coolant in catch can after one hour on track

[docford]

Hello there,

it seems that my XKE has some sort of a coolant issue. Whenever we just drive on the streets, everything is fine, but when we race it at the track, it pushes out coolant in the catch can. After one hour of sustained track time (Spa for instance) the catch can is full, which is about 1 Liter of green cooling fluid.

When the motor cools down, it suck about 250cc back into the radiator. We had the radiator filled cold to about 1/2 inch below the expansion tank cap.

My first guess was a failed head gasket, but the is no mayonnaise in the oil, all 6 spark plugs look good and there is no CO gas in the cooling liquid (tested with a chemical revealing device).

The compression check (engine warm) showed the following values:

cyl.1 13.0 bar
cyl.2 12.5 bar
cyl.3 12.5 bar
cyl.4 12.0 bar
cyl.5 11.5 bar
cyl.6 11.5 bar

Would you have any idea of what else I should check ?

What should be the correct filling level of the radiator when cold ?

[malcolm]

On my series 2, I fill to about 2 or 3 inches below the cap, otherwise I similarly lose fluid. Think you're filling too high, but other S1 owners may correct me. I did 25 laps at Goodwood filled to that level, and didn't need to top up.

[christopher storey]

Several points :

1. Your photo from Spa shows 2 objects in the duct in the bonnet leading to the radiator. Whilst they are not very large, at speed they will create turbulence in the airflow which will affect cooling. Since the S1 was always a bit marginal on cooling, this will not help

2. The system you have , with what you describe as an expansion tank, sounds like either an S2 system or some sort of hybrid . If it is such a system, then it is vital that the radiator cap is NOT a pressure cap, ( thus allowing free flow in both directions to and from the expansion tank ) but that the expansion tank cap IS a pressure cap

3.As already suggested, try lowering the coolant level a little and see if this makes a difference

[abowie]

If the car is running OK and not overheating, in the absence of other evidence I would suggest that the cooling system is just finding its own level.

[PeterCrespin]

I would suggest that the cooling system is just finding its own level.

Correct. And a previously settled system will puke a little extra, even if not topped up, each time the engine gets significantly hotter than its previous hottest level. Chris's comments about rad caps on the S2 system are correct, but this sounds like the normal S1 system configuration, albeit using custom parts. Having the overflow from the rad pressure cap submerged in an atmospheric catch tank will simply mean that expelled coolant will be sucked back into the tank past the pressure cap, on cooling.

[christopher storey]

Having the overflow from the rad pressure cap submerged in an atmospheric catch tank will simply mean that expelled coolant will be sucked back into the tank past the pressure cap, on cooling.

Are you sure, Peter ? If the rad has a pressure cap, this prevents the expelled coolant being sucked back as the system cools, because the spring loaded pressure cap seals off the overflow ( in this case inflow ) pipe from the radiator itself ??

[PeterCrespin]

[Edit: Apologies, I thought this was a private message]

Hi Chris, nice to hear from you.

If you look under the cap you will normally see a disc about the size of an old shilling that is lightly held closed when off the car but pressed tight by coolant pressure in service. On cooling, if there is fluid held in the annulus between the two main seals (the sprung and outer seal), and if one of these discreet little valves is present, the reduced pressure sucks coolant from an open-to-atmosphere catch tank back into the rad. Without a catch tank it just sucks air in. Otherwise, without a return valve you'd get collapsed hoses on cooling after expulsion of coolant.

I always like air-cooled engines myself!

Best wishes
Pete

[christopher storey]

Ah, Peter, thank you for that explanation. I had not considered that air could not get back in if my hypothesis had been correct . I must look more closely at the caps on mine !

I hope all is well with you and yours

[docford]

[Edit: Apologies, I thought this was a private message]

Hi Chris, nice to hear from you.

If you look under the cap you will normally see a disc about the size of an old shilling that is lightly held closed when off the car but pressed tight by coolant pressure in service. On cooling, if there is fluid held in the annulus between the two main seals (the sprung and outer seal), and if one of these discreet little valves is present, the reduced pressure sucks coolant from an open-to-atmosphere catch tank back into the rad. Without a catch tank it just sucks air in. Otherwise, without a return valve you'd get collapsed hoses on cooling after expulsion of coolant.

I always like air-cooled engines myself!

Best wishes
Pete

yup, that is what happens once it cools down.

[docford]

If the car is running OK and not overheating, in the absence of other evidence I would suggest that the cooling system is just finding its own level.

Ok, we'll keep running it and see if the spillage of coolant stops after a while.

[docford]

...
2. The system you have , with what you describe as an expansion tank, sounds like either an S2 system or some sort of hybrid . If it is such a system, then it is vital that the radiator cap is NOT a pressure cap, ( thus allowing free flow in both directions to and from the expansion tank ) but that the expansion tank cap IS a pressure cap
...

Thanks for your reply.

the radiator is directly connected to the expansion tank by one big hose. Inside the expansion tank go two lines, one from the water pump (must be coolant return from engine block) and one from the intake (must be cylinder head coolant return).

There is no cap on the radiator, just a hose going in on the top and another one going out to the water pump om the bottom. The expansion tank has a pressure cap. We started with 14 lbs cap, then went to 18 lbs and finally 21 lbs in order to contain the spillage, but that did not do any difference. What pressure setting would you recommend ?

[christopher storey]

I certainly don't recommend those very high pressures : 7lbs at low altitudes, or if you are in the mountains perhaps 13 lbs, should suffice. 21 lbs will be putting a great strain on hoses , gaskets etc, not to mention on the structure of the radiator itself and on the water pump gland

[docford]

thanks for your reply. I’ll give it a try with a 7 lbs cap.

Would you know where to find a drawing or exploded view of the water pump ?

I’m wondering if it cavitates, when driving continously on the teack between 3,500 and 6,500 rpm, and therefore creates air bubbles,

[mgcjag]

Can be found in the service manual....and in the Knowledge base section ...technical documentation viewtopic.php?f=16&t=700 series 1 cooling system ..also worth looking at you thermostat rating....or are you not running with one when raceing.... Steve

[docford]

right, the thermostat is not mounted.

Thanks for the link to the drawing.

[PeterCrespin]

What have you done to block off the bypass meant to be blocked by the open tstat?

[docford]

What have you done to block off the bypass meant to be blocked by the open tstat?

Good question ! I need to check that ! Is the bypass hose the one which connects to the elbow of the water pump inlet tube ?

[PeterCrespin]

From tstat housing yes. Block it with anything in the hose heat and waterproof like a slice of nylon bar or alloy etc..leave it slightly loose or drill a small hole to permit slight circulationcv

[docford]

I went to the shop this evening and took of the hoses and expansion tank to get a better understanding. The puzzling thing is that a big water hose goes from the intake manifold to the expansion tank, which is OK, and right underneath it, at the expansion tank, another big hose goes to the water pump bypass. It looks as if not all of the cooling fluid will then circulate through the radiator



I unbolted the tank and took a look inside. The return hose goes to a tube inside, which aims at the exit of the trank, which goes in the top of the radiator. So far, fair enough. However the tube is not continous and a substantial amount of cooling fluid goes to the other opening, after being circulated around a flat sheet of metal inside the tank, to the other exit and right into the water pum bypass inlet. There is no restriction in the bypass hose whatsoever.




The whole steup is quite intriguing. Have you ever seen anything like that ?