308 expansion tank

My 81 308 needs a new expansion tank. The original has been welded up several times and I don't think there is enough metal left on the top side to make it worthwhile to try again. I have located a new one at Superformance, for a very good price, plus it's made of aluminum that should last way better than the OEM one. Very nice looking piece. The only problem is, it only has a fitting for one thermal switch and my car has two. I'm away from home and don't have my service manuals with me so I'm not exactly sure what they control although I suspect it is emissions related. My question for the experts is - can I use a single switch in place of the two - do they activate at the same temperature?

Thanks

 

I just got back and had an opportunity to look at my car, the second thermal switch is a vacuum switch that controls the EGR system. As my car has no cats, the air injection pump and lines have been removed and plugged - my question now is, at this point, is there any reason not to cap off the EGR plumbing. Is there anything I need to look out for?

Thanks

 

The EGR system is a system onto itself and does not interact with any other system on the engine. This should apply to your car as well, but the following overview statement is from the FNA Mondial Dealer Introduction book (print# 90000-3548 8/81):

"With the Ferrari emission control system, the NOx emissions are principally reduced by the three-way catalytic converters.

The Exhaust Gas Recirculation (EGR) system introduces a small flow of exhaust gas into the intake manifold. This reduces the NOx emissions before the catalytic converters specially during light accelerations, when the catalytic converters efficiency is low because the exhaust gases temperatures are low."

 

I've had a question on the top 3/8" hose on the 308 cab car tank. It goes from the top of the tank to the thermostat housing. Why is it there and what does it do. Just curious

 

Any air in the system will go to the thermostat housing being the high point. That hose returns it to the expansion tank where it belongs.

 

Thanks

 

Is the thermostat housing air bleed redundant then?
Is the tank end submerged or not?

Just not totally clear on how its supposed to function.
Thanks for any explanation.

 

No. Bleeding is done at the time of initial fill. If rebleeding is ever required something in the system is faulty.

Yes. But there needs to be air in the system to allow for the thermal expansion of the water. Air will always migrate somewhat and is no problem as long as it does not congregate in sufficient quantity in any place where it will prevent proper function of the system. One of those places is at the thermostat.

Air goes up hill.

 

Thanks for that.

Get that gas is a liquid and the denser forms flow lower in our gravity well.

Have been confused by how high in the expansion tank that hose connects. Some of the odd ball or ball valve ideas for it postulated in other threads here haven't helped my clarity.

 

Why would anyone want to put a valve on it?

 

They wanted to -
a, Blank it off.
b, Put a one way valve in.

It was a thread a month or so back with a general confusion about that design. Several thought they knew better than Ferrari.
I had my doubts about that but no first hand experience.

 

Wonderful thing the internet. Any idiot with a keyboard can be an expert and hand out all sorts of bad advice.

 

Wish my 328 did that! I still perpetually find air in the radiator & I just changed all the main cooling hose links and the water pump. Ran a block tester on it & no sign of combustion gas in the coolant either so Lord alone knows where its coming from - darn thing has been doing it for the last 3 years!

Doesn't lose any coolant either, the air from air gap in the expansion tank just seems to get moved around the system & end up in the radiator sometimes (and the tank ends up full)!

 

If it is not overheating leave it alone. Who cares if there is a little air in the radiator.

If it was properly filled and has a good (NOT OE......GOD FORBID) cap it cannot have more the the equivalent of about 3 quarts of air in the system.

If it does you have done something wrong.
If it is gaining air you have done something wrong.
If it needs constant bleeding you have done something wrong.


We probably service 50 308/328 here and I know of none of them that gets bled more than once every 2 years when we change coolant. They all work exactly the same. Yours is no different unless something is wrong.

 

+1 on what Brian said. I owned a 308 and 328 and they will invariably always have some air in the system, when you bleed them. Car never overheated, so why worry about it. Brian what cap do you recommend? I believe I had the four eared oem version on both my cars with no issues.

 

I doubt the air is getting moved around from the tank to the radiator. Usual cause is old dry coolant hoses allowing air to get in as the engine cools down and pulls a vacuum on the system. Signs of seapage, not really a dripping leak yet, will often be the source where air gets in. Pressure testing a system dry with air only will show numerous leaks that fluids will seal up.

 

Either that or he is bleeding and topping up, bleeding and topping up, bleeding and topping up. Some air from the required air space WILL get to the radiator top tank and he is just perpetuating a cycle that will never end.

In either event, inspect, repair, fill, and bleed the system and just leave it alone to do its job.

 

Good point

 

Its pretty much all I've done. Never needed to top the thing up, it just seems that some of the air from the expansion tank gets moved around the system & collects in the radiator. It has also been known that a couple of days after I've run the car if I take the cap off there is actually still pressure in the system. That one is most odd. Not sure if its still doing this since I changed the hoses & the WP though.

There have also been times when the expansion tank has been completely full. Bleed the radiator though & the level returns to normal. Its not pulling this trick so much these days though.

The thing runs at a perfectly stable temperature at around the second mark on the gauge whatever the weather. So the T'stat is good & heaters also work fine, so no air in there either I would think. I do have a genuine 1.1 bar cap though (which is only a year or so old) - maybe I need to find another one?!