Cooling System Issues with CAV's?

[Pat Buckley]

After speaking with a few CAV owners recently, it appears that CAV have not set up the engine coolant lines correctly - if you have any input as to your experiences in this area I would appreciate hearing them.

Please see the "Cooling System - Excess Pressure" thread in the Engine Forum here....

Thanks.

[Auto Futura-CAV Factory]

Hi Pat
As you may know, we as Auto Futura have been building the CAV's since car #81. We have also redesigned the car completely, including the coolant system. I am however able to help with any quiries you may have, so please let me know, and lets see how we can help solve it.
regards
Jean

[Pat Buckley]

Thank you Jean - I have sent you a PM.

[Gary Kadrmas]

Wow,

A customer with an issue with his GT40, and the manufacturer chimes in to assist!!!!!!!!!! Thats impressive support!

Way to go CAV!

[Auto Futura-CAV Factory]

Hi Pat
I got your personal mail, but will rather answer it here, so that other CAV owners have the information at hand as well. I have asked an earlier CAV to visit the shop so I can see what they used to do. I can then give a detailed fix for those cars as well as compare to the latest units.
I hope to post such within a day ar two.
Best regards
Jean

[Pat Buckley]

That would be great - thank you.

I look forward to the information.

[Canuk40]

Hi Pat,

Just what's happening? Does the car go from cold to boiling, or warm up normaly but then peak the temperature gauge when you get on it? Do you get hot air from the heater as the temp gauge rises?

Here's what we've found on early cars:

a) The header tank is on the blocked off side of the heater circuit so you can't fill the cooling system without the heater valve propped open. Also I like to drive slowly until the temperature comes up, with the heater on so I know it's got hot water. Then turn off the heater and you should be okay.

b) The Header Tank must be filled above the height of the thermostat housing on the block or your thermostat won't open, never a good thing. Of course this leaves little room for expansion so a separate overflow can must be used. We put a 1 liter tank on the firewall or beside the transaxle for this purpose.

c) The fans may not always turn on when they should, especially if coolant levels are off. You'll get no hot water at the rad if the thermostat doesn't open so the rad fans won't see a turn on signal. The sending unit for the temp gauge also will not read if coolant levels are off.

d) In hot climates I'm inclined to run without a thermostat. Just knock the guts out of one and install the flange back in the housing. If you take out the thermostat and don't put the flange part back in you'll get coolant leaks. No thermostat means the car runs at an idicated 80c which is fine unless you're running a current EFI system that needs at least 90c to work. Anyways, 80c indicated is still much hotter in the heads. This also reduces water pressure in the block.

e) Consider going to Evans Coolant in place of antifreeze or water wetters.

That should get you sorted, please feel free to use the toll free number if you have any questions.

Cheers

[Pat Buckley]

Thanks Ian -

What happens is that it will idle for an hour, the fans will cycle, but as soon as I rev it to over 3500 coolant blows out the resevoir.

I think the main problem is that the t-stat housing bypass goes to the bottom of the coolant resevoir.

So with a 5/8" pressurized line going into the resevoir and only a bleed line out of it, whenever I rev the engine over 3500 the pressure in the reservoir shoots up and the coolant blows out the overflow line.

I am advised that the fix is to run the t-stat bypass into the waterpump ( I still need to figure out which port to use) and to run a line from the suction side of the waterpump to the bottom of the resevoir.

Regards,

Pat

[Canuk40]

Hi Pat,

I know where you're coming from, however it's making my head hurt...

The bypass should connect to the water pump inlet, use the upper of the two tubes. The lower one is for heater return.

What bothers me is that the entire cooling system operates at the same pressure because it's a hydraulic system. The only reasons for pressure changes is a drop caused by cooling at the rad or an increase caused by resistance to the water pump. Or by localized boiling which can happen almost instantly.

If the thermostat is fully open there should be no huge rise in coolant pressure. This tells me either the thermostat is not openning or you're getting localized boiling in the heads or both.

Something else we've seen, and this caused me no end of grief because it had nothing to do with the car was: excess silcone used on the head gaskets was partially blocking the coolant passages in the heads to the block and incredibly also on the manifold gaskets to the intake at the crossover feed to the thermostat housing. Wow, that one drove me nuts...

So IMHO you've got air in the system, no doubt since pucking out the resovoir, and your thermostat / temp gauge is lying to you. There's probably enough coolant in the car to make it seem alright but you have air in the heads and this is not a good thing unless you've got a Rotax in there

Do you have a port on top of the manifold behind the thermostat you can open, say by taking out a sending unit or pipe plug? I'll bet you'll find nothing comes out of that hole when the engine has cooled overnight. There's your problem. When the header tank is full enough and there's no air in the system, you will get coolant out of that port, lot's of it!

The bypass still has to be sorted and the bottom of the header tank should "T" into the feed line of the heater in the right rear sill. No fun to get at, but that's where the union is.

Hope that helps Pat. Warming up these cars slowly really counts too. I mean ten minutes should do it. The radiators a massive, you should have no problem keeping the temp down.

Cheers

[Auto Futura-CAV Factory]

Hi Ian
Thank you for your input. I must agree on the header feed pipe. IT HAS TO BE CONNECTED TO WATERPUMP.I have had a car brought to me where the chap had fitted his own engine, and fitted the header tank hose down onto the thermostat bypass. Need I say more...? The same scenario as Randy.

The new CAV's are not plumbed into the heater hoses. That way the owner can check feed to engine, and when the ^@%$^ hits the fan in the heater circuit, one can blank it of and still drive home easily.

Points to remember: Header tank feed onto waterpump. Heater is a loop..from thermostat by-pass through heater core and back to waterpump. Header tank level must be higher than thermostat. ( we sell bigger and higher tanks that would fit earler CAV's) Remove thermo sender or something similar from highest point on engine, and bleed out any air. Even lift rear of car, BUT GET ALL THE AIR OUT.

Please shout if I can help further.
Good luck!
Jean

[Auto Futura-CAV Factory]

Sorry Pat, not Randy. Getting names mixed up with E-mails of this morning..