Coolant

[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

[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!