Loss of Coolant and Running Hot - Cure

This past weekend was a blast sorting out my GT-40. After a number of drives I ran into an overheating issue that appeared as follows:

1. The raidiator was cool - but the temp gauge was reading hot.
2. Would get boil over at the cap.

First thought - bad thermostate. Replaced that - with the help of Eric and Ralph (thank you guys made it much more fun). Seemed good. Went for another drive - everything seemed fine. Eric was following - when i got on the throttle he indicated that it seemed like mist was coming out of the exhaust. The car continued to run fine - then about 10 minutes later started heating up again - i pulled over - had overflow at the header cap - and again a cool radiator.

At this point i was worried about a blown head gasket - but the engine was running great.

After it cooled, refilled the head tank and started up again it warmed up fine - radiator was hot, and the temp was stable.

I had the engine cover up, and hit the throttle a few times - then i noticed steam from the engine compartment - seemed that everytime i hit the throttle - water would overflow at the radiator cap. So, first thought - bad radiator cap - replaced that - no change - same issue.

Then the thought came to me that the header was connected to the high pressure side of the cooling system - and when the engine was reved up it would cause the overflow.

I read through this forum -found another thread that this was the issue.

I reversed the hoses that connected between the pump and the outlet - and as of now it looks like that may have been the fix.

I will keep you updated - if anyone else is running into a similar issue i will be glad to share any other information i may get.

Keeping my fingers crossed that this is the issue.

Between this issue, and the fact that the disc brakes still have paper on the inside of the disk area below where the pads hit, i do not think the prior owner drove this at all. Hopefully i will have it sorted out soon and be able to put a few miles on.

Thanks again for everyone who has contributed to the forum - the information was really helpful. And again thanks Eric and Ralph for stopping by and giving a hand and great advice on Saturday.

Regards,

Jesse

Presumably your engine is in a nose down position

Very often this causes an air bubble at rear of heads / manifold.
this causes a hot spot and then steam pockets that cause coolant to pressurise.

Blead hose from a tapped section at back of manifold is the permanent fix

Quick fix is jack front of car 2 foot up when filling and bled ing the system to clear any air

Ian

I had a very similar problem- ran fine, boiled at other times, air collected in rad had to be bled, spent a lot of time worrying, watching the temp needle with some runs fine and then... had a good few weeks of everything smelling of glycol.

Was told to run a line back from the rad top to the header tank, get a larger header/expansion tank, put a heavier cap on the tank (original 15 psi I think-18/20 suggested), and run a small bore hose from the bleed on the top of the block to the header tank as well.

Seemed to me a big job/pain to run the rad bleed line back so did a larger header/expansion tank and ran the line off the top of the block to the new tank (a 4mm internal diameter hose so as not to make it the preferred route for the coolant) and kept the old pressure cap and now everything seems to be very happy. I have put 750 miles on it since then and not a touch of air in the system that has not bled, temp sorted, nervous wonderings have settled down, and now driving without worry. Happy, happy, joy joy!

hope that helps. cheers al

Hi Jesse,

Glad you had some helping hands, does make it less daunting for sure.

The biggest challenge is to make sure ALL the air is out of the system. It's best to have the heater control valve propped open while filling the system. Also during the initial warmup turning on the heater temp control and heater fan on will help move the air out of the heater core.

We actually fit a filler connection on the heater hose accessable under the cowl fuse panel cover. That way you can confirm the heater is purged. Also on some early cars the heater is higher than the thermostat housing, header tank and rad (of course). So make sure you get all the air out.

If there is no overflow tank connected to your header tank than you have to ad one, at least a quart, for expansion. The drain back (siphon hose) connects to the header tank filler neck. The hose should also reach the bottom of the overflow tank, when cold the hose must be submerged in coolant so it won't suck in air on next hot cycle.

Probably best to keep about two inches of air in the top of the header tank so the coolant has some room to grow before heading out the filler neck to the overflow tank.

There is one more nasty little secret, you must investigate: the lower rad hose entering the waterpump must be reinforced with an internal wire coil. Squeeze the hose when cold, if it's as soft as the upper rad hose there will be no coil in it.

The wire spiral prevents cavitation under acceleration. Sounds familiar eh?

When that happens the engine is starved for coolant when it needs it most, not only that, the waterpump aerates the coolant so whats gets through is full of bubbles, result: instant localized boiling in the heads and spectactular discharge of coolant.

Just a couple of things to check out then you will be good to go.

Cheers

Ian

IanAnderson said:

Presumably your engine is in a nose down position

Very often this causes an air bubble at rear of heads / manifold.
this causes a hot spot and then steam pockets that cause coolant to pressurise.

Blead hose from a tapped section at back of manifold is the permanent fix

Quick fix is jack front of car 2 foot up when filling and bled ing the system to clear any air

Ian

Click to expand...

Hi Ian,

Good suggestion for level to nose down engines. All CAVs are factory set nose up as in a Mustang or Cobra application, so that's not a contributing factor in this situation.

When it's left up to me the motor is level to .5 degree up, however we do steam passages on the back of the intake manifold to the front of the manifold just behind the thermostat housing, that lets the air escape.

Maybe we should post a "Top Ten List" of things to check over for new owners, could help dodge a few bullets on relatively minor issues... hmmmmm

Cheers

Great advice thanks, the car already has the bleed from the radiator. I live on a hill- so it will be easy to bleed out the rest of the sytem.

Any suggestions as to where i can get an expansion tank - i would like to get at least 2 qts and something that will look good - preferrably alunimum with site glass.

Thanks again,

jesse

Don't ignore the rear of the intake bleed lines. This may be a little work, but it is THE fix for this problem along with a bleed from the radiator. It is an automatic self air bleeding system, I did mine (GTD) and I NEVER think about air in the system anymore.

www.cantonracingproducts.com
I am using the 1 1/4 qt. tank on my roadster for expansion of the pressurized fluid and one of the non pressure tanks with the sight glass for a overflow reservoir. they are very well made and look good
www.cantonracingproducts.com

Lynn,

Thanks i just ordered one from canton - they look perfect for this application.

Regards,

Jesse

Ian:

Just curious: do they make a wire spiral insert or must the hose be ordered with it incorporated? The angles and larger opening on the pump end for that hose are unique and I really doubt a pre made hose with wire in place would be made for my application. Tell me I am wrong. . . . .

Chuck

Canuk40 said:

There is one more nasty little secret, you must investigate: the lower rad hose entering the waterpump must be reinforced with an internal wire coil. Squeeze the hose when cold, if it's as soft as the upper rad hose there will be no coil in it.

Click to expand...

Hi Chuck,

How's it going my friend. About the coil, I think you can buy it from Earls or XRP through any decent race car supply or hot rod shop. I have wound my own from stainless steel tig welding rod when in a pinch. So yes, you can fit it to what ever shaped hose you have

Cheers

Not sure what size they are but you could call them.

LOWER RADIATOR HOSE SPRING STAINLESS STEEL BIG BLOCK 1965-1973 - CJ Pony Parts, Inc.
http://www.cjponyparts.com/lower-radiator-hose-spring-stainless-steel-small-block-1965-1973/p/HW769/
Or you could spend $70 for a ford GT spring
Ford GT Radiator Hose Springs from Accufab 05-06

Canuk40 said:

I think you can buy it from Earls or XRP through any decent race car supply or hot rod shop.

Click to expand...

Yes, Summit Racing carries them from Earls, Russell, Fragola, Aeroquip up to AN-20 size (20/16 = 1.25"). The product category is "hose inner support spring".

Hose Inner Support Springs - SummitRacing.com

I took the car for a longer drive yesterday and had new Avons put on it.

After switching the bottom header hose from the high pressure outlet to the low pressure - everything is working perfectly.

The system already had a bleeder hose from the back of the manifold and from the top of the radiator - so i think it is automatically bleeding any air.

I say a definate on the top 10 list - checking to make sure that the bottom header tank hose is hooked to the intake of the water pump - rather than the thermostate output.

Thanks again everyone for the input.

Regards,

Jesse

So the PO (or builder) had water pumping into the bottom of the header tank? Wow.

Didn't someone way in the other thread that they'd seen your car at track events, etc.? Just makes me wonder how it got to this state (of affairs).

Alan,

I think the car was gone through with new paint and perhaps many upgrades - new brakes - these look like zero miles. I am guessing that they pulled the engine and when they replaced it they swapped the hoses. Since then they could have hardly driven it.

Clearly, since painting it has virtually no miles - not even a nick in the paint.

I have not noticed anyone saying it was at track events - but i did see someone say they knew the car.

That is about the only explaination that makes sense to me.

Jesse

Barrett-Jackson-GT-40 said:

Alan,

I think the car was gone through with new paint and perhaps many upgrades - new brakes - these look like zero miles. I am guessing that they pulled the engine and when they replaced it they swapped the hoses. Since then they could have hardly driven it.

Clearly, since painting it has virtually no miles - not even a nick in the paint.

I have not noticed anyone saying it was at track events - but i did see someone say they knew the car.

That is about the only explaination that makes sense to me.

Jesse

Click to expand...

On another tangent, the 'new' overheating problem might have been the straw that broke the camels back & helped them decide to sell, in which case depending on how you feel about what you paid for it, all works out in the end, just be thankfull you didnt 'have' to drive it interstate immediatly post auction.

Barrett-Jackson-GT-40 said:

I have not noticed anyone saying it was at track events

Click to expand...

Sorry, you're right. I was thinking of the blue one on ebay, not yours.

Jac Mac,

I was thinking the same thing that the seller may have let it go for less or decide to auction due to not sorting the issue out - that or just had not driven it hardly at all to even notice.

Just guessing.

But after taking it out again today - just loving the car.

Jesse

Canuk40 said:

Hi Chuck,

How's it going my friend. About the coil, I think you can buy it from Earls or XRP through any decent race car supply or hot rod shop. I have wound my own from stainless steel tig welding rod when in a pinch. So yes, you can fit it to what ever shaped hose you have

Cheers

Click to expand...

Thanks Ian.

Drove the GT couple of evenings ago around dusk. 90 degrees outside, but the AC made it tolerable. All was well. Water temp rock steady at 190 degrees. It was a great drive.

Punched it a few times after 20 miles or so. Nothing radical, but enough to get the RPM's up to 5 grand or so and feel the accleration. After about 20 miles of the temp holding rock steady at 190 it started climbing to about 220. After reading your post I am wondering if that lower radiator hose may have led to the cavitation and aeration of the coolant. Would this scenario be the consequence of not having that wire support in the lower hose???

If I understand the concept, the fact the GT has a very long plumbing system and the pump has to push / pull coolant such a long way may increase the cavitation / aeration problem as compared to a car that has the radiator six inches away from the water pump. Right????

Our recovery tank is typically about a third full. After a good run it is about two thirds full. After cooling down it is back to one third. So we are not losing any coolant.

Any thoughts????