Unusual deposits on my inlet manifold | FerrariChat
Buy

Unusual deposits on my inlet manifold

Discussion in '308/328' started by GT4andMore, Aug 13, 2025 at 11:57 AM.

This site may earn a commission from merchant affiliate links, including eBay, Amazon, Skimlinks, and others.

  1. GT4andMore

    GT4andMore Karting

    Oct 23, 2020
    68
    Full Name:
    Graham
    #1 GT4andMore, Aug 13, 2025 at 11:57 AM
    I have been trying, and failing, to fix a poor running issue on my Euro spec 308 GT4 for many months. Symptoms are worse when the engine is hot and typically result in pops and bangs at higher revs. I have the cam covers off at present in order to check the valve clearances - all within tolerance - however with the covers off it is clear that I have some sort of deposit built up under the left hand carb, viewed from the back, on the rear bank which is not present on the right hand carb. Looking more carefully the left carb is also much dirtier and there is even a small amount of greenish liquid trapped in a well in the inlet manifold.

    History and intuition tells me that these things might be important and might indicate a leak or other imperfection in my input circuits. However I assume fuel would evaporate cleanly and there shouldn't, hopefully, be oil this far up.

    I assume liquid is dripping down from the carb onto the manifold but wouldn't rule out the opposite; with something leaking back out of the interior through the manifold gasket

    Interested if anyone has seen anything like this before and even better if this might be linked to some sort of helpful intervention. I am tempted to replace the manifold gaskets between the carbs, spacer and manifold.

    I have posted some photos below

    Any thoughts gratefully received.


    Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login
     
  2. Cameron Henlin

    Cameron Henlin Karting
    Silver Subscribed

    Jul 3, 2020
    155
    Roseburg OR
    Full Name:
    Cameron Henlin
    #2 Cameron Henlin, Aug 13, 2025 at 12:23 PM
    The greenish liquid there is coolant, and the deposits that you're referring to are congealed and crystalizing coolant. I would take a hard look at all of the coolant lines and fittings. If you're having problems identifying where the problem is exactly, you can put dye in to the coolant system and then look at it with a black light, which usually makes things easier to spot. Looking at the overall state of things there, I imagine you'll probably end up replacing all of your coolant lines
     
  3. Rifledriver

    Rifledriver Three Time F1 World Champ

    Apr 29, 2004
    37,153
    Cowboy Capitol of the World
    Full Name:
    Brian Crall
    #3 Rifledriver, Aug 13, 2025 at 1:03 PM
    You are in dire need of pulling both manifolds to fix the corrosion to both head and manifold surfaces. Last one I did the manifolds were so stuck to the corroded studs I had to remove the heads, rig them up in a drill press and drill out the studs with special vey long drill bits. The corrosion was so bad I felt lucky to save the castings. The corrosion worked its way well into the intake path sealing spaces.
     
    Cameron Henlin, Sergio Tavares and smg2 like this.
  4. smg2

    smg2 F1 World Champ
    Sponsor

    Apr 1, 2004
    16,368
    Dumpster Fire #31
    Full Name:
    SMG
    #4 smg2, Aug 13, 2025 at 1:25 PM
    This.. This right here..so much this.
     
  5. GT4andMore

    GT4andMore Karting

    Oct 23, 2020
    68
    Full Name:
    Graham
    #5 GT4andMore, Aug 13, 2025 at 1:35 PM
    Yep - spot on - struck me between the eyes after writing the post. So there is a coolant feed via a bridge to the centre of the two heads and I am guessing that feeds into heads via the inlet manifolds. Yep - spot on - there's clearly coolant coming back through the gasket.

    Will certainly remove the inlet manifolds and report back - hopefully much easier than that experienced by Rifledriver but if the heads need to come off - or the engine out - then so be it. It's a fun and interesting way to spend a few weekends.

    Is it possible that this explains poor performance when hot. Is it possible that as the coolant system comes up to temperature so coolant is making it into the inlet mixtures and suppressing ignition.

    Thanks - pleased I posted - looks like we are getting somewhere.
     
  6. Sergio Tavares

    Sergio Tavares Formula 3

    Nov 15, 2018
    1,319
    Full Name:
    Sergio Tavares
    #6 Sergio Tavares, Aug 13, 2025 at 2:15 PM
    Can this be prevented with more coolant changes?
    Sacrificial anode from boating supply?
     
  7. jmaienza

    jmaienza Formula Junior

    Jan 8, 2009
    629
    Massachusetts
    Full Name:
    Joe
    #7 jmaienza, Aug 13, 2025 at 6:49 PM
    Not changing coolant frequently can corrode the metal, especially in the intake manifold/cylinder head mating surface. I had a coolant leak similar to yours. Mine had major corrosion which I fixed by adding many layers of an aluminum filler then sanding to make it smooth. Eventually, i got it to seal with the gasket and the leaks stopped. You have to remove the intake manifold and check both the manifold and cylinder head surfaces for corrosion. Also, the gasket that goes between the intake manifold and cylinder head had a modification which adds new holes to better circulate the coolant.

    Image Unavailable, Please Login
     

Share This Page