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355 Thermostat replacement DIY?

Discussion in '348/355' started by Targatime, Apr 29, 2023.

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  1. Targatime

    Targatime Formula 3

    Feb 22, 2014
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    #1 Targatime, Apr 29, 2023
    I need to replace my thermostat (engine runs too cool on the highway) and looking things over one thing I'm not sure of is whether I need to drain the coolant to do it. The thermostat is up high at the front of the engine; maybe the coolant level when the engine's cold is low enough that opening it up won't make a mess in this location. Anyone know?

    Any other general tips are appreciated, I haven't done this before and most of my wrenching experience is from air-cooled 911's. Looks pretty straightforward.
     
  2. Qavion

    Qavion F1 World Champ
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    #2 Qavion, Apr 29, 2023
    I can't imagine it would be too easy with the fuel rail/block above it (?)

    Do you have an OBD2 scanner which will let you look at the temperature that the Motronic (5.2) ECU thinks it is? If the temperatures are similar, at least you know your gauge is reading correctly.
     
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  3. GatedF355GTB

    GatedF355GTB Karting
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    #3 GatedF355GTB, Apr 29, 2023
    It’s not a hard job. If memory serves, I didn’t bother draining the coolant. You’ll get a little spillage but I was able to minimize that with a small cup placed under the hoses when I detached them. The hardest part is crawling up there to access the part.
     
  4. GatedF355GTB

    GatedF355GTB Karting
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    #4 GatedF355GTB, Apr 29, 2023
    Forgot to mention however that my car is a 95 (pre fuel block recall)
     
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  5. Targatime

    Targatime Formula 3

    Feb 22, 2014
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    #5 Targatime, Apr 30, 2023
    I don't -- I thought that was only possible with the factory computer? I highly doubt my problem is not the thermostat. Radiator fans come on exactly when they should. Engine never runs hot. But hit a higher-speed stretch of road or the highway, where air is flowing over the radiators, and engine temps drop down around 160F. Come right back up once you slow down. It's totally dependent on MPH. How could this not be the thermostat sticking open?
     
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  6. GatedF355GTB

    GatedF355GTB Karting
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    #6 GatedF355GTB, Apr 30, 2023
    A good way to tell is to observe how long it takes for the car warms up from cold. The car should reach normal operating temp in a mile or two. If it takes longer to warm up, the thermostat is probably stuck open which is the failsafe position.
     
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  7. Targatime

    Targatime Formula 3

    Feb 22, 2014
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    #7 Targatime, Apr 30, 2023
    In terms of the R&R, I just took a closer look and I think I will need to disassemble the fuel block and drain/remove the PS reservoir. It looks like if I disconnected the fuel lines from the rails I *may* be able to move the block/reservoir assembly out of the way, but it won't move much and it's probably easier in the end to just get them completely out of the way. Especially since this is the hardest part of the engine to reach (has anyone rigged up a harness/pulley system so you can suspend yourself over the front of the engine?) Was hoping to avoid a gasoline/PS fluid/coolant mess trifecta but looks like it's not really possible. Terrific.

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  8. johnk...

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    #8 johnk..., Apr 30, 2023
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  9. Qavion

    Qavion F1 World Champ
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    #9 Qavion, Apr 30, 2023



    Why not let your dealer tech do the job (and he'll throw in the fuel block upgrade for free). Having said that, he'd probably charge you standard prices for the thermostat change (even though that would kill two birds with one stone).

    Not sure... My scanner only reads codes.
     
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  10. lanab

    lanab Formula Junior

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    #10 lanab, May 1, 2023
    The free fuel block upgrade is past due, they are not paying for that anymore, i replaced mine 2 years ago and it was a no from Ferrari.
     
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  11. yelcab

    yelcab F1 World Champ
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    #11 yelcab, May 1, 2023
    You will make a mess but that is OK.
    Drain the coolant from the radiator, and remove the coolant tank
    Remove the PS reservoir after sucking out the fluid.
    Remove the two fuel lines attached to the left of the fuel block, and swing the fuel block out of the way so you can see the thermostat housing
    Loosen the hose clamps on the large 40mm hose between the thermostat housing and the large pipe running between the two radiators.
    Remove the thermostat housing, and the themostat
    Revere process, fill up with coolant.
     
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  12. yelcab

    yelcab F1 World Champ
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    #12 yelcab, May 1, 2023
    My scanner with live data capability reads a number of data streams including the coolant temperature seen by the CPU. It does not work on 95 OBD1 types.
     
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  13. Zamboniman308

    Zamboniman308 Formula Junior

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    #13 Zamboniman308, May 1, 2023
    Sounds so easy lol. And it isn't hard but considering I'm knee deep in similar work you forgot all the cussing and swearing involved.

    If working on a spider pulling the engine deck lid and standing in the car may be helpful in getting at the areas.
     
  14. Zamboniman308

    Zamboniman308 Formula Junior

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    #14 Zamboniman308, May 1, 2023
    And the block recall kit is no longer available from Ferrari. So you need to find a dealer that is sitting on one.
     
  15. Targatime

    Targatime Formula 3

    Feb 22, 2014
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    #15 Targatime, May 1, 2023
    My car runs way cooler than that, around 160F. There is definitely a problem.

    Thanks all for the advice. Re the updated fuel block, my understanding is the only thing it does is change the angle of the fuel lines on the left side so there is more clearance of that coolant hose clamp. It's otherwise not a stronger/different product? If I can't find one, then no biggie I would think, since I have the hose clamps far away from the fuel lines. So I guess my new while-you're-in-there list is:

    Fuel block update (if available)
    New fuel lines (any update @MR-DW? This one will probably have to wait)
    Thermostat replacement
    Coolant flush
    New coolant temp sensors
    Gear oil/coolant heat exchanger delete (this thing is a disaster waiting to happen)

    I would add clean/grease the throttle bellcrank to this list but I already did it (it was surprisingly sticky and rusty on my lifelong southern California car)

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  16. johnk...

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    #16 johnk..., May 1, 2023
    Last edited: May 1, 2023

    177* may not be right. I would compare the position on the gauge. Seems according to the poll most cars run around here on the highway.

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  17. Targatime

    Targatime Formula 3

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    #17 Targatime, May 1, 2023
    Thanks for the pic -- I will dig up the pic of where my temp gauge sits on the highway, I took one a while back when ambient temps were in the 80's F.
     
  18. Skippr1999

    Skippr1999 F1 Rookie
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    #18 Skippr1999, May 1, 2023
    I changed my 355 thermostat and broke a rib while leaning into the engine bay. It was about 6 years ago and with fading memory, that’s all I remember.

    I’m pretty sure I didn’t drain coolant or power steering fluid. Just moved some stuff around to get access. Watch your ribs.
     
  19. Targatime

    Targatime Formula 3

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    #19 Targatime, May 1, 2023
    Ok here is a pic I took of the water temp on the highway (back before my car became a manual). This was on an 85 degree F day. I can't make heads or tails of what the hash marks on the gauge mean (why did they do it like this? ridiculous design) so I don't know exactly what temp this is. But it looks well below 177F to me.

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  20. Targatime

    Targatime Formula 3

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    #20 Targatime, May 1, 2023
    Per Goth's thread from years ago, my gauge is indicating a water temp in the high 160's.

     
  21. Zamboniman308

    Zamboniman308 Formula Junior

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    #21 Zamboniman308, May 1, 2023
    Before I'd tear anything apart I'd get an OBD scanner on it and read what the motronic thinks the temp is. Assuming this is a 5.2 car. I wouldn't trust the gauge without the other info.

    Decent scanners are so cheap anymore that I consider it mandatory equipment to have in the 355 pretty much at all times.
     
  22. Qavion

    Qavion F1 World Champ
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    #22 Qavion, May 1, 2023
    It looks like they just painted new numbers on the celcuis scale

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    50C = 122F
    60C = 140F
    70C = 158F
    80C = 176F
    90C = 194F
    100C = 212F
    110C = 230F
    120C =248F
    130C = 266F

    Your gauge is reading around 77C = 170.6F
     
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  23. Targatime

    Targatime Formula 3

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    #23 Targatime, May 1, 2023
    It is a 5.2 car, but is this really necessary? The fan comes on at exactly 190F on the gauge, which is the temp that should trigger it. If the gauge was off, that wouldn't be the case, right? I have an IR thermometer, I will shoot some temps next time I drive it.
     
  24. GatedF355GTB

    GatedF355GTB Karting
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    #24 GatedF355GTB, May 1, 2023
    The only way I could tell that my t-stat was bad on my 95 was a slow warm up. Hard to tell just looking at the gauge during normal driving - at least in my case.
     
  25. Zamboniman308

    Zamboniman308 Formula Junior

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    #25 Zamboniman308, May 1, 2023
    I just think it eliminates uncertainty. There may not be anything wrong. It also gives a glimpse into how well everything is operating.

    I think mune runs about where your photo shows when im rolling with good airflow. Closer to the 190 when stuck at a standstill.
     
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