been as high as 105/106, so I haven't even attempted to drive the car. Would anyone know what temperature that last white mark is before the 260? If it's a linear scale, I'd expect it to be 240 or maybe 250, but perhaps this is one of those expanded scale gauges, where the low & high ends are logarithmic, and the middle is linear (at least that's what I'm hoping )

The oil stayed on 210, so I'm thinking it's not the fans coming on late, and may well be the thermostat sticking.

[t1fosI]

Originally Posted by cribbj

The 550 is overheating at idle & in traffic, but once up to speed, it seems to cool down.

Another consideration is the waterpump. Assuming you are not losing coolant and no significant pressure build up.

re a/c - assuming that you have good system pressure (i.e no discernible leaks), refrigerant is full strength and the compressor is not seized. Another thing to perhaps check would be the secondary fan (a/c fan). If this is inoperative for some reason, e.g damaged wiring, it can affect the a/c compressor operation and the cooling.


.

[cribbj]

Thanks for the suggestions. You might be on to something with the water pump; I noticed that if I revved the car just a bit higher than normal idle, the temps came down. I understand that others in hot climates have had undersize water pump pulleys fabricated for their 550's and this has helped the cooling.

Re: the condenser fan - I'm not aware that the 550 is equipped with one? It's not shown in the parts diagrams, although most modern cars do have a secondary pusher fan out in front of the condenser, and I thought it odd that this car doesn't? That means the condenser really has to work to reject the heat in the R134 when the car isn't moving, and the main fans aren't running.

I'm probably going to eventually install a set of variable speed fan controllers on this car, and I'll set them to have the fans working at least 50% speed whenever the A/C clutch is engaged. Fan motors, like any other motors, do not like to be started and stopped frequently. It's far better for them to start when required, then leave them running but vary the speed according to the demand. This is the approach currently being taken by most of the OEM's and it performs better, the fans last longer, and it should be quieter as well.

[t1fosI]

Originally Posted by cribbj

I'm probably going to eventually install a set of variable speed fan controllers on this car, and I'll set them to have the fans working at least 50% speed whenever the A/C clutch is engaged. Fan motors, like any other motors, do not like to be started and stopped frequently. It's far better for them to start when required, then leave them running but vary the speed according to the demand. This is the approach currently being taken by most of the OEM's and it performs better, the fans last longer, and it should be quieter as well.

You are quite right there does not appear to be a specific condenser fan. is it possible that one of the main fans is linked to the a/c system? The controllers are a good idea.


.

[cribbj]

Car has now been through Sphere Motorsports where the following was done:

1. Coolant & oil radiators were removed, and cores were "combed" and cleaned externally, and some fins straightened. Apparently a good deal of crud was trapped in there and was removed.

2. Inlet manifold removed and all three coolant sensors replaced (1 for the gauge itself and 2 for the radiator fans on/off control). All inlet gaskets replaced as well.

3. All hoses under manifold confirmed to be in good shape (all are SRI silicone, and were replaced in December)

4. Water pump belt confirmed to be in good shape (changed in 2009)

5. New coolant 'stat installed (also changed previously in 2009)

6. Top two radiator hoses replaced with SRI silicone hoses

7. Block was pressure tested and no leaking down, so head gaskets are tight. I'd already tested for combustion gas in my coolant, so I was fairly confident the problem wasn't head gaskets.

8. Fresh fill of 50/50 coolant

Result: Car doesn't overheat quite as fast, but still will if revs are over 3000 - 3500, and/or I'm inching along in traffic, or it's sat idling in a semi-closed area (garage) with the A/C on.

If I'm out on the highway, and there's tons of air moving through the cores, AND I keep the revs below 3000 or so, it won't overheat. Woohoo, what fun, toodling along in your Ferrari at 2500 RPM.......

BTW, I discovered what that last white mark before the 260 degrees indicates - it's 234 degrees F (112 degrees C). Hooked up my OBDII scanner & PC software and measured it this morning. Pretty toasty!

Ambient conditions: 105 degrees F

Next on the checklist, installing a vent line from the block to the expansion tank.

Then trying a slightly smaller water pump pulley. I discovered the pulley for the 456 & 575 is 93mm vs mine, which I believe is somewhat larger than 100mm (I've heard both 106 and 110).

Then it's either a new set of fans and/or a new radiator.

The A/C problem was low freon due to a leaking Schrader valve on the high pressure line.

[Granucci]

Several items to consider as it were in my case too:
- Heater core should be considered suspect. IF used, it may help with more blockage to what you already cleaned.

try when it gets hot, to use the heater on and see what goes.

When mine was overheating, we had to use the heater on a hot day to bring the temp down as the ambient temp does make quite a difference BUT, ONLY if I were using the car a higher revs and then coming to a slow, non-air flow moment. The fans seemed to work fine on the NEW radiator and heater core, but can look identical to what your pics shows, and I as you, run the same mix with water wetter to the tune of an entire bottle per mix--which is ok according to the factory!!

Matter of fact, When Brian Crall remfgr'd a new radiator, he increased the interlacing of the tubes between it and the oil radiator just a few extra inches to make it even larger. Can't remember the percentage, and the Oil rad didn't seem to make the water tubes more a problem, but it DID bring the temps down...for a bit. as the ambient temps are the key here and the speed in which you travel.

I'm quite certain you haven't as much problem at higher speeds.

I as you wanted to increase the air flow, but thought more about the bottom end allowing more draft: Perhaps something to explore a bit later. My temps are tolerable and the engine is running fine, and I just passed the 71K mile mark last weekend.

These engines run hot, and need the air flow. period. I would be tempted for a better fan too. Do you find your fans work ok, like when sitting idle etc.?

oil, and I'm sure you do that area fine, is of course a concern.

[cribbj]

Rik, thanks for your thoughts; when it's overheating, I'll turn on the heater and watch what happens to the temps.

I burped the system the other day while the car was on my driveway incline, and that was with the heater running full bore, and it seemed to not get quite so hot with the heater running. So I think the heater is probably doing a fine job as an auxiliary radiator (BTW burping did no good whatsoever - no steam or air came out, only coolant)

What I'll probably end up doing is driving the car to Phoenix and tell Ron Davis Radiators to put the biggest d*mn core they can fit in my engine bay, plus I have some pretty radical ideas for new cooling fans that I'll try if it comes to that.

[Granucci]

Like to hear your ideas on the fans. IF requiring larger current, and/or other changes to thermo settings, it would be interesting to understand those changes.

Will have to look, but perhaps kicking in the fans on a diff. setting might do the trick.

[viabono]

You are running pure "distilled" water through your system, correct? Not tap or filtered water.

[viabono]

I reread your initial post and see you are using demineralised water. I went through a similar overheating problem years ago when an old mechanic told my father to start with "distilled" water and absolutely nothing else. I don't know if demineralised is the same as distilled water, but he was specific that it had to be distilled water. We were highly skeptical, but we had gone through everything you have done twice and had just given up on the car. Everything had been working perfectly so this was a simple low cost attempt with no downside and even less expectation of success before giving up and selling it. Well, it worked! There is a painfully simple reason it worked, but I'm not a mechanic nor a chemist to explain it. It may be worth a try given it's a hell of a lot cheaper than the alternatives and may be part of the solution if everything else has already been confirmed to be working as designed.

[cribbj]

Originally Posted by viabono

You are running pure "distilled" water through your system, correct? Not tap or filtered water.

Demin is basically the same as distilled, but is made without distillation. It's softened then is run through an RO system. It has all the good qualities of distilled water.

The way I see it, one of the following is the culprit:

1) Trapped air/steam in the system (I'm about to install a steam vent line to eliminate this possibility)

2) Water pump isn't moving enough coolant through the engine fast enough to pick up the heat rejected. (To confirm this, I think I should have good deltaT across the radiator, but an abnormally high inlet temp)

3) Fans aren't rejecting heat from the radiator to the atmosphere fast enough. (To confirm this, I think I should have a low deltaT across the radiator and an abnormally high outlet temp)

I have a IR thermometer gun I'll use to shoot the inlet/outlet of the radiator to see if either 2 or 3 are the problem.

[cribbj]

Originally Posted by Granucci

Like to hear your ideas on the fans. IF requiring larger current, and/or other changes to thermo settings, it would be interesting to understand those changes.

Will have to look, but perhaps kicking in the fans on a diff. setting might do the trick.

Rik, If it comes down to a new radiator, I'm going to increase the core size as much as possible, within the confines of the 550's engine bay. It'll definitely be larger in frontal area and probably thicker too, but not at the expense of having to cut or modify the sheet metal ducting/shrouding around it. And as you mentioned, there's wasted area between the oil & water radiators that could be put to much better use. In another life when I was designing & building large gas compressors, our cooler suppliers would build finfan coolers with oil & water sections that fit together much cleaner than this setup, and I'm thinking to borrow a few ideas from those.

On the fans, I'll want to set them up so that their coverage of the core is much greater than the way Ferrari did it. Here's an interesting photo from the rear showing how the OEM fan setup covers the two cores:



Pretty dismal isn't it? I'm guessing there's from 15-18% of the core that has no shroud coverage, which means no air is being drawn through that section except at higher road speeds. Some will say that fan coverage is only relevant at idle and low speeds, and they could be right, but IMO, the best working fan setups will maximise the fan blade footprint to the radiator core area. There's better ways to do this than with two big fans.

Too, the OEM shroud is so shallow that it really doesn't help the fans to pull air through the entire shrouded area. So I suspect that hourglass shaped shroud section between the two fans is actually an area of dead, or nearly dead air space, same as the triangles in the four corners, so IMO the fans are effectively only pulling air through the core from an area the size of their own "footprints". Since we're limited in depth and can't put an optimised deep, tapered shroud in there, I would look instead to maximising the fan footprints to the radiator core, and perhaps eliminating the shrouding altogether as it's really too shallow to be of any use.

I would also look to controlling the fans better with a PWM type variable speed controller which would also have a "soft" start feature. In this way the fans would essentially be running all the time, but at a greatly reduced speed when they're not needed. This would save wear & tear on the fan motors, starting relays, and wiring, by greatly reducing the number of start/stop cycles. It would also reduce the amount of noise they make, and it should help to control the deltaT across the radiator. DeltaT's in the cooling system are a big deal because if you have too much cooling going on, you can subject the engine to thermal shock and cause things like head gaskets to shift and start leaking, and/or the heads themselves to crack. At Caterpillar, we used to require our cooler providers to design for no more than a 15 degree deltaT between top & bottom tanks and then we would use a mixing valve arrangement for the engine thermostat to ensure the engines never saw more than 10-15 degrees deltaT.

[viabono]

Thanks for the explanation about the water. I've been following all these overheating threads because I figure its just a matter of time before I encounter something similar with my 550. My question about the water was in thinking you may have cavitation occurring at the water pump which is why my system 20+ years ago would not burp. Just enough air accumulated in the water pump after each heat cycle until cavitation started and because it was in the water pump housing, burping was not possible. Once we got the bubble out of the water pump we used distilled water back then because it was about as pure as you could get which in theory suggested to us that either it held less air and/or boiled at a higher temp which might prevent another bubble from forming in the pump where it was impossible to burp out. Whatever the actual science, the problem was immediately resolved and it never occurred again. We went through two water pumps, replacing/testing and re-replacing thermostats, hoses and on and on. In the end purging an air bubble from the water pump solved the problem and using distilled water seemed to help prevent it from reoccurring. Again, I'm not a mechanic and really should not be posting anything related to your problem, but you have run through all the logical paths to solve this seemingly simple problem so I thought I would post since it sounds so very familiar to my experience many years ago. Please post your findings when you get this sorted out.

[Granucci]

cribbj

I like the idea of shrouding the entire rear portions in a complete coverage draw. I also believe the wasted area from fan draw is not optimal and only relies on, what, air flow somehow? NOT really happening unless at 80+MPH. Such little design extra from OEM would have done that right IMO....scrimped.

Also, exit is limited IMO of these bays....

[cribbj]

Yesterday I installed a steam purge line from the thermostat housing to the expansion tank. This is a little mod that one of the good guys from the other site and I have been collaborating on (he designed and built the prototype, and I provided the pack mule service from the UK for the specialised parts )

It came out really well, and has made filling the system & purging air from it a doddle. Too, with the thermostat housing now being vented continuously to the expansion tank, it's nearly impossible for steam bubbles to be trapped in the system, even if/when the pump is cavitating. When I initially looked at the design of the 550's cooling system, I was surprised that Ferrari didn't include a high point purge line from the engine to the expansion tank, so I decided to add it:






After installing this line, I refilled the system, ran the car up to operating temps with the heater going full blast, topped up the coolant tank, then took the car out and got it up to its overheating temps and "shot" the radiator inlet & outlet with my IR gun:

Radiator inlet: 225 F

Radiator outlet: 218 F

This was last evening, after the ambient temp had dropped to "only" 95-96 degrees, but it was a good bit warmer than that in my garage where I shot the radiator.

The low deltaT and high outlet temperature, IMO, means the heat in the radiator isn't being dumped to the atmosphere fast enough. This now looks to be an air movement problem (fans).

If it were the water pump, I'd be having the same high inlet temperature at the radiator, but I should be getting a better deltaT across the radiator, with a much lower outlet temp.

Of course, it's possible to have both problems, which would also produce the symptoms I'm seeing!

Since the fans are known culprits in the 355 community, at this point I think I'll go ahead and get a new set and install them, however I'm guessing the car will probably still run hot under certain conditions until the ambient temps come down in September/October.

I believe the longterm, optimum solution is a new, larger radiator with a different type of fan setup, and I'll start working on that for next year......

[Granucci]

I like what I see on the vent.

I believe the fans, albeit, a bit more tricky in mfgr and install, will prove better than spending the time to jerk out the pump even if it can be done insitu. The air flow is key IMO. The water pump is most likely doing it's job and would have to almost toast to do otherwise ... IMO

[cribbj]

I now have a new set of fans for the car, so I took some current readings from the old set and one of the new ones this morning:

....................Starting Current.................Running Current
Left Fan:............49 amps............................15 amps
Right Fan:..........51 amps............................15 amps

New Fan:...........57 amps............................18-19 amps

So not a big difference in the old fan consumption and the new, however I'm sure the output of the old fans has diminished due to age & inefficiency, so I'm going to go ahead & install the new ones, although I'm now thinking this won't be the answer, but it'll be good insurance against a future failure.....

More interesting data; I measured the 550's radiator core the other day, and was surprised how small it was, in comparison to some other cars I own. The 550's radiator core is only 24.25" wide x 19.125" tall x 1.25" thick. That's only 464 sq inches of frontal area for a 475 HP engine, or 464/475 = 0.98 in2/HP.

I'm accustomed to seeing radiator frontal areas of at least 1.25 in2/HP for high performance cars, and much higher than that for racecars where the engines are stressed for a higher percentage of the time than on the street.

By contrast my other hotrod (a Toyota Supra) has a radiator core of 457 in2 for a 320 HP engine, or 1.42 in2/HP. This car has never had any overheating problems, although on 100+ degree days, the temp gauge does run higher than in cool weather.

Even my wife's car (a Chevy Suburban) has a mammoth 646 in2 core radiator for a 300 HP engine, or 2.15 in2/HP. This car has never had any overheating issues and the temp gauge stays glued on 210 degrees regardless what we throw at it. I suspect it needs such a huge core because the engine is working proportionately harder hauling around the 3 tons of steel Suburban plus 1-6 occupants.

So, I'm fast coming to the conclusion the cooling system in the 550 is just undersized. At least for running this car in 105-106 degree Houston weather and stop & go traffic

[Killer58]

Originally Posted by cribbj

So, I'm fast coming to the conclusion the cooling system in the 550 is just undersized. At least for running this car in 105-106 degree Houston weather and stop & go traffic

Sounds no different than your average British car of the 60s

[cribbj]

No kidding; this 550 reminds me of my old E type in so many ways.

Thankfully no Lucas electrics, though.

[tazandjan]

John- Just for your information if your new fans are not hacking it, Ferrari replaced the fans for the Superamerica with a new part number 208819. Not sure if they will fit a 550, but might be worth asking Daniel at Ricambi.

Taz
Terry Phillips