328 coolant level on expansion tank...

The tank should be half full, right? 6 weeks ago, I drained some fluid close to the halfway mark as the amount of fluid has expanded (engine was cold when I removed the cap). Yesterday, 8 hours after driving, the coolant level has "expanded" and is almost full again. No coolant leak under the car.

Car runs fine. Temp gauge reads fine when car is running. Car had major service July '06.

Should I siphon more coolant out of the expansion tank again?

Thnx.

 

You better drain the system from the front bleeder first...
Ciao
Eugenio

 

Can you explain why (I am not really technically inclined; I only do very minor works on my car)? Thnx.

 

I just know that some air forms into the system. From where, do not ask me .
The suggestion simply comes from experience. My car has this "problem" since I bought it. Every now and then I simply loosen (with the engine warm just after a normal drive) the bleeding screw on the top, right side of the radiator and let the air go out. Every time there is some air. I suppose that you will find a lot of it the first time you do it.
Ciao
Eugenio

 

Ron,

Ensure that the heater valves are open (heaters on) when you bleed the system. Do a search on how to bleed the system, it is quite staight forward.

Good Luck

 

Yep, it sounds like there might have been some air in the heater cores. Once the heaters came on, the air started circulating in the system.

When the air heats in the lines, it expands, and can push coolent out to the expansion tank.

You might also notice the coolent temp gauge varying a bit. When an air bubble passes the sensor, the temp reading goes up, and then back down after the air passes.

Always bleed with the heater cores wide open (all the red bars lit on the heater controls).
It's amazing how many shops miss this - even in january.

 

Air expands to a greater volume that water when hot. The coolant lines are below the thermostat housing and the coolant reservoir in the rear and most of the radiator in the front. It is normal that if, in a fully and properly bled cooling system, the coolant level drops below the middle seam of the reservoir, that that is an indication that the system is not full of fluid and that air exists somewhere in the system.

If there is a volume of air trapped in the system, it prevents circulation and causes large changes in system volume, like what you are seeing and most pointedly, by a discharge from the reservoir overflow tube after a drive.

The fluctuations on the temp gauge reflect the progress of the circulation. If it's high, it's because the thermostat hasn't opened allowing cooler water from the rest of the system volume (all the water in the lines and the radiator) to be included in the volume of cooling water being measured.

It fluctuates also due to the "bubbles" (or more properly "embolism") of air working their way around the engine and cooling system. The water temp gauge sender cannot measure gas (or air) temperature, only liquid. That's why when the gauge climbs quickly, it's due to hot water coming into sudden contact with the sender. That's also why there is a bleed screw on top of the thermostat, which a lot of shops and more individuals miss...

The directions in the owners manual are good enough for periodic bleeding. If a cap goes bad and coolant is expelled, the system volume will decrease and air will be aspirated when the engine cools down. That is often why people continually and frequently get air every time they open the bleeder in the front of the car. It also helps to raise slightly the front end of the car, bleed the radiator, then raise the rear of the car very slightly, bleed the thermostat housing and top off the reservoir, all while having the heater on full blast.

It doesn't bleed fully until the thermostat opens, which is why this job can be messy! <grin>

-Peter (first job I learned how to do on these cars...)

 

If you bleed it cold, you won't burn your hand.

 

When bleeding, does the engine have to be idling? Or do I do it say, 15 minutes, after the car is driven?


Okay, the heater valves should be open when bleeding. Is this while the engine is running or not?

Thank you, all.

Ron

 

I always do it while the engine is idling. Doesn't work easily if you don't. Under no circumstances bleed while it's hot and after you shut it off, otherwise temporary rise in system pressure due to heat soak can make it very messy. <grin>

Yes, heater valves open at all times, especially through the warm-up phase and past the point where the thermostat opens (by the time the fans kick on.)

 

You might have to do the above sugestion of bleeding the system 4 to 5 times to ensure all the air are escape. This is what I did to my 85 308 QV and I left the coolant in the expansion tank just a tad above half way. don't forget to turn the heater on to max. Since I did all this I never had anymore overheating problem, Everything has been normal.

 

Thanks guys. I tried it. And it worked!

Turned on engine, heater valve on (all red), and when the radiator fan kicked in, I slowly unscrewed the front bleeder and stopped when I felt some coolant come out. Now (2 hrs. later), the coolant level is just about the middle seam.

I guess I'll just repeat the process as needed, as suggested above.

THANKS A LOT!!

Ron

 

I'm pleased that we were able to assist you.




.

 

Rough numbers:
IIRC water expands about 4.5% from freezing to boiling (4C-98C). Knock off a bit for starting at room temp and figure a system with 4 gallons of water, expansion would represents about a quart. (the slide rule generation was encouraged to do rough numbers in the head to establish the decimal location)

You might add a quart to the expansion tank to confirm what you experienced to begin this exercise ... or you might just not care. In any case you provided and excuse to bring out the bleeder procedure pros&cons. Then again, if your car is continually producing water out of nowhere we could have the start of a mobile hydrogen fuel cell.

 

My 328 does this too. Right now its stone cold & I know that if I went to open the expansion tank it would be full to the brim and I'd see coolant coming out because the system seems to be permanently pressurised. Alternatively I could bleed a load of air out the radiator first and once I'd done that the level in the tank would then be spot on correct. I've probably bled enough air out my radiator in the last 18 months to fill a house so it can't be just residual air from the heater core (or similar).

Its as if the air that should be (was) in the tank is getting pushed through the system where it then ends up in the radiator. The expansion tank then ends up being full to the brim. The extra (residual) pressure in the system makes me think that its also actually sucking in some air somewhere when its running. I think it could only be doing that at a point where there might be negative pressure in the system - i.e. maybe just in front of the water pump(?) - but who knows.

I dunno - its all theory! All I know is that its been doing this for about 18 months since I drained the cooling system, replaced the T'stat and replaced the expansion tank cap.

Something's not quite right somewhere but I've no idea where. On the positive side the thing runs at a rock solid stable temperature and hasn't dropped an ounce of coolant (i.e. I havn''t needed to add any) in 18 months. My heaters also both work perfectly.

If I bleed the air out my radiator when the system is cold then the level in the expansion tank will be exactly correct. I've also pressure tested the system & it'll hold 15psi till the cows come home.

All in all, I've just stopped worrying about it!

I.

 

Have you bled the thermostat housing?

 

BTW, the proper level in the expansion tank should be 6cm from the top of the filler neck. I measure from where the cap seals against the inside of the neck. Is that right?

 

I've owned the car for over 4 years and this never happened until about 2 months ago. (major service done July '06). My ignorance led me to siphon coolant out of the expansion tank. Then I noticed the level has gone up again. Thanks to our friends here at Fchat... I followed their recommendations and solved the problem on first attempt!

Peter, I haven't touched the thermostat bleeder to date.

Dave, am not sure about 6cm, but the manual (and I remember Sean Harris
at Steve Harris Imports told me) says the correct level is just about the middle seam of the reservoir.

Rgds,
Ron

 

On my manual (euro 1986 GTS) it says 6 cm from the top of the filler level.
Ciao
Eugenio
Image Unavailable, Please Login

 

I have a similar problem with my 328 blowing out coolant. I suspect it is combustion gas as it smells of exhaust when I remove the coolant filler cap and is still pressurised, even weeks after use. It is worse the harder the car is used, the problem first appearing at a track day. Another thread here mentions the fact that re torquing the heads is stipulated in the service schedule but rarely done. I am considering having the coolant tested for gas and the head torque checked at the next shim service.
Gnasher

 

I just had the test done, 20 quid at a classic car garage just down the road (Ferrari dealer told me it should not cost more than @ £85 with a discount).
Stuck a tube of coloured liquid in the filler, it bubbled away like a '70s novelty lamp, then the liquid changed colour - double proof.
I reckon that if the level in the tank is kept about half as is sugested, the gas just blows out taking very little coolant with it. From the amount of posts with similar symptoms it would seem 328 head gasket failure is not as rare as believed.

 

I believe it can be avoided if the heads are retorqued at each major service.