help with coolant leak/ overheating 79' 308

Proper level is 6cm below the filler neck.

I would suspect a sticky thermostat or plugged radiator. You can ask Carlo more about this, but seems most 3x8's require at some point in their life, to have the radiator removed, the bottom cut off and a brush run up through all the tubes to remove all the accumlated crap...kind of like getting a catheterization done on your heart.
I think Carlo called it having the radiator "rodded out".

 

Sounds like you had some air collecting in the radiator. Any air in there will seriously impact coolant flow, resulting in overheating and loss of coolant via the overflow from the expansion tank.

Question is how the air got there. Normal way is for the water pump to suck air via the upper hose to the expansion tank and send it downstream to the radiator. Abnormal way is a blown head gasket or cracked cylinder liner or cracked head.

First thing to do is bleed any air from the radiator via the bleed screw and bleed any air from the thermostat housing using its bleed bolt. Second thing is to plug the upper hose to the expansion tank (i.e., the 3/8" ID hose) using a short section of 3/8" solid bar stock inserted in the hose.

I had the same problem with my '78 308GTS. Plugging the upper hose fixed it. I never have to bleed air out of the system now (for the past eight years or so, anyway).

Of course, you could have one of the more serious problems, but I'd try the above first.

Bob
'78 308GTS
'01 Corvette Z06

 

LOL, it's more like getting a hardware enema from the proctologist.

 

Hello,
Sorry to hear of your overheating problem , the bleed valves are located on the top of the radiator and on some later 308/328 the thermstat housing.May I suggest you read tnowak's post and add your name to his list of owners looking for a simple but very effective solution to bleeding problems,you will not regret it.
Regards,Tom.

 

Get new radiator cap, these things get old and lose its presure resistant. You can allso place thin rubber "washer" under radiator cap.
You loose your coolant as you drive and expansion tank spits out coolant as radiator cap don't hold presure.
I have four Ferraris two 308's and two Mondial Cab's (30k and 40K kilometers) and all have new radiator cap because old one don't hold presure.

 

I would suspect nothing more serious than a bad expansion tank cap that needs replacing. The spring has gone weak & you've been dropping coolant while driving till you reached the point where the level dropped so far that things started to get a bit warm. So low in fact that the surging up & down on the temperature gauge relates to when the water pump managed to get some water up to the top of the motor (the temperature falls) and when its dry (the temperature rises) - not forgetting that the temp sensor is right there at the top of the block.

Because its run so low you've probably got airlocks around the place which is why it started chucking water out when you filled it. Fill it again & run it for a while & keep bleeding the rad & the top of the T'stat housing.

Once you think you've got most/all of the air out let it sit there idling & watch the temperature. You'll know if I'm right if water coolant starts dropping out the overflow.

If it does need replacing you need a 1.1 bar cap.

 

all good points.... also check to see if cooling fans are kikin in.................

 

I've been experiencing exactly the same problem, and I've burped the system several times, and I replaced the coolant tank cap. Nothing seems to make a difference!!

This is the first time I've heard anybody talk about plugging the upper (i.e., 3/8) hose to the coolant tank. Are there any possible problems associated with doing this? I mean, if plugging it resolves the problem (and it's a problem that many of us seem to have!), why did Ferrari put it there in the first place?

What purpose does the upper hose serve anyway?

Thanks.

 

The upper hose returns coolant from the engine to the tank, ie: allows for expansion.

The tank's upper hose fitting has a tube on the inside that extends down below the tank's coolant level. This is so that when the system cools down, it will suck coolant back into the motor & not air.

The specificied coolant level in the tank is to ensure the tube's end is below the coolant level. If the coolant gets low, air will get sucked back into the system.

It's fairly common for the upper hose tube to corrode inside the tank & develop an air leak, or even break off inside the tank, thus letting air get sucked back into the engine.

I believe that the 'plug the upper hose' workaround is a test to determine if air is getting into the system via the upper hose than it is a 'fix'. If plugging works, then the problem is likely the tube inside the tank. A good radiator shop should be able to open up the tank & replace the tube.

An alternative to plugging the tube would be to add an in-line check valve that would let coolant flow thru the tube into the tank, but would block anything from being sucked back into the engine thru the tube.

Just did a quick search & here's the TNowak post:
http://www.ferrarichat.com/forum/showthread.php?t=203216

 

I just checked, and neither my original coolant tank nor my NOS coolant tank have a tube inside that runs from the upper connection down below the coolant level. My car's a 1977 and uses the 'vertical' tank as opposed to the 'horizontal' one that I've seen on other model years.

Verell, is it possible that the older 'vertical' tanks don't have this internal tube?

 

I haven't looked at a carb'd cars vertical tank, so it's certainly possible. In that case, I don't know what prevents sucking air. Any chance there's a check valve somewhere in that upper line that has gotten stuck open?

 

Nope. It's a straight coolant tube from the top of the tank to the thermostat housing. Funny that this hasn't come up as an issue in the past given the number of coolant-related posts on fchat. So, it would seem that installation of a check valve might be in order, although, if a check valve is put in-line, how's coolant going to be drawn back into the engine as it cools down?

I wonder if we've opened up a new can of worms!!

 

I believe this is a problem specific to the carbed 308s (i.e., vertical tank models). I ran mine for a couple of years with the upper tube plugged. No effect I could see, other than I no longer had to bleed the radiator every day, or watch the coolant flowing out of the overflow when I stopped, or check my mirror regularly for steam coming out of the engine hatch vents. Solved the problem. Finally decided to have a radiator shop extend the tube down inside the tank to a level below the coolant. Same result. Either way, I never have to bleed any air out of the radiator.

Later, I also replaced the heavy, flat-fin industrial radiator core with a standard crinkle-fin automotive core and replaced the worthless radiator fans with modern 13 inch pancake fans. Large increase in cooling capacity. Never have any cooling problems. Fans rarely come on, and, when they do, the temp goes right down.

Bob
'78 308GTS
'01 Corvette Z06

 

WRTO the purpose of the upper tube.....

I believe it is intended to equalize temperature between the coolant in the engine and the coolant in the tank. Not clear why this is necessary, but this is an Italian car. Perhaps it is to ensure that any person opening the radiator cap improperly will be doused with hot coolant rather than the cool variety.

At any rate, the water pump (in addition to circulating coolant through the engine) is supposed to provide a small flow of coolant out of the tank via the large lower hose and return coolant to the tank via the small upper hose. Problem arises when (for some reason) the flow is reversed, and air is sucked out of the tank via the upper hose, then forced downstream to the radiator, where it collects. Any air in the radiator seriously impacts coolant flow, resulting in overheating, which causes coolant to flow out of the overflow tube. And then more overheating. Vicious cycle.

On carbed 308s, if air collects in the radiator, plug the upper hose (or modify the tank) first. That should fix the problem. If it doesn't you've got something serously wrong. If there is overheating, but no air in the radiator, then you probably have a problem with the thermostat or the radiator.

 

oh, by the way:
NOTE; Remember to mesure the old radiator cap, so the new one has same, or longer distanse of spring that presures the expansion tank. If you have boght too compact cap it does not hold presure any better then old one, almost all new aftermarket caps don't work in Ferraris. Load of spring holds the presure if it reaches expansion tank, if not you can make extra seal under the cap.

 

I'm going to stick with reccomending inserting a check valve in the upper hose. It's closer to the OEM design than just plugging the upper line. A check valve will permit warm water to circulate into the tank, allow expansion water to enter the tank, and prevent sucking air back thru the upper hose.

The lower hose will provide water to the system when it cools & needs to draw from the reservoir.

Altho, I don't see how plugging the line would cause a problem, but haven't spent a lot of time on this part of the system.

 

Verell and I have been discussing this off-line. Thanks to Verell's terrific help (as ever) I have ordered the following part numbers from www.mcmaster.com

1 x 47715K21 (bronze check valve)
2 x 5670K83 (stainless barbed tube fitting ... no, they can't supply the required size in bronze)

Once I've received and installed the parts, I'll take a couple of photos and report back on fchat.

Hopefully this will solve many of the cooling problems associated with older 308s that use the vertical style of coolant tank.

 

Sorry, I posted slightly incorrect part numbers earlier on. If this little experiment works, you'll need the following:

1 x 47715K22 (bronze check valve)
2 x 5670K83 (stainless barbed tube fitting)

 

I'm assuming the GT4's all have the "horizontal" tank...but would they also have the tube extending into the tank? Seems I need to bleed the radiator quite often....