F355 Coolant Rust and Fluid loss.

It will be hard to diagnose the cooling circuit with leaking radiators.
Could you post a picture of how the "rust" in the header tank looks like?

 

It looks to me like a sign of leaking cylinder head gasket(s) or, possibly, a crack in cylinder head allowing combustion gasses to be pushed into the cooling system.

A way to further test this is to, while you have the bubbles coming out of the coolant filler neck like shown on your video, you briefly rev the engine to some 3000 rpm or so (keep a bit away from the filler neck). If the coolant is briefly pushed up stronger with many more bubbles coming out, it will confirm the mentioned suspicion.

 

Expansion tank is aluminum and cannot rust. There is also a heat exchanger that can leak from gear oil to coolant and that would change coolant color. As for head gaskets, I rarely see head gasket failure in 355.

 

Not enough data given to diagnose but rust in coolant can be from poorly maintained coolant systems. The 355 is a wet liner motor. A small number of the fleet have reported liner cavitation. This is a well know problem in diesel motors prevented with coolant additives. Rust in a 355 is most likely from the wet liners. Cavitation increases rust. Cavitation occurs more naturally in diesels due to operational and design character of the motor. But those cavitation properties can be replicated with various operational faults in any motor. Some manufacturers spec coolants to deal with these possible issue like coolants with nitrates. Zerrex G05 (there are many others) is a generic coolant used in diesels for this reason and perfectly compatible with a 355 motor. I use it in my 550 and actually all my cars so I only have to stock one coolant. It might be a bit overkill because we do not have cavitation in the fleet but I have seen 1st hand some cavitation damage during some ferrari engine rebuilding. Simply a poor factory liner can increase cavitation and rust. The post mentioned coolant loss and the 1st thing I think about is pressure cap failure. This cap design is very poor. You can buy a dozen caps from Ferrari and about 6 will hold pressure....for now. I gave up on Ferrari caps convert to standard tried and true. Lack of system pressure allows air in system and increases rust. Lack of pressure increases potential cavitation. Unprotected liners lacking a sacrificial nitrate coating increases potential cavitation and exposes liners to coolant water increasing rust. We don't see NOS water pumps. Many are remanufactured. some are owner/mechanic rebuilt by part replacers. I have seen new rebuilt pumps scrape pump housings on install. I have seen warp in plastic impellers. No one I know who replaces a pump checks the clearance of impeller to pump body. How can a water pump increase your rust? Improper flow increase overheating increases cavitation potential. It is not enough to change coolant for maintenance. You also need to make sure the cooling system is functioning optimally and that the motor runs optimally because the whole thing functions as a system. Diagnosis starts with a cooling system pressure test. A blackstone coolant test will tell you what is in your coolant. Is that rust or other contaminant?

 

“ I gave up on Ferrari caps convert to standard tried and true.”


So which cap do you run?

 

For comparison, observing the coolant level in open header tank of a good engine, the coolant level will, during warmup, slowly climb up somewhat due to thermal expansion, no bubbles, and, when the engine is revved, the coolant level will move down a bit (and return to previous level when the revs settle down back to idle).

 

Tank is aluminum in 550. I cut off old bung and welded on billet aluminum bung from Canton. Now I can use standard radiator caps that never fail in correct pressure. I cut the inside of a Ferrari oil cap and friction fit the replaceable radiator cap. Now my coolant, oil and fuel caps are all the same. That's the way Ferrari should have done it.

Image Unavailable, Please Login Image Unavailable, Please Login

 

That’s definitely interesting.

 

@fatbillybob

You mentioned you pressure tested roughly a dozen brand new “Ferrari” caps and only half were good? That’s an interesting data point. What tool did you use to pressure test it? Snap-On adapter?


Ferrari doesn’t make these caps. They’re made by MTA, which I believe have switched manufacturing to Brazil for the past decade. The original ones, which also have a different appearance were made in Italy. “MTA Italy.”I believe those hold up better for whatever reason.

I wonder if this switch to Brazil manufacturing is the leading cause of why newer type MTA caps are losing pressure after 1-2 years and recommended to be replaced more often.

Another 355 owner in UK stumbled upon coolant caps which highly resemble the older/original MTA caps, but they are not made by MTA. However, they are manufactured in Europe. Fits 355 perfectly (should work for 550 as well.)


I purchased 2 new style MTA Ferrari caps. I tested one and it lost pressure. Didn’t bother to test the other one. I have the “original” one still on the car, which I assume is 30 years old and it holds pressure better than the new cap, which has never been used. Go figure.

 

I don't know why those caps suck. They just do. Caps need to allow build-up of pressure then pressure relief at rated pressure and hold rated pressure. So a cap can have a few failure points. Something as insignificant as a cap can cause a lot of trouble.

 

Very few of us can tig-weld ...

 

Nice find!

Unfortunately, the Snap-On TA26a adapter is really the only adapter I found to test coolant caps. Maybe someone can rig something up, but doesn’t look like the kit you provided has something… unless one of those threaded adapters happens to fit our coolant caps.

 

Cavitation in engine cooling system is primarily caused by insufficient system pressure (the cap) and not really by the type of coolant used. Inadequate water pump design can also contribute to cavitation, especially at higher rpm.

 

Checking for cooling system leaks may not give you conclusive results. If, for example, a cylinder head gasket is leaking at the flame ring, the cooling system pressure test may show no leaks because it is done at low pressure (around 20 psi ?). Acting in the opposite direction, the combustion gasses will pass through the faulty section of the flame ring because they are at extremely high pressure (peak at 1000 psi or more).

Based on the facts that your coolant is pushed up (when it is not boiling), has many bubbles coming out and it is very much of the same colour as what the video in your post #16 shows, it seems to me that there is a leak somewhere of the combustion gasses into the cooling system.

 

I don't know if it's doable on that engine but perhaps try to flush the whole coolant circuit by getting continuous flow, simply with tap water from the garden hose, up from the coolant tank down to the bleed holes on either side of the block. On a more simple engine with an iron block this method allowed me to get all rust residues out of the circuit in no time.

 

If you get bubbles and the coolant level rising soon after the start of a cold engine, i.e while the engine has not fully warmed up, observing while also revving the engine, then the symptoms you are having are not due to the coolant boiling.

As to the CO2 test, when I once investigated coolant loss (being pushed pass the pressure cap) on my Daimler Super V8, the gas tester showed no CO2 when I did the test at idle after starting a cold engine and after letting it warm-up. Then I repeated the test after driving the car for a while, letting the engine cool down just sufficiently so that I could carefully remove the header tank cap. The tester clearly showed presence of CO2. I found that both head gaskets had leaks at some of the flame rings.