V12 gurgling but normal temp indicated

I’m new t this Forum. Have S1 and S2 but just purchased my first S3 e-type and I’m getting acquainted with the many differences.

I took it out for a spirited run on 75 degree evening for about 40 miles of highway driving. When I retuned I noticed a gurgling noise and some coolant dripping from the overflow tube on the coolant expansion reservoir onto the garage floor. Hadn’t noticed this before and the indicated temp on gage was normal (lower to mid-scale throughout the 60 minute drive. Also, the fans appear to be working normally.

I know overheating is very dangerous with these engines, and I’m wondering what I could check to alleviate my concerns.

Have a listen.

Sounds like either the system is not pressurized or you have an air pocket; check the radiator cap and pressure test the cooling system. Bleed the cooling system to remove the air pocket.

Could it be that you have the spring loaded pressure cap and the fixed pressure in the wrong place…?? The fixed cap should go over the engine whereas the spring loaded is for the expansion tank, or maybe I have that the other way round…

Is there a way to check if there may be exhaust gasses in the cooling system? (indicating a Blown head gasket)

I can think of several ways to detect a blown head gasket, having experienced one in my’58 MK1. One is to get a Combustion Leak Detector, such as this one:

Another way is to fill the expansion tank to the top, start the engine, and look for a continuous stream of bubbles coming out of the filler neck. Additionally, you could remove the plugs and look to see if one is substantially cleaner than the rest, since it is being steam cleaned while the engine is running. While the plugs are out, you could pressurize each cylinder (or just the one with the clean plug) and see or listen for bubbles in the filler neck. I built a pressure adapter by removing the ceramic from an old spark plug, brazing in a 1/4" pipe nipple, and screwing on an air coupler.

That said, gurgling when the engine is not running does not suggest a blown head gasket to me. To me it sounds like a case of heat soak, where the water stops circulating but the engine is still hot enough to boil it. I have wired my fans to not be shut off with the key. That way they stay running until the Otter switch is cool enough. That usually takes about a minute. The water will continue to circulate through the radiator by convection (or percolation) when the engine is off, and the fans will also directly cool the engine.

On my V12 the expansion tank is the only place there is a radiator cap, and it is located above the engine and radiator, and has several hoses to bleed air to it from other spots. It would be very difficult to have an air pocket.

2 Likes

Just had a reoccurrence of the overflow after a spirited drive in about 80 degrees outside temp and 20 Miles. After turning off the engine, I noticed steady stream of coolant coming from the outflow tube; Engine temp normal, and fans running normal. I let them run after engine stop and they ran for about 5 minutes then turned off on their own.
Is it possible that the 13 PSI radiator cap is opening under less pressure? Is 13 PSI correct?

Walter, i am not an e type owner. Have a 6.0 liter v12 XJS. The long answer below is based on my v12 XJS set-up.
The XJS has a fill point in the crossover tube that connects the two banks. This fill point is where to check and re-fill coolant. On acold engine.And should have a cap that is higher psi than the expansion tank.
The XJS expansion tank is in the left fwd side of the engine bay and should really only be opened when doing a re-fill after draining the coolant. Open both the crossover and the expansion caps and the bleed valve on radiator and SLOWLY fill the servicing point on the crossover tube till you see coolant coming out the bleed screw. Then close the bleed. The expansion tank will slowly fill during this as well. Expansion tank is the point where expansion releases pressure…and this release goes to an atmospheric tank in the left fender behind the wheel. Excess pressure bleeds to atmos tank and as engine cools the fluid is pulled back into the expansion tank. So opening the expansion tank cap releases the seal between the expansion tank and the atmospheric tank. And fluid doesn’t get returned into the system.

The gurgling makes me think there is possibly abad seal at one of the radiator type caps or at one of the many hose clips. You can buy a Stant coolant system tester for about 25 dollars US. It will allow you test radiator cap actual pressure. I have found brand new caps that did not pressurize to their stated level. The tester will also allow you to pressurize your coolant system and then you look for leaks, or leave it and see if pressure holds or drops.

Sorry for long reply

Thank you for the detailed information! I will study how to apply this to my E V12 which is the same or similar engine I believe

hello Jeep_dude
if the cap are dubious, I would change them for the peace of mind
they’re cheap and easy to change for new ones

The v12 etype is different from other v12s. There is only one cap and it is on the header tank in the middle of the car, between the engine and the radiator.

The high point in the cooling system is at the left hand rear of the engine going through the heater matrix. To effectively bleed the system, you have to run the engine and open and close the right pull hand of the two pull levers left of the centre clocks. (The other one simply opens an air flap on the bottom of the heater box.) It helps to point the car uphill when filling with coolant.

The water in the header tank will be expelled such that the water level settles at just below the half way mark of the header tank. Refilling the header tank above half way will simply mean the excess is puked out again.

If the gurgling sound you are hearing is after turning the engine off, then that is simply hot water syphoning out of the heads and through the top pipes.

If you are worried about overheating post shutdown, see my post about heatsoak from a while back.

kind regards
Marek

Hello Marek

Thanks again for your counsel. Yesterday my car again “spit up” after a 30 mile drive even with new cap. When I shut down, I turn the key to run the fans till they stop; less than 2 minutes. It’s a few minutes after they stop that the spitting occurs, this time about 1/2 pint. As you suggest I guess this must mean that the engine is still hot enough to cook the remaining gallons to boil and thus pushing some out the overflow tube. Does this have potential to cause damage? Will this continue even as the coolant begins to lessen in the system? I don’t seem to hear gurgling anymore. I’m concerned since I’m hesitant to drive the car. The PO stated the coolant was recently replaced, but is it possible it is less than adequate to raise boiling temp sufficiently?

No, it’ll stop as it’d push out the air sitting in top of the header tank instead and so the coolant level would be unchanged once it has settled out.

You shouldn’t be hesitant to drive the car - there is plenty of coolant circulating whilst you are driving and a functioning radiator is part of the circuit.

The boiling point is dictated by the cap. Water boils at a higher temperature if it is at a higher pressure.

A few minutes after you have stopped, run the engine for 30 seconds. That’ll swap your reservoir of fan cooled water sitting in the radiator (which did you little or no good as it hasn’t gone back into the engine) with the hotter water still cooking in the heads. It’s cheap easy, free and it works a treat.

kind regards
Marek

Thanks again Marek, I tried the staged shut down recommended from the graph with good affect. I will continue the practice especially on warmer days. But could I help alleviate the issue with a lower temp thermostat?

No.
That’ll have no effect whatsoever.

kind regards
Marek

1 Like

Are you sure that this is just not normal? Ive had my v12 Etype for over 30 years. If I fill up the radiator tank to the top, on the first drive, it will always spit out a small amount of water. After that no issue. Jeff S. Atlanta, GA

Cars without the recovery tank need the air space that is being created when the excess is spit out.