308 QV: air in the radiator.

have you bled the system and refilled? you may be sucking air in the expansion tank... I jacked the back end up opened the blead valve on the radiator, and filled the tank with a hose... kept the water going till a steady stream came out of the bleed valve... then shut that off... moved to the thermostat... left the tank full.. and let the system bleed out what was not needed.... this procedure worked very well for me... as for the other way you could be getting air in the system - your radiator... has it been inspected? mine was rotted out... so tons of pin hole leaks, that still alowed ok cooling, but sucked air into the system when it cooled off at night... over time this just builds up....

Bleeding air is a painfull job... my experienice is that you only get air in the system if you have a part failing... thermostat, pump, or radiator... or cap..

best of luck!

 

I have a similar sounding issue on my 328. I bleed the air out the radiator at which point the level in the tank is where it should be (6cm below the neck). Go for a drive & then let the car cool right down - there will be air in the radiator & the tank will be absolutely full. Bleed the air out the radiator & repeat ad infinitum.

I've been round & tightened everything up I can find (hose clips etc) & I've pressure tested the system which revealed very little. This has been going on since last year when I drained my cooling system & refilled it & also replaced the Thermostat.

I've no idea what the cause is to be honest. Next step is probably to get the coolant tested for hydrocarbons I suppose to find out whether its some kind of head gasket leak.

I.

 

Iain, have you tried the old trick of raising the front of the car up when you bleed the rad?

 

No I havn't but I don't think it will make any diifference. This has been going on for months - I must have bled the rad 20-30 times & probably taken enough air out the system to fill the entire system twice over! I don't believe I am dealing with just having trapped air from when I refilled the system.

One of two things is happening. Either

a) The Air in the expansion tank is somehow being sucked through the system & ending up in the radiator leading to an expansion tank that's full to the brim and a radiator with air in it.

or

b) Air is being drawn into the system somewhere that is then getting caught in the radiator whilst at the same time the air that is in the expansion tank is being forced out the overflow (hence why the expansion tank is always full to the brim & the radiator has air in it after the car has been run).

For clarification I have a new Ferrari cap on the tank & also in all the time its been doing this I have not needed to add one drop of coolant. Car runs at perfect and stable operating temperature of about 175 (second mark on the gauge). Temp climbs to 190 & the fans come on in in traffic as expected at which point the temp drops back to 175.

After coolong down & once the air is bled out the radiator the level in the tank is exactly where it should be & where it started i.e. I am not losing any coolant.

One thing I am going to try is to buy a cheapo 1.1 bar generic rad cap from somewhere & see what happens if I put that on the thing.

A third option is of course that "they all do that" !! But somehow I doubt it.


I.

 

My '79 308GT4 does the exact same thing... I don't know what the problem is, either. I just replaced my expansion tank cap with one made by Stant. We'll see if it helps.

 

I don't believe that you can get all the air out and never have to bleed the rediator ever again. I think the 308 manual suggests bleeding at the radiator on a regular basis. I do.

 

I had better luck with a cheapo Stant radiator cap on my old '85 308 than a new Ferrari cap.

Bleeding with the front end elevated is a better way to do it as the air rises to the highest point in the system.

Another thing to check is if you have any tiny pinholes rotted through the top of the expansion tank. This is not uncomon and can be a cause of air getting sucked into the system

 

Some common issues on cooling systems is a loose cap on the expansion tank, and a leaky bleed valve on the radiator. Sometimes the bleed valve doesn't want to close tight, especially when hot.

Another frustrating source of air in the system is the heaters. On the 308/328 the heater controls actually cut off coolent flow to the heater cores. If you bleed the cooling system with the heaters off (as in summer) you can still have air leaking from the heater cores into the cooling system. It's amazing how many shops forget to bleed the heater cores with the rest of the system.

The best way I've found to get all the air out of my 328 is to turn the heater cores to full hot and then turn the ignition off. With the car cold and not running, I top off the expansion tank and apply pressure to the expansion tank cap (hand pump) and then bleed at the radiator and thermostat until I get a steady flow of coolent. That generally gets it all. Readjust expansion tank level and happy motoring. (Oh yes, turn the heaters off again before driving in August. )

 

Franco,

I've been chasing the same problem on my 78 GTS for quite some time. I have to bleed the radiator every 2 or 3 heat cycles. If I don't, the upper header tank on the radiator fills with air and the coolant backs up into the expansion tank. eventually coolant will come out of the overflow tube. The coolant temperature is normal.

I replaced the radiator, the expansion tank cap, and the thermostat about a year ago. All the coolant hoses were replaced about about 2 years ago.

I recently checked the coolant for evidence of CO2 (combustion gas) and there was none present. The SnapOn tester I used easily detects CO2 from my breath, so it is working properly. This means there is no combustion gas leak into the cooling system.

I recently went back to an old Stant 16 psi pressure cap and this helped a little. With the cap I took off, I had break the seal before I could bleed the radiator. With the Stant cap, I no longer have to do this as the bleed back valve works properly.

I thought of providing a bleed line from the radiator bleed valve to the header tank, but I'm not sure this would work as it would have to be routed low through the sills and would collect water. I've thought about whether there is enough pressure differential do to the high water in the expansion tank to allow air in the radiator to purge water in the bleed back line and allow the air to return to the expansion tank from the upper radiator header. I simply don't know the answer to this and it would require some special fittings to try. In the end I think it's better to discover the reason why air collects in the radiator and fix it properly.

My next step, when I get the motivation, is to again check or replace the thermostat. The one thing I'm not sure about is whether the thermostat I fitted has an air bleed hole in it and if it does, what it's orientation is. I believe the hole, if present, must be oriented to the 12 o-clock position. Presumably, this would allow air in the system to bleed back to the expansion tank so that the coolant will occupy the normal coolant volume, especially the upper radiator header. I'll have to check the shop manual to see if there is any reference to a bleed hole in the thermostat. If I replace the thermostat, I will try a factory one as there may be features on it to address this problem.

This problem appears to be more common than I thought, but it must have an answer.

Bill

 

So why do you think there's a problem???

You say everything is normal; coolant temp. etc.

Coolant coming from the overflow tube may be because the system was slightly overfilled. If so, it will eventually come to the right level on its own.

It doesn't sound to me like you have a problem!

 

Sounds identical to my 328. I havn't seen what happens if I just leave the thing because I keep bleeding the air out. Maybe I need to try that - but so far I am not losing any coolant. My T'stat is not a Ferrari original (its a pattern part I got from Daniel at Ricambi) & didn't have a hole - so I drilled one in it to match the original & then set it in with the hole at 12 O'clock. So I'm pretty sure that's not the cause of the problem.

If air is being drawn in then I suppose it must be at a point of negative pressure in the system otherwise air wouldn't be going in, water would be pouring out! I just can't quite get my head around where such points in the system might be! Any bright ideas gratefully received

I.

 

Sounds like the tube from the radiator to the expansion tank is drawing air in somewhere as the system cools. If the system is working properly, as the system cools and the coolant volume contracts a slight vacuum will be created that pulls coolant back into the radiator from the expansion tank. Any small air leak anywhere between the top surface of the coolant in the radiator and the top surface of the coolant in the expansion tank will cause air rather than coolant to be drawn back into the radiator as it cools. Is the draw tube inside the expansion tank okay? It draws the coolant from the bottom of the expansion tank just like a drinking straw and any leak as I stated above will cause it to not function. Also the expansion tank must be vented to atmosphere as it is atmospheric pressure acting on the top surface of the coolant in the expansion tank that actually pushes the coolant up the draw tube and back into the radiator. Be sure and check the radiator cap. There should be two seals on it. The purpose of the upper one is to make the air tight seal that facilitates the formation of the vacuum that is required for the expansion tank system to function.

 

I'm not sure how much of this applies to the way the system on the 3x8 is installed.

The expansion tank on my 328 has 2 connections to it - a flow & a return by the look of it. The flow side is the larger and lower connection spigot. There's nothing fancy inside its just a connection at the bottom of the tank.

The tank is T'd off the return side of the coolant pipework i.e. the main pipe that comes back to the engine from the radiator. Bear in mind that the engine & expansion tank are at the back of the car while the radiator is down the front!

The other connection to the expansion tank is made to a spigot that enters the tank towards the top. Coolant appears to enter the tank via this connection from a hose that is connected somewhere in the V of the engine.

Have a look at http://www.eurospares.co.uk/partTable.asp?M=1&Mo=421&A=1&B=23049&S= for a diagram of the system

 

You're right, the generic system I described is different from the system in the diagram in your link. The coolant in that system appears to return from the expansion tank by gravity. The breather pipe #42 in the diagram is the only connection to the system that isn't submerged at all times (it's end connected to the tank is above the coolant level in the tank). If the rest of the system is air and water tight, that tank end of breather pipe #42 is about the only place air could enter. I'll look at the system on my X1/9, as it is very similar, and see if I can figure something out from it.

 

I think you gents might be onto something here. If the expansion tank is not full of coolant (which it shouldn't be if it's filled to the proper level) the top hose will allow air to be drawn into the system as it cools.

I've had the same problem on my '78 308 and just considered it a "quirk" that I had to live with.

Could it solve our problem if there were a pick up tube attached to the top hose that went to the bottom of the tank? Shouldn't be that hard to fab up some kind of adapter that would hold a hose in the tank and still hook the outside hose to the pump.

I can't see where it would hurt to try it anyway. Or is there something that I'm not seeing right?

 

Same, same...... although I'll get air out the thing hot or cold. What you've described Franco is a bit more confusing because you seem to be saying that if you let the thing cool down then the radiator is now full.

 

I sort of see what you are saying - but, as above, I'll have a ton of air in my radiator straight after switch off so I don't think the problem is occuring during cool down - its drawing in/moving air whicle its running.

I.

 

How about looking at this old school style.
Years ago on the workshop floor we would have filled the expantion tank, left the cap off and started the engine.
If bubbles started to gurgle you had a head gasket problem! That is the only thing that can produce air into the system.
It has no place to vent, I am sure if you left it, it would over pressure and blow at a weak point. for example rad or hose.

Be ready to pop the cap back on a bit quick because when the stat opens coolant will woosh out like a fountain.
You may find its only after the car is up to running temp that it leaks, after the alloy of the engine has expanded.
If this problem was not happening before it will only get worse.

Be warned the coolant gets very hot! very quick, you should see bubbles almost straight away. If so stop and get a specialist!!!!

Once again be carefull



Mark..

 

If the problem was a leaking head gasket would you not see exhaust/gas residue in the coolant especially if you drained some into a clear glass?

 

Hmm,
This sounds familiar, there was a thread a few years back about this problem.

I just don't remember the specifics very well. I believe it turned out that something inside the coolant tank had given way. Possibly an internal tube from that upper fitting that was supposed to stay submerged had come off???

BTW, there are test kits for exhaust gasses in coolant, check with a good commercial auto/truck parts place, probly not something a consumer one like AutoZone, Pep Boys, etc would have.

 

Verell,

SnapOn made the one I borrowed from a kindly local mechanic. It worked great in that it positively detected CO2 from my breath into a cup. CO2 is heavier than air. There may be others available.

Bill