Coolant

[Jonty]

Hi all

I’ve noticed a few times that I’m getting a small amount of coolant coming out my overflow when I park up. I’m not losing any material amount of coolant and I’m not needing to top up. I’m also not overheating and the fans work correctly. I have my water pump done a couple of months ago. Anyway I opened the overflow cap and there’s plenty of bubbles in there. I ran it for a bit in this video. It doesn’t appear to be “boiling” but should I be worried about a head gasket?

https://youtu.be/LYyB6d9Gx8c

[Jonty]

Also my radiator cap is fairly new from DGo. When I get the engine up to temp just before the fan come on is when I notice the overflow leaking slightly. If I lift the release valve on the cap it will spew coolant.

[Jonathan]

It's too full. Aim for about halfway up that reservoir. You can peer in and see the backside of the weld that holds that front bracket on... use that as a guide. It expands when it is hot, so assess the level when it is cold.

[Jonty]

Thanks Jonathan

I checked this morning when cold. Even after a dump of 100mls or so when I lifted the relief valve when hot it’s still over half full so will take a bit more out and get it below that weld mark thanks. The thing that concerned me was all the bubbles. Is this normal?

[Jonathan]

I wouldn't consider bubbles normal, no. How or why they are there though... It could be just the coolant getting mixed/agitated more than usual because the tiny little return line would be coming in under that level you showed. I would get the level down first, monitor for bubbles and then reevaluate.

Keep in mind what you are doing by removing that cap while the system is still hot and under pressure. By the system getting to just under 15 psi, it is effectively raising the boiling point. If we were talking just plain water, it would boil at atmospheric pressure at 212 deg F. Raise the pressure though and the boiling point goes up. You determine that kind of thing looking at what they call steam tables. Well, a stationary engineer operating a boiler would. We won't be. :) What I'm getting at is if you have a coolant temperature higher than what it would normally boil at while under no pressure, the second you take the cap off, you're bringing it back to atmospheric pressure and that coolant will flash to steam immediately. And you can get a lot of steam for a small amount of liquid water.

So I might recommend you wait for the system to be cold and then suck the necessary amount of coolant out using a turkey baster or something similar. A little less hectic doing it cold than hot. I used to work as an engineer in nuclear and we had some very large reactors and turbines there. The reactors were approximately 3 million horsepower of thermal energy and the intent was to make steam out of as much of it as possible. You do not want that kind of system breaking open to atmosphere. Not at 1,500 psi and 310 deg C. It would be lights out to anyone in the building in an instant if that ever happened.

[Jonty]

Great advice thanks Jonathan. Yes the return line was under the level so it might be just as a result of coolant being stirred up. I’ll suck some out and then then what happens. If I’m still getting bubbles I’ll try one of those test kits for exhaust gas in the coolant

[Jonty]

Hi Jonathan

Emptied it below half and took it for a drive and it’s still leaking plenty of coolant in a foamy state. I think I’m down a head gasket

[Jonathan]

Hi Jonathan

Emptied it below half and took it for a drive and it’s still leaking plenty of coolant in a foamy state. I think I’m down a head gasket

Sorry to hear that. Time for that exhaust gas testing in the coolant you mentioned.

[David T]

I agree, time to test for combustion gases in the coolant. If you have a coolant system pressure tester, one quick test is to see if the pressure builds up fast. Just put the tester on the system, pump it up to about 5 psi and watch it with the motor running. If it climbs quickly, you probably have a bad head gasket. Can't tell you which side but best to both sides anyway.

[Jonty]

Hi all

Well bit of an update on this. The car passed the gas test and ordered a full compression and leak down test and all passed. The mech actually said it had amazing compression (160-154 across the the board). They are now really baffled as they are convinced it’s not the head gasket. They are at a bit of a loss but are wondering if it could be a contaminant in the coolant (sounds unlikely) or there is a small leak somewhere. They did full system pressure test and it was fine and there were no leaks. Really baffled

[David T]

Other possibilities that can cause overheating and loss of coolant;
Timing not set properly
Not properly bled and air still in the system
Collapsing hose on the suction side of the water pump blocking coolant flow
Radiator plugged up
Impeller damaged or loose on shaft of water pump
Stuck thermostat/wrong thermostat
Cooling fans not working right, bad circuit breaker, bad "O" switch, fans running backwards, etc
Something blocking the air inlet grill like a license plate
Bad/wrong pressure cap

[Jonty]

Other possibilities that can cause overheating and loss of coolant;
Timing not set properly
Not properly bled and air still in the system
Collapsing hose on the suction side of the water pump blocking coolant flow
Radiator plugged up
Impeller damaged or loose on shaft of water pump
Stuck thermostat/wrong thermostat
Cooling fans not working right, bad circuit breaker, bad "O" switch, fans running backwards, etc
Something blocking the air inlet grill like a license plate
Bad/wrong pressure cap

Thanks Dave


Will check all that but timing was checked and it’s a new water pump so will go through the rest. The radiator cap was faulty but it was holding too much pressure (20psi) so have a new cap coming. I don’t think more pressure would be the issue.

It’s the foaming of the coolant that has us all confused

[Parzival]

I used to think bubbles in the overflow was sure sign of a blown head gasket. I would get bubble in there if I revved the engine whilst looking in there. I did the combustion gas check, idling and revving and everything else, I even did it for 4 minutes instead of for 2 like the instructions state, test fluid never turned yellow. Then I looked at all my friends and local club members cars, they ALL bubbled in the reservoir when revving. I checked 4 or 5 Delorean's, its probably just churning it up in there from the circulation. The thing is, our cars don't really have an overflow, its a reservoir, and the coolant is circulating in there. I don't think mine bubbles when idling though.

On the coolant level, and puking out the tube.
Important to note here that it's half full when cold, if you look at it hot or even warm it will be more full.

My over flow is half full (cold), and I don't get any coolant puking out of the tube, even if I drive to Orlando and back (about 60 miles each way) But if I full it up too much, then some will come out until its back to slightly more than half, and then the tube will always be bone dry even after long drives, not even a hint of moisture.

If it keeps puking out the tube even after you lower the level, and it bubble excessive then perhaps you will need to worry.

[Jonty]

I used to think bubbles in the overflow was sure sign of a blown head gasket. I would get bubble in there if I revved the engine whilst looking in there. I did the combustion gas check, idling and revving and everything else, I even did it for 4 minutes instead of for 2 like the instructions state, test fluid never turned yellow. Then I looked at all my friends and local club members cars, they ALL bubbled in the reservoir when revving. I checked 4 or 5 Delorean's, its probably just churning it up in there from the circulation. The thing is, our cars don't really have an overflow, its a reservoir, and the coolant is circulating in there. I don't think mine bubbles when idling though.

On the coolant level, and puking out the tube.
Important to note here that it's half full when cold, if you look at it hot or even warm it will be more full.

My over flow is half full (cold), and I don't get any coolant puking out of the tube, even if I drive to Orlando and back (about 60 miles each way) But if I full it up too much, then some will come out until its back to slightly more than half, and then the tube will always be bone dry even after long drives, not even a hint of moisture.

If it keeps puking out the tube even after you lower the level, and it bubble excessive then perhaps you will need to worry.

Thanks for this. My plan is to replace the cap and ensure cold coolant level is around 1/3 full then see how it behaves. If it’s still overflowing I’ll start working through the system to see if there is a small leak somewhere (could even be a small hole in radiator in can’t see as it’s original). I have heard of water pump cavitation which causes a coolant foam.

[Parzival]

Thanks for this. My plan is to replace the cap and ensure cold coolant level is around 1/3 full then see how it behaves. If it’s still overflowing I’ll start working through the system to see if there is a small leak somewhere (could even be a small hole in radiator in can’t see as it’s original). I have heard of water pump cavitation which causes a coolant foam.

Yes, the fear is that combustion gasses are pressing into the cooling system, and displacing coolant in the heads and block. Once the coolant is getting displaced by combustion gasses it has no place to go but out the overflow.

Possibility 2 is that your system is not holding pressure in the cooling system, keeping the boiling point of your coolant low, the coolant will boil around the liners in the block, and like above, the steam will displace coolant and boom... same effect.

[David T]

Have to be careful not to confuse bubbles with "churning". Actual bubbles would indicate dissolved gasses. That happens either from air not being bled out of the system or combustion gasses leaking into the coolant, usually from a head gasket due to overheating. Since the combustion chambers are a much higher pressure than the cooling system, any leak will allow the gasses from the combustion chamber to get into the cooling system. You can put a cooling system pressure tester on and watch it and if you see the pressure go way up fast (faster than from just the coolant getting hot) that is a good indication you have a bad head gasket. The definitive test is a combustion gas analyzer to confirm the presence f combustion gasses in the coolant.
Trapped air is from either the system not being completely and properly bled when filled initially OR, you have coolant leaks and when the system cools off and the coolant contracts you can suck air into the system. That can be confirmed by seeing obvious coolant leakage or you have to add coolant because it is leaking out. On a Delorean you can have a lot of leakage and not see it because it leaks under the intake manifold and then gets evaporated so the tell is if you have to always add coolant. Of course if you have a blown head gasket you will also be adding coolant because it will be getting blown out because the leaking combustion pressure will over pressurize the cooling system above 15 psi. The cap will pop to relieve the pressure and some coolant will get out too.

[CFI]

Thanks Dave


Will check all that but timing was checked and it’s a new water pump so will go through the rest.

Just because a part is new does not mean it’s working correctly. Someone recently had an improperly machined water pump that was defective right out of the box.

[Mark D]

..."churning"... bubbles


https://www.youtube.com/watch?v=20soJuwWFH4

[Jonty]

Have to be careful not to confuse bubbles with "churning". Actual bubbles would indicate dissolved gasses. That happens either from air not being bled out of the system or combustion gasses leaking into the coolant, usually from a head gasket due to overheating. Since the combustion chambers are a much higher pressure than the cooling system, any leak will allow the gasses from the combustion chamber to get into the cooling system. You can put a cooling system pressure tester on and watch it and if you see the pressure go way up fast (faster than from just the coolant getting hot) that is a good indication you have a bad head gasket. The definitive test is a combustion gas analyzer to confirm the presence f combustion gasses in the coolant.
Trapped air is from either the system not being completely and properly bled when filled initially OR, you have coolant leaks and when the system cools off and the coolant contracts you can suck air into the system. That can be confirmed by seeing obvious coolant leakage or you have to add coolant because it is leaking out. On a Delorean you can have a lot of leakage and not see it because it leaks under the intake manifold and then gets evaporated so the tell is if you have to always add coolant. Of course if you have a blown head gasket you will also be adding coolant because it will be getting blown out because the leaking combustion pressure will over pressurize the cooling system above 15 psi. The cap will pop to relieve the pressure and some coolant will get out too.

Thanks Dave but just to be clear it has had every test under the sun, pressure, compression, leak down, gas analyser and it has all passed so they are confident it should not be head gasket

[Jonty]

Just because a part is new does not mean it’s working correctly. Someone recently had an improperly machined water pump that was defective right out of the box.

Ha ha that was me and my first pump! If this second one is dodgy I won’t be happy!

[David T]

I understand you did a lot of tests and they all came back negative. If "foaming" is what has you concerned, maybe the coolant is contaminated in some manner. Maybe flush the system out and refill with fresh anti-freeze and soft water.

[FABombjoy]

A Jacuzzi will get foamy if the pH is too far off. And what is a cooling system if not a terrible little slimy Jacuzzi?

[iflights]

Ha ha that was me and my first pump! If this second one is dodgy I won’t be happy!

What was the defect in the original pump? Could it have contaminated or spewed something into the coolant passages?

[CFI]

What was the defect in the original pump? Could it have contaminated or spewed something into the coolant passages?

One of the coolant passages was never machined out. The coolant had nowhere to go. Do a search, there’s several pics on this forum.