F355 Oil Pressure?

No it is not

 

What happens to the pressure once started ? If it stays max it could be as simple as a dodgy connection if I remember correctly

See second half of this thread for example https://www.ferrarichat.com/forum/threads/f355-oil-pressure-high.670298/#post-148926541

 

Yes, that looks like a bad wire connection to the sending unit, the wire is shorted to ground, or the sending unit is broken and sending a maxed out signal to the gauge.

 

Pegged to max usually means the connection on the oil pressure sender (under the filter) has come off (and not shorting to anything). Unless the value changed when warm.

 

It’s not normal at any temperature. Possibly a faulty Thermocouple ECU. You just have to figure out which one is faulty. There are usually 3 on 5.2 cars. If the car has had a recent engine out service, perhaps the wrong thermocouples have been hooked up to the wrong thermocouple ECUs (behind the rear bumper (right hand side).

You can buy cheaper aftermarket units from Technistrada to help with diagnosis. You may need a wiring diagram to help you figure out which thermocouple ECU is which.

 

Re. Oil pressure: before guessing/hoping it is an electrical fault and potentially wrecking your engine, a proper technician would attach a diagnostic oil pressure gauge to the engine, read the real oil pressure and take it from there. You can even buy cheap-o testers like this…

https://www.amazon.com/DASBET-Engine-Cylinder-Pressure-Diagnostic/dp/B07GFL2GFL/ref=mp_s_a_1_18?crid=30HUYLZQMSCML&dib=eyJ2IjoiMSJ9.IUnYf6fZcnhRYPPeB8H3tYipIeodcnsMkeDkGwQeSSkI_PvqWZlJvMBeir2KjfXnopYrFtdZKthpi9KcDlMcJu6czEoiysFIb_Vg7b1Q68_ikqOJ6r-l-cRmOVK_KZryZLQorNRL86e9_p_tTulcZw1QDld9qoeh5H34TuLzrjM393XZrCzQN7fijt-u7BB1Ir8jZo_jBH-RW0qH6_Tl3w.qWNU0AmfQuTdFLB5IsreajuCVDQaGOczrLUYanZK3Sk&dib_tag=se&keywords=car+engine+oil+pressure+tester&qid=1733558276&sprefix=car+engine+oil+pressure+tester,aps,250&sr=8-18

 

If the slow down light comes on under normal driving conditions, that typically means one or both of the catalytic converter ECU's has failed. On the 355, they had issues where the housings on the cat ECU would separate around the edges and water (from a car wash particularly, for example) would get in and fry the circuit board. When this happens, you get that "slow down" light flashing at random times. On my 355, specifically, I had to have both my left and right bank cat ECU's replaced (luckily under warranty at the time). Who knows what the replacement cost would be today, but I'm sure it would set you back several thousand dollars at your local Ferrari dealer.

The early 355's also suffered from issues with their exhaust manifolds failing (especially the left side one if I remember correctly). My car was a 1997 model year and it had this issue. I believe the manifolds were either are prone to cracking and/or the air injection would burn a hole through them or something. I don't remember all the details, but I remember at the time it affected such a large number of 355's in North America that left side exhaust manifolds were back ordered for something crazy like 2 years at one point. When this failure occurred on my car, my friend (who was a service technician at Ferrari of Los Gatos) took me around back and showed me all the old warranty manifolds they had replaced; they were stacked up in a pile clear to the roof (there must have been 50 or 75 of them). He told me either I could wait for 15 months to have it fixed with a replacement part from Ferrari or they could just weld the hole shut if I left the car over night. I opted to have the manifold welded shut and that fixed the exhaust issue. I will say that when that failure occurred on my exhaust manifold, the exhaust note went from being a wonderful F1 sound to basically what a VW bus sounds like with no muffler on it.

I believe some of the early cars (1995 and 1996) also suffered from valve guide issues, although I don't know all the specifics with regard to that.

A manual 355 is a super fun car and the V8 w/ a Tubi exhaust sounds about as close as an F1 car as you can get on the street. Keep in mind that while the 355 is a super fun car, it's almost built like a kit car in some respects. As they age, things start to wear and fail and require attention. I mean on my car several parts just plain fell off with normal daily use. The dead pedal came off on my way to dinner once and another time I drove back, shut the door and part of the door just fell off on the ground. The leather in the car also had a bad habit of shrinking and pulling away in certain areas.

Additionally, at least on my car (and some others I knew of as well), they build up this strange "fog" inside the windows over time. I think it's off gassing from whatever glue Ferrari used on the inside, but who knows. I don't remember if it ever stopped on my car, but every few weeks you'd come out and if you left the windows all rolled up, then the inside of the car had sort of a hazy layer inside on all the windows which needed to be wiped off.

Also, be very careful on a cold morning if you fire the car up and give it too much throttle when the rear tires are still cold. The 355 requires some level of skill to drive and is lacking most all the modern electronic traction control measures you see on later cars; as such spinning your car or losing control of the rear end is a bit more likely under some situations. With my 355, several times the back end got away from me and I came very close to totaling the car (or at least doing great bodily harm to the body panels). If the rear tires are not fully warmed up to temp, be extra careful with the throttle.

As far as the oil gauge, I would guess either the gauge itself is broken or the sending unit is shorted out or dead. See if the gauge returns to zero when the power is off.

The 355 also runs pretty hot in the engine compartment area, so the rear challenge grill is a nice upgrade and allows quite a bit of heat to escape while driving.

How many miles are on the one which you are looking at?

Ray

 

For the main cats, ECU bypasses can be installed, such as those from Technistrada.

https://technistrada.com/dummy-load-sdl-bypass---not-for-installation-into-vehicles-equipped-with-catalytic-converters

 

Ciao Mauro. If you go over to the 348/355 section of F.Chat or play around with the search function you will find more than 20 years of knowledge covering every conceivable aspect of the 355, including hundreds upon hundreds of posts relating to oil pressure, pressure guage, pressure sender and so on, not to mention buying, selling, owning and just about any question you can think of

 

Oil pressure should vary on the gauge with engine RPM's as I recall yes.

If the car is owned by a mechanic, it's a little alarming that there are no clear service records as to stuff like oil changes, etc. Also, the fact that it's currently being driven around with several issues makes me question what kind of mechanic this is exactly. On my cars, I keep thorough records and as a rule fix things when they break (such as oil pressure gauges, etc.).

Given the age and miles, I think I would do more digging myself. Perhaps even a compression check and/or leak down test would be in order. Again, stuff like guides and things are potential sore points on the early cars (from what I understand).

Have you driven the car yourself and gotten a sense of how it performs? When the 355 is in good mechanical condition, it's very fun and easy to drive. Once you warm it up for a few minutes, it's as easy as driving a Honda or Toyota around town basically. Great car, but you definitely want to find one which has service records and has been well cared for its entire life as your starting point here. I would also inspect the under carriage for leaks, etc.

Ray