328 Cooling system issue...It all becomes clear to me now...

Mike,

I am NOT a competent mechanic, not even a mechanic. BUT I have been told time and again that the first thing to do BEFORE having the car serviced is to fully open the heating system for about thirty miles; and leave it open. Then, AFTER having the car serviced, when collecting it, immediately open it again (if it has been closed) for thirty miles and check. The heating system on the 3x8 is the worst air trap there could be; as such, it should be regularly operated, just as the windows.
Rgds

 

My own cooling system saga that has been going on for about six months is chronicled in my "Air in the cooling system" thread. For me it began with little signs, temperature creeping up a bit when stopped in traffic and cooling fans not cycling off once on until I started moving again. I did a complete drain and refill of the system following the Birdman and Verell bleeding procedures and it was okay for awhile but eventually would start spitting or dribbling coolant out the overflow and acting up again. Other symptoms were weird swings of the gauge needle, it would rise above the 195 mark after only 5 minutes then suddenly swing back down below 140. In cruise it would barely rise above the 140 mark. I replaced the cap, the thermostat, the radiator, the water pump and every hose and got it working perfectly. Temperature would rise steadily to under the 195 mark and stay there. At idle it would rise slightly above the fans would kick on and after one minute it would have dropped and fans cycled off.

But after every test drive I could bleed more air out of the system at the radiator and on an extended drive it would eventually begin to act up again. I had done multiple block tests with negative results for combustion gasses in the coolant but if I started it up with the cap off I could look in the tank and see air bubbles coming in through the bleed/recirc line from the engine. So I did compression and leak-down tests and found that I could hear air bubbling into the coolant when I had 100 psi on #4 cylinder. Also found #4 to be the lowest in cranking compression at 155.

So that's where I stand at this point and I'd suggest a very easy test is to just start the engine cold with the cap off and watch the stream into the tank with a flashlight. If you continue to see air bubbles after a minute or so there's something going on. If not you are okay.

One thing I'd add is that the tales about bleeding the air out of these systems are true. I measured how much I drained out of the system, including the block, when I did the water pump and it was about 4 1/2 gallons. When I refilled I had only put in a bit over 3 gallons when coolant was flowing out of both the radiator and thermostat bleeds. That was with heater cores wide open. It took several test drives and bleeding the radiator after each before I had put in the right amount of coolant. The system takes 18 liters (4 3/4 gallons) according to the book. Bear in mind I had every hose and tube off so my system was about as empty as you can get it but whenever renewing your coolant it's a good idea to drain it into a 5 gallon bucket so you know exactly how much you took out.

 

Then you should be okay. Air in the system causes the symptoms and once you get it all out it will work perfectly fine. It may take some effort to get all of it out but eventually you will succeed. Whatever is in there seems to end up getting trapped in the radiator so if you bleed that out after every drive for a few days you should get all of it.

 

I'm fighting the same issue on my car. It first started a while after I replaced a lot of the coolant hoses (not immediately). I like to think that when something stops working correctly, go back to the last thing you touched. For me, that would be the coolant hoses, so that would make sense. I currently have the car down for timing belts, so I ran a compression and leak down test this past weekend. Nothing jumped out at me. 175-180 psi on all cylinders and 5-8% leak down. All of this is on a cold engine.

What I did find when starting the timing belt project was that I had a couple of leaks at hose clamps when I pressure tested the coolant system. I fixed those prior to draining the coolant for the belts. The plan is to put the car back together and redo the leak down test with coolant in the car and look for bubbles. A friend also suggested pressurizing the coolant for an extended time and look in the cylinders with a borescope for coolant. However, the more I think about this idea, I'm not sure if it will show anything. The coolant system would only be tested at around 15 psi compared to the 180 psi that would be introducing air into the system.

I am also going to replace the radiator cap with a new one. I already did this when the spitting coolant started, but they are cheap so I got another new one.

I am hoping that between the new cap and fixing the leaking hoses that the issue will magically go away. I still think it could be a head gasket, but with good compression and leak down results and with coolant and oil that looks normal, I am hoping for the best.

 

And test the cap itself (but even doing that doesn't measure what the pressure is inside the cooling system when it's spitting - i.e., the tester can seal to both the filler neck and cap well, but that doesn't guarantee that the cap seals the same to the filler neck). Completely agree that is not typical "328 when new" so look forward to your findings.

 

Are you also "spitting" coolant at the overflow hose on the filler neck, or is your coolant loss more mysterious?

 

My suggestion is to first of all continue doing short drives and bleeding the air out of the radiator after each one until you are absolutely certain that you have put in the correct amount of coolant - the system takes 18 liters, which is 4 3/4 gallons. You have to account also for any that gets spat out but I found that if I did a short 10 mile loop that included some WOT runs onto the freeway I could get back into the garage before it started spitting and bleed the air out of the radiator immediately. You should have one of the drilled bleeder bolts from either Verell or Superformance to make it easier. Keep the heater temp valves wide open, you can keep the vent valves closed. I don't think you need to worry much about the thermostat bleeder except on initial filling because when starting cold the thermostat is closed so coolant is only circulating through the block and any air coming up will want to bleed back to the tank through the bleed hose but when the thermostat opens the air gets sent to the radiator where it gets trapped and can only be removed by opening the radiator bleed bolt. I initially could only get about 3 1/2 gallons in after replacing all my hoses and it took many runs and bleeds before I had put in the required 18 liters. I also had verified how much coolant I had drained by catching it all in a 5 gallon bucket when I started so I know it was 4 3/4 gallons.

This is something I have been battling for the past couple of months but in my case it turned out to be the 1-4 bank head gasket. If you have a leak down tester put as much pressure as you can into each cylinder (probably about 110 depending on your tester and compressor) Let it sit for several minutes and listen for air getting into the coolant through the opening in the tank. FWIW I did several checks with block test fluid and all of them were negative but when pressurizing #4 cylinder I could hear air getting into the coolant system.

Not to say you have the same problem as me but first of all you have to be sure you have put in at least 4 3/4 gallons of coolant (that's a lot of coolant!) because any air trapped in there, for whatever reason, is going to result in the exact same symptoms. Once you have gotten it bled properly you should have no more air in there and should never have to think about it again.

Good luck!

 

I have had coolant coming out of the overflow hose on the expansion tank. I haven't had much of a coolant loss over this time frame. I might have added a small amount of coolant, but it was nothing to be concerned about. I haven't had the thought "Holy smokes! Where has all my coolant gone!?"

I've actually let the coolant run a little low to see if that fixed the problem. I have also bled air out of the system at the radiator during this same time, so this isn't really a scientific test. By running a little low, I still had coolant in the expansion tank, but I might not have been able to touch it when I stuck my finger down the hole.

I haven't tested the cap itself. All I know is that the tester would hold pressure on the whole system for a couple of days at 15 psi.

 

It will spit coolant if you overfill it. I think the manual says 3 cm below filler neck (going off memory) which I interpret to mean the top of the tank so it ends up right about at the seam line which if I remember right is too low for you to touch with your finger.

 

My 328 has always taken several bleeds at the radiator after a coolant change to fully rid it of trapped air. Owned mine since 1988.

 

Just in case, don't bleed the system when hot.

 

My 84 QV also spits out the overflow tube at the filler neck after a drive. The car would be at normal temps around the 195 range. After the drive, I would notice drips on the garage floor. Had a coolant flush late last year or about 300 miles ago. The tank cap is newer, so I wonder if its air in the system? I'm puzzled

 

Thanks Mike. I printed Birdmans procedure and will follow it step by step.

 

I thought Rifledriver stated in an earlier post that having a bit of air in your cooling system is normal, runs within temperature and cooling fan come on you’re good to go.. ( respectfully ) seems you guys may be chasing your tail. You will always have air trapped at the top of the radiator, no way around it due to design. Some of it will naturally gravitate to High Points over time.

 

Mike is correct. Beyond all the 308 inherent cooling issues, spitting coolant is never "annoying, but normal."

 

Is there any benefit to bleeding the radiator on a slight incline to raise the front end?