F355 Coolant Rust and Fluid loss.

Ever since i have owned my F355 I have always had an issue with rust in the coolant expansion tank, which has puzzled me because AFAIK the block is aluminium, so from where its coming from I/m not sure...?

I have also had an issue with pressure buildup ( overflow cap leak) and loss of coolant on long drives, which I had chalked down to leaking radiators that were noted at the last major, and was a major PITA as I would find unsightly rusted fluid surrounding my expansion tank..I also changed my header tank cap to a new one.. no change..

Suspecting the rust was coming from the header tank, I removed it and cleaned out the rust it, and unblocked both nipples, but it was still happening. I also did a combustion chamber leak test on the coolant fluid.. all was OK.

Unfortunately I was unable to pressure test the coolant system as I don't have the correct coolant expansion tank plug for the F355, however I can confirm that both radiator fans come on and work properly. The leaking radiators was noted at the last major some years ago..

As far as the rust goes.. I am wondering if there is any benefit to doing a coolant system flush on the F355 using something like thermocure, as I want a pristine system before hoking up my new radiators and topping up with distilled water/coolant.?

As far as the pressure buildup/coolant cap overflow goes.. Is this normal for the vehicle..?
Whilst doing the combustion chamber leak test I noticed a fairly constant stream of air bubbles visible in the filler neck, which did not settle with time as expected..

I also noticed that the whole fluid level rises periodically ( at idle with the coolant cap off) and you get spill off of fluid even when the coolant level is no way near the top of the header tank..

Is this a common issue with this vehicle..?



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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?

 

From a cold start.
After 9 min of idle only.. ( no revving) , with the expansion tank cap off, I see the water level starting to rise as the thermostat opens.
What follows is a constant trickle of air bubbles and a rising water level that overflows every so often resulting in water loss into the engine bay.
You can see the rust in the water in the video..

Rust has been diluted a bit because I topped up the expansion tank for the demonstration..
When I first observed the rust it was twice as concentrated as in the video..
NB: HEVC video extension required to play MP4 video..

Leak in radiators is very small, but present ij both radiators as noted with last major..
Its so small no fluid is left on the garage floor overnight.


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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.

 

That's a disturbing thought..

I thought I excluded this by performing the combustion cylinder leak test in my first post..
The fluid remained BLUE even after something like 10 min.?1!?

Now I am scared to do the rev to 3k thing..

Can I ask other F355 owners if their expansion tank fluid does anything remotely similar to mine..?
Because as far as I am concerned, I don't think this amount of bubbles is normal..

 

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.

 

Yes that's what i have heard, that the F355 head gaskets are pretty resilient.
Still the amount of air bubbles and the fact that they don't go away after a few minutes is a real concern.
I tried the 3k rev thing.. and the water got pushed out the expansion tank more.


As regards the header tank.. it is my understanding that the expansion tank is steel.. and that's where the rust comes from.?! ( but I may be wrong)
That's why Superperformance offers an uprated aluminium version of the original..

https://www.superformance.co.uk/355/cooling.html

Still I would like to hear from other owners if this overflow of fluid at idle warm up is normal or not..
Anyone else getting air bubbles at idle..?

 

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.

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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 ...

 

Found a decent video that explains cavitation..



Watch the first 2-3min and at 9min.. You can see the destruction to the cylinder liner caused by improper coolant fluid..

 

Apart from the Snap On kit, which is pretty pricey.. cab anyone suggest a cheaper alternative to test the cooling system and coolant cap..?

https://www.snaponradiatortools.com/wp-content/uploads/2016/07/SnapOn_Application_Guide.pdf

Snap On Cooling System Tester SVTS263A
Plus the adapter caps TA26a. TA18B


I found this kit. But I don't think it has a means of testing the coolant cap..
The adapter that fits the F355 is the anodised blue one on the left.

https://www.ebay.com.au/itm/385567604978?var=653393195395

Its the 14 piece kit.. so I am wondering if the 28 piece kit also allows you to test the coolant cap.. ?

You can see the kit used on a 360 in this video..



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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.