F355 - Bad Thermostat

"Chan - Mid-engine with cabin fever" (superchan7)
02/08/2016 at 03:56 • Filed to: Ferrari, F355, 355, 355F1, Thermostat, Maintenance

For the past few months, my F355 had been dogging me with temperature problems. Upon hearing this, a curious car guy could respond with the following typical questions:

Did it overheat?

Did it melt?

Did your kid put too many fingerprints on it?

Did you put too many miles on it? (i.e. over 10,000)

!!! UNKNOWN CONTENT TYPE !!!

Actually, the car had been running too cool .

The coolant temperature is supposed to remain between 170F and 190F (77C - 82C) depending on my driving. At idle, it jumped around between 150F and 190F. At steady highway speed it stayed consistently lower than 150F, with occasional oil pressure spikes which worried me. Oil pressure is supposed to remain just under 70 psi at steady speed.

The correlation between high speed and cold coolant told me that the thermostat had clocked out and was no longer closing properly. Too much coolant was being sent to the radiators by the thermostat sitting open. Driving the car hard and using the higher revs would probably not be good for long-term health since the oil viscosity is not optimal.

So, after reading various FerrariChat threads which mostly agreed that the original thermostat was:

A ripoff at over $300, and

Not very durable,

I ordered this thing from a shop in Arizona for less than $60 shipped:

Despite its janky appearance (it actually looks worse than the bad one that we eventually fished out of my car), this thermostat is fairly well-received in the F355 crowd. Behr Thermot-Tronik Italia made this aftermarket unit for certain Italian cars (among them the Fiat X1/9, Ferrari 348 and F355). A crude stamping reading “4M 82" denotes the proper 82C threshold.

I failed to find any sort of part number or model number aside from the above text, so I have no idea whether Behr still makes these. The packing slip was not much more helpful, reading “NON O.E.M. THERMOSTAT”.

Anyway, it was finally time to get my hands dirty on this car, in a mechanical way. With the help of an expert friend and fellow F355 enthusiast, we replaced the thermostat in just under two hours. It’s tucked all the way to the forward side of the engine (near the belts), buried deep under a bunch of other plumbing.

Let the car cool down for at least 1 hour. We did not do this, and in a later step I will explain why that was a bad move.

Relieve coolant and fuel pressure (open gas cap and open coolant expansion tank cap)

Remove rear bonnet. This is a 2-person job due to the unwieldy size. Total of 4 bolts.

Remove the decorative central engine cover between the two intake manifolds. 2 of the screws are different from the other 4—sort all the screws, washers and bolts. Everything is metric.

The fuel distribution hoses and 2-to-4 fuel distribution block are in the way (braided steel hoses—there are 6 total). Disconnecting them, we got random sprays in the face by residual pressurised fuel in the hoses. Lesson: Let the car cool down longer.

The power steering fluid reservoir is in the way. Remove its mounting screws—a pain due to other hoses in the way. Remove its metal mounting bracket and tilt the tank rearwards:

Now we see the thermostat housing (below, red arrow). Remove the short but nearly 2" thick coolant hose feeding the thermostat housing (below, yellow arrow). The better half of a gallon of coolant will puke out. Cost of doing business.

Remove the thermostat upper housing, 3 nuts. Now the thermostat is exposed, as shown below. It’s flooded in coolant, so take it out carefully. Move the original rubber seal to the new thermostat.

Re-assemble everything by going backwards.

Replenish the lost coolant. Using the expansion tank opening and a pressure tester, test the car for leaks.

Clean up the engine bay—by now, that fuel spray should have long evaporated. Start the car, and check for leaks.

Re-assemble the engine bonnet before the engine bay gets too hot to bear.

Car runs like a charm now, with good temperature and steady oil pressure. Mission accomplished, right on time for the Lunar Year.

DISCUSSION (8)

slipperysallylikespenguins > Chan - Mid-engine with cabin fever
02/08/2016 at 04:19

cool write up, its interesting to see the mainteneance on more exotic vehicles. Kudos for doing it yourself

Rusty Vandura - www.tinyurl.com/keepoppo > slipperysallylikespenguins
02/08/2016 at 06:25

$300 for a thermostat... How much for an oil filter? This is the sort of thing that people do NOT think of when they spot a Ferrari and say, “Wow! A Ferrari!” Congrats on your accomplishment.

Chan - Mid-engine with cabin fever > Rusty Vandura - www.tinyurl.com/keepoppo
02/08/2016 at 14:27

An OEM parts supplier lists the F355 oil change kit at $52. It contains the filter, its hardware, and a few other plugs and rings for the dry sump tank and the oil drain.

Rusty Vandura - www.tinyurl.com/keepoppo > Chan - Mid-engine with cabin fever
02/08/2016 at 14:56

Wow; that’s downright reasonable!

Chan - Mid-engine with cabin fever > slipperysallylikespenguins
02/08/2016 at 19:25

This was a small job, plus it’s just one of the suspects in troubleshooting abnormal temperatures—there may be other suspect items such as the gauge itself and the gauge’s coolant line temperature sensor.

The primary motivator for DIY is to avoid the specialist mechanic that I usually go to. For any form of troubleshooting, his backlog is about 2-3 weeks before my car even gets touched.

Nauraushaun > Chan - Mid-engine with cabin fever
02/13/2016 at 17:38

I’m not sure how I’d feel if the OEM parts for my car were both expensive and shit. There’s a pride in using OEM parts, even in paying the premium that goes along with it. But if those parts are shit it would make me feel uncomfortable about the company that made the car.

Chan - Mid-engine with cabin fever > Nauraushaun
02/23/2016 at 16:46

In general, OEM parts tend to be better on mass-produced car as they are engineered for longevity over beginning-of-life performance. The pride in using OEM parts comes from the fact that most of the time they are indeed the best solution . But with 20+ years since the development of the F355, it has become very easy (and cheap) for someone in 2016 to out-engineer a 1990s OEM part.

One example is the F355 water pump. The OEM one lists for $700+ and has a plastic impeller. Someone in the US designed an all-aluminium one. It now sells at a major online Ferrari parts distributor for $350. This distributor is so convinced that it even recommends against buying the OEM unit.

Other parts, such as the headers and catalytic converters, were badly specified by Ferrari and could not withstand the heat of normal operation. They are just crap and belong in the trash.

Nauraushaun > Chan - Mid-engine with cabin fever
02/23/2016 at 19:32

That’s what I’m talking about. OEM parts that are crap and belong in the trash, it’s depressing!

I’m all for someone designing a better part 2 decades later :)