308 QV - Correct Radiator / Surge Tank Cap

This should be helpful

http://www.ferrarichat.com/forum/308-328-sponsored-yellow-compass-group/481195-check-your-radiator-caps-now.html

 

If you REALLY want to be correct, buy the 0.9 bar cap.

I may be wrong but I believe the 0.9 was stock but as years passed we have found the 1.1 to be more effective, at least on the QV.

Try T Rutlands

 

Read that link Tommy provided.

As I understand it, there was a Factory Service Bulletin issued some years after the car was built specifying a change to a 1.1 bar cap from the original 0.9 bar cap.

The four-eared Stant 10231 looks very similar to the factory cap. Its a 1.1 bar cap. Shop your big box aftermarket automotive parts stores. They should be dirt cheap, like $10.

It's what I have on my car now. I have an original Italian-made 0.9 bar cap which I was "saving" for concours events just to look cool. I entered my car at Concorso Italiano this year and forgot to put on the cap. The judges did not (and should not) care.

 

Mine's a '84 QV (Euro) and I tried a 1.1bar cap and after a relatively short drive (~ 15 miles), coolant was spewing from my overflow tank (never did this before). I had my 0.9bar cap with me, swapped, and the coolant spewing issue went away.

 

My impression is your 1.1 bar cap was most likely defective from new.

That is the only way that makes sense.

 

The Stant 10331 Red release lever hits the Metal mesh under the lid when closing on the 328 so you ave to use the 10231 Cap.

 

Exactly what happened to me. Don't know why the 1.1 bar would spew coolant and not my old .9 bar. Anyway, .9bar is on now and no spewing.

 

I had to do the opposite.

That pic on my thread linked here is of a 1.1. I bought that (specifically) because my 0.9 was spewing. I had that 1.1 cap for 17 years.


The common denominator in all our cases is the factory cap, be it 1.1 or 0.9. Like Rifledriver has said many times, they are crap anyway so none of this surprises me very much.

 

No offense intended to those that had this problem, but I agree with Dr. Tommy - the only way a 1.1 bar cap spews and a 0.9 cap doesn't is if the 1.1 cap is defective - not tightened correctly, weak or broken spring, etc.

As noted by Brian A, and previously by RifleDriver, Ferrari issued a Service Bulletin with the recommendation to change to the 1.1 bar cap, so that is the proper specification since the mid-80s.

 

1.1 BAR cap is 137644. Agreed, a spewing 1.1 would be a defective or failed cap.

We have the STANT and original ones here: Search results for: '137644' - Ricambi America, Inc.

 

This is what most guys in the club over here are running to replace their original 30 year old cap while keeping with the OEM look.

New OEM Ferrari Radiator Cap 4 ear 0.9 BAR for 308 Mondial Testarossa 328 512BBi | eBay

I have the 0.9 on my car and works like a charm.

 

The flexing from expansion will cause a leak in all of them after a given number of cycles in the stiffening grooves as you describe. Any rust will accelerate that and they rust worst on the upper surface where you cant see it. No repair will be permanent. Get a new one.

 

If Ferrari had a factory bulletin in the mid 80's going from 0.9 bar to 1.1 bar, why would my 1988 3,2 Mondial model have had the 0.9 bar cap from new? It was original, I have since replaced a few years ago with an identical (but for a date stamp) four ear 0.9 cap just because of the age. But I don't know what problem the factory was solving for on the QV's other than maybe some markets had higher elevations and 1.1 bar across the board made sense for them as a manufacturer? But if it works, surely using the lower pressure than higher one makes sense. I suppose the pressure-difference between 0.9 and 1.1 is not very big, and the range for the caps is +- a bit anyways.

There are threads on this, but unless I missed it, other than using 1.1 or the Stant equivalent being a common practice by those with experience, which I would defer to of course, I am not sure why one would prefer one verses the other but would think 0.9 is better if your car otherwise works fine at this lower pressure?

 

Doc, since my .9bar is holding the pressure just fine, should I replace it again anyway or is it,
" if it's not broken don't fix it"?

 

Leave it alone.

QV's cooling systems are an enigma to me. Some run too hot in traffic (mine), others are just fine.

Some blow past a 0.9 (mine did) others, like yours, don't.

I cannot think of any reason in the world to change psi ratings if you are not having a single problem.

 

What is better about low pressure? Higher pressure is a higher boiling point and helps prevent cavitation that destroys wetliner engines.

Do any of us really believe we know better than the entire world of automotive engineers?

If you want to live in the 20's and really like sitting on the side of the road boiling over that's fine but leave me out.

I'd raise it to 30lbs if I thought the radiator would take it.

 

On second thought, Mike, maybe you should go ahead and grab a 1.1

 

I guess you're right Doc just to be on the safe side assuming I'll get a good 1.1bar this time.

 

Running Evans coolant with 0 pressure actually seems like a good idea, using modern chemistry rather than reverting back to the 20's!

Was there actually cavitation problems and engine liner damage, so the factory upped the pressures? That would be a serious problem, so I am just curious if that was actually happening. Certainly would explain why they raise the pressures.

OEM's spec pressures from as low 5 to 42 (eg. Inifinit Q45), so higher is not better, it is clearly design dependent. Although most are at the 13 to 18 psi rating for sure, so 1.1 bar (16psi) would certainly be viewed as typical.

Upping pressure a bit, and gaining about 10 degrees of boiling point seems pretty benign. But as my owners manual states the system is under 12.8psi (0.9 bar), with a designed max temp of about 240 degrees and with no (known) issues in my instance, I would be staying with the factory spec.

If I am boiling by the side of the road, I will remember this thread!

(That said, I recently replaced the coolant hoses under the plenum, no doubt originals, after noticing them bulge out like something I had never seen, normally I would not be inspecting the engine that closely while it is running, but one time I was looking and got out my lighting and thought, yikes that can not be normal! These were the first hoses I have ever seen on the verge of failure like this in my life. So for all the fuss on rad caps, I suspect a burst hose will more likely be the reason for boiling over on road side!).

 

My tank bulges on the top as well but no leak for all these years. Changing back to 0.9 bar this major service and will see if it causes any trouble at all.