Cooling system bleeding procedures

Morning Gents,

I realize that this topic has been beaten to death on the "other" board...but I want to ensure that my procedure is sound.

Here's the starting point:

-365BB-Fresh engine, with re-built water pump
-Impeller to front pump housing clearance reduced from factory spec of 1.6mm to 0.3mm
-BB512i 79C deg thermostat upgrade
-80C deg thermofan switch
-5-blade fans upgrade
-30% Honda anti-freeze (no silicates/borates) with WaterWetter
-1.2 bar OE cap

At 75F deg: Water temp on highway 72C, City 80C

Although I don't have a hot running problem...she'll leave a trail of coolant from the overflow tank after driving awhile around town. Sometimes, but not always.

The cap tests good....
The car clearly is not overheating...as both oil and water temps don't exceed 80C in town.

I've bleed her warm and cold...(Engine off-Remove overflow tank cap....crack bleed until air stops)
Heater valve is open.

Possibly she's still seeking her own "natural level" in the oveflow tank?

Thoughts, anyone

David,

of course I have my way of bleeding the Ferrari Cooling Systems because one finds out early on in a carreer that certian cars just like being difficult and uncooperative.

I don't have any tricks other than the paitience to play with and fuss over the engine while the whole process plays out.

First rule as you know of course is that the coolant level should remain as high as possible in the Header Tank to facilitate Gravity Feeding. Second thing is cap should be off to prevent a vacum from forming anywhere in the system.

I start with cold/warm engine with the cap off, coolant close to the brim, heater valve open and car on flat ground or if in a driveway slightly inclined in the front is ok. Then I just start the engine and let it begin the process of gravity feeding and pushing the air into the radiator to be bled off at the bleeder valve. The process takes quite some time as it's neccesary to run the engine until well after the T-Stat has opened and the fans have begun to operate. About mid-way thru this process, just befre and continueing after the T-stat opens I periodicaly raise the rpms and carefully punch the throttle a few times to increase flow speed and volme to help with the air transfer towards the front. While I'm doing the fiddling with the throttle and pacing/circling around checking & inspecting I'm bleeding any new accumulated air from the bleed screw multiples of times. I'd guess my normal procedure takes 20-30 minutes at least . Once everything has been throughly checked and all systems inspected for proper operation & temp I finally shut off engine, check level in the tank and replace the cap. Then a short road test of a mile or so varying speed/rpm conditions and back, park, shut down and perform the last water level/idle speed/running condition check and one last air bleed check. If everything checks out = done.


By performing this thourough procedure a cooling system can usually go several months before needing further attention/bleeding.

A timely note for those who are seeing weather changes. At this time of year as the heater valves are turned back on for the first time in many months it is quite common to dump a large amount of air into the system that has accumulated over the summer in the heater cores. This large air pocket trapped for months in the heater cores gets displaced by water and can cause a serious temp rise during the days .

Your Mileage May Vary.

Regards, JRV

>>-30% Honda anti-freeze (no silicates/borates) with WaterWetter <<

excellent tip btw.

Regards, JRV

JRV,
It seems that our procedures are resonably similar...with one exception. I gave up on the "punch the throttle" routine, as the coolant just spurts from the overflow tank all over the engine, when the throttle is released.

I'll just be a more patient in this process...as nothing could be a bigger PITA than the Lotus Eurpoa I once had...HA!

As always...I appreciate your input.


Regards,
David

>>I gave up on the "punch the throttle" routine, as the coolant just spurts from the overflow tank all over the engine, when the throttle is released. <<

Uhhhh...yea that can happen {}

I should qualify revving...small revs to 3K-4K rpms basically to increase flow through the heads and T-Stat to dislodge any potentialy trapped air. Of course it's possible this may be unecesary, and just a function of my trying to leave no stone unturned in getting those pesky air pockets removed.

I might add that Boxers and 328's are especially difficult to completely purge because the radiators don't stand striaght up and the radiator incline seems to cause a little more difficulty?

Best Guys, JRV

When I bled my 328 I made bleeder screws with 3' long hoses that allowed me to bled alot of coolant out (and pour it back into the tank) while the car was running.
I think brake bleeder screws could be purchased that will fit.

>>I think brake bleeder screws could be purchased that will fit.<<

Hi Mark, welcome aboard.

The hose idea you mention does work well and insures a thoirough bleeding. As for the Br. Bleeder screws, the 348's/TR's and later cars with the radiators in the back use just that, unlike the raduator mounted bleeders though, the taps have a machined seat that the bleeder screw tightens against, while the radiators simply have an open hole..

Regards, JRV