Cooling System - Excess Pressure

[Pat Buckley]

Pat - Make sure you have new head-bolts for that engine. I recommend ARP. Many of the OEM head-bolts are torque-to-yield and can only be used once. If you re-use them, they don't torque right - just stretch..

Thanks Randy - I am using ARP bolts.

Jac - I did the test you recommended - no bubbles at all in any cylinder. I applied about 110 psi for about 20 seconds each.

Is this what they call a quandary?

Do I take the kind of easy way out and assume the head gasket and cylinder walls are OK, re-route the coolant lines and re-assemble?

Thoughts?

Thanks again.

 

[Frank Catt]

Pat, we had several issues with the CAV cooling system, and the advise you have from all of the above is valuable. We also ditched the existing expansion tank and made a new ali tank more as original, at a much higher level to assist air bleeds. We also found it essential to alter or add air bleeds into the radiators that were above the full bore of the coolant pipes, the original CAV position of bleed pipe back to the expansion tank is set too low to ensure that all trapped air is removed from the top of the rad, and thus preventing full flow through the main service pipes.

 

[chuck smith]

I do not see the relationship between a faulty cooling system setup and combustion gases in the coolant. You have proven you have that issue so I still believe it is the gaskets with a block defect a distant second. Not that the cooling system routing could not be better, but how can that add combustion gases to the coolant?

 

[Pat Buckley]

I do not see the relationship between a faulty cooling system setup and combustion gases in the coolant. You have proven you have that issue so I still believe it is the gaskets with a block defect a distant second. Not that the cooling system routing could not be better, but how can that add combustion gases to the coolant?

Good thought.

I did replace the right head gasket already, Chuck. Subsequent use of chemical test showed no color change so I guess that is another bit of information that would support just doing a coolant line re-route.

 

[Pat Buckley]

Pat, we had several issues with the CAV cooling system, and the advise you have from all of the above is valuable. We also ditched the existing expansion tank and made a new ali tank more as original, at a much higher level to assist air bleeds. We also found it essential to alter or add air bleeds into the radiators that were above the full bore of the coolant pipes, the original CAV position of bleed pipe back to the expansion tank is set too low to ensure that all trapped air is removed from the top of the rad, and thus preventing full flow through the main service pipes.

Thanks Frank - I did also recently install an aluminum resevoir and positioned it higher than the stock CAV unit.

As to the bleed at the radiator - as part of the bleed process I jacked up the left side of the car which raised the bleed point substantially above the full bore of the right side coolant pipe.


Pat


It occured to me that perhaps something as simple as installing a 3/16" restrictor in the line from the t-stat housing to the resevoir may be all that is required?

 

[Jac Mac]

Pat,

1. Does your current header tank have a line from the bottom going back to the lower heater hose fitting (5/8" bore )- if not make it happen.

2. Fit the -3 ( 3/16 line ) from the highest point on the manifold / t/stat area to the side of your header tank similar to Chucks photo at about 3/4 height or slightly higher.

3. If you are running a restrictor plate rather than thermostat then block off the bypass entirely.

4. If you still use a thermostat I feel that the bypass could do with a restrictor of approx 1/4" dia in any rear engine application to promote flow forward thru the radiator.

5. Its your call as to whether you refit exhausts & test at this point or remove replace head gaskets, given that you apparently have a suspect hose routeing problem ( that sounds awful dont it! ) I would take the easy way out & check that first, but then I'm old and hate doing things that are not reqd!.

cheers
Jac Mac

 

[Pat Buckley]

Jac -

1. I am not using a heater (California benefit - one of the few) so if you could suggest an alternate place to attach this line I am all ears...

2. I will do this and "T" it in to the line from the top of the radiator as well.

3. I was running a restrictor plate but have switched to running a t-stat as it took forever to warm it up. (unless I revved it up, of course!)

4. Will do.

5. TBA

Thanks again.

Regards,

Pat

 

[Jac Mac]

Pat,

1.. The hose fitting should already be there on your water pump directly below the one that the bypass is fitted to. It may have a rubber cap over it or the pump may have a blanking plug screwed into the threaded hole. Remove that cap/plug & fit the appropriate hose stem or fitting if reqd to attach the hose from the bottom of the header tank. Good Luck, I 've gotta go put some fence posts in to keep the cattle out of the garden!

Jac Mac

 

[Rick]

The head gaskets on the LH bank have to have the gasket inverted to force the water through the engine & heads correctly. I use the Fel Pro 1011-2 and it is a single gasket with the word "Front": stamped on one end (front) end when installed on one bank. It is easy to overlook inverting this on the other bank of cylinders. If done incorrectly the word "Front" will be visable to the rear when installed on one bank I think most other SBF head gaskets are similarly stamped.
As far as the hoses, by comparison, 289 FIA Cobra type has one of the small water pump hoses (5/8") into the bottom of the surge tank. The other similar (5/8") pump outlet is connected to the thermostat housing w (when using a thermostat). A 3/8" air bleed hose go from high pint on radiator to spigot on side of surge tank at about "3/4 full" level". This being how the air is bled from the radiator when filling.

 

[Jim Dewar]

Hi Pat, Please post the results of your fix. I'm very interested, since I have a similar problem. This is a very good thread!!

 

[Pat Buckley]

I re-outed the coolant lines.

The line that goes to the bottom of the header tank was originally attached to the t-stat bypass which is a high pressure 5/8" line. This resulted in the header tank getting pressurized as the only other way out of the header tank was the 3/16" bleed line. Because of this the radiator cap was the only way for the pressure to relieve, which it did, causing coolant to escape into the overflow tank.

The 5/9" line from the bottom of the header tank now goes to the intake side of the water pump.

So far so good.

I am surprised though, at the difference in the coolant level when the system is hot vs cold.

 

[Jim Dewar]

Hi Pat, Were the headgaskets blown or was it only the coolant hose routing?
My coolant reservoir holds approx. 1 Qt. and when cool the level drops to about 1 cup. I am always suprised at the amount of expansion. Thanks for your response!

 

[Pat Buckley]

Hi Jim,

The headgaskets were OK as it turned out.

My coolant reservoir is about a quart capacity and between hot and cold it will be either full or empty. (?)

I am considering adapting a see through reservoir from a production car -

 

[Randy V]

Glad your headgaskets were fine.. While it was certainly a PITB to verify them, you can at least now put that concern out of the picture.

You know - the more I think about it the more I think we need something with about half-again more capacity for a coolant recovery tank. For smaller cooling systems, the 1qt is fine. Our systems hold a lot more coolant and therefore can expand just that much more than your typical car's cooling system.

I did a 427w along with a 19x31 3 row radiator for a Cobra that I did a few years back. That car would suck a full 1qt reservoir dry - thereby introducing air into the system. I ended up using a 2qt custom tank on that car and never looked back. As far as I know the customer is still pleased with it..

 

[Pat Buckley]

Thanks for the thoughts, Randy.

I think I will adapt a 2 quart reservoir - that makes sense.

 

[Peter Delaney]

Pat, a friend of mine who has a DRB (Windsor) did some investigation on the cooling system expansion issue. He found that the whole system held about 18 litres, and that cold to hot expansion was about 1.8 litres, & solved the capacity problems by fabricating a larger 3 litre (about 3 US Quarts, I think) expansion tank.

On the other hand, I am still using the smaller original DRB tank, & have had no problems (apart from when I had a leak !). So I think it probably comes down to the varying coefficients of expansion of the major component materials used (principally the radiator & main pipes).

As with many things, bigger seems better !!

Regarding what type of tank to use - a plastic one from a production car is the easiest & fastest way out. But if you want an "original look" (whatever that is), you could fabricate a big alloy one & fit a sight-tube (similar to that used by Dimi on his gearbox) - see thread :

http://www.gt40s.com/forum/gt40-tech-powertrain-transaxles/24391-g50-gearbox-oil-level.html

I'll get around to fitting one to my tank, just so I don't get any more burned fingers whilst checking hot levels !!

Kind Regards,

Peter D.

 

[Pat Buckley]

Thanks Peter -

1.8 litres - wow. I guess with the huge radiators our cars have, this is to be expected.

I like the idea of a sight tube.

So, it looks like I am in the market for a 2 quart coolant reservoir with a sight tube.

 

[Chuck]

Canton makes a 2 quart aluminum tank with a sight tube. #80-201. I was debating about either the 24 ounce size (80-206) or the 2 quart. Sounds like the 2 quart would be better.

Does anyone have any experience with either of these reservoirs?

Location: Obviously the expansion tank needs to be mounted as high as possible but I assume that the reservoir can be mounted lower. It would be hard to find a high spot large enough for a two quart reservoir in addition to the expansion tank. I was contemplating finding a spot at the aft end near the transmission, where there is a bit more space.

Will this work?

Here is the Canton page:

http://www.cantonracingproducts.com/tanks/catch_tanks.htm

 

[Geoff Hurrell]

I missed this thread when it started unfortunately. I had the same problem initially with my CAV and it was simply that I had the 5/8ths coolant hoses that attach to the water pump incorrectly fitted. One routes to the header tank through a T piece and the other to the heater core.
Have had no issues since I swapped them around.
Also due to the one liter plus expansion of the coolant when hot, I fitted an overflow / catch tank in he left hand tool box space below the a/c fan/condenser unit and a sight gauge on the tank. Makes life much easier.

 

[Peter Delaney]

I think there might be a bit of confusion creeping in here about the definitions of which tank is which.

Here in Oz, most people refer to the "HP tank / tube" as the "header tank/tube". This is the one that is in the main pressurised system & has the normal radiator pressure cap fitted. The level of the filler cap on this tank/tube MUST be above the highest water point in the rest of the system (the water temp sender holes on my Windsor with DC&O manifold). I put a small brass 1/4-turn tap into this hole/sender spigot so that air/steam can easily be bled off when the engine is hot - a length of plastic tube from the tap to the bottom of the chassis. For bleeding, I just run the engine up to temp, open the tap & wait till all the bubbles have gone. (I have a similar brass tap & plastic hose setup at the top of the radiator for similar purposes).

The other tank in the system is the "catch tank" or "expansion tank" - this is the one that is not under pressure, & feeds or receives coolant as things contract & expand. This is the one that I was referring to in my last post - suggesting that "bigger is better" & that about 3 litres should do the trick.

As to its location - my gut feel is that higher is probably better, but not really necessary (other than the filler cap).

The attached pic shows my setup - the header tube is on the left (with the filler cap about 1.5" higher than the highest water point in the rest of the system), & the expansion tank is on the right (it looks like it has a pressure cap on it, but the guts have been removed - it is just a lid).

The rubber tube from the HP header tank goes to a spigot on the bottom of the expansion tank, & the rubber tube from the top of the expansion tank is just an overflow to below the chassis.

I hope that this helps a bit.

Kind Regards,

Peter D.