Radiator cap spitting at higher speed

[lpl87]

I thought I would be smart & added distilled water to my radiator. It keeps spitting out the cap & it looks like rain om my windshield. I have checked to overflow tube & it is clear. The water level now is below the baffles but it still spits. What am I doing wrong ??

[tbirdtbird]

I would be suspect of the gasket on the cap

[lpl87]

Have looked at it and the o ring looks good. I put some vasoline on it but nothing else. Is there another gasket & how do I get to it ?
What level should the water be ?

[DaWizard]

Oh geez, where to start. Well, the water should just be over the top of the baffle. Second, there shouldn't be any hole in the cap for it to spit out of. The cap with a hole is for gas. Adding water should not normally cause the overflow of water unless you have it too full. So, on MY '28 Tudor I stuck a drywall screw into the overflow tube, it still allows for the overflow of over heating, but doesn't allow for the spitting out of water due to the splash.

IF you can safely, without breaking anything, Ford recommended in the Service Bulletins to move the opening of the overflow tube to the REAR of the filler neck. I have found that you can also use a piece of rubber hose to bring the top of the overflow tube up into the cap as high as possible. Both of these will work well to slow the spitting out of the water. I still like the idea of the screw in the pipe.

I have also inserted a bent piece of tubing into the overflow tub and redirected it to the rear of the opening without bending the existing tube, but this was done on one that the top of the overflow tube was about an inch deep into the radiator. (brass tubing can be found at your local hobby store, they make them in so many different sizes one will fit.)

So, unless you are overheating, you shouldn't be spitting anything out of the radiator. It will find it's own level and pretty much stay there.

J.C.

[tbirdtbird]

does the cap bottom out before the o-ring makes a good seal......try thicker o-ring?
O-rings do get chewed up. Did not know an o-ring was used there

[lpl87]

Will try a thicker o-ring. I don't think it bottoms out so that might be the problem.

[DaWizard]

What year is this on?

[lpl87]

1930 coupe

[BILL WILLIAMSON]

Forget this & that kinds of radiator cap ornaments & just use STOCK caps.
Bill Beenthere

[lpl87]

It came with a quail cap on it & was working fine until I added too much water.

[DaWizard]

I am thinking that should be a flat cork gasket in there unless it is an aftermarket cap.

BTW, I forgot to give credit, the "roofing Nail-Drywall Screw" is the idea of the one and only (thank God) Bill Williamson, I just pilfered for my usage!

J.C.

[lpl87]

If there is how do I get it apart to replace ??

[Mitch]

I keep the coolant level right at the baffle plate... Is it leaking from where the cap mounts to the rad neck or from where the cap opens

[lpl87]

Leaking where the cap opens but only at higher speeds.

[Mitch]

Well the cap should not leak period!!! if anything it would come out the over flow... I have these o ring kits from HF harbor freight and one of these sizes works great on the cap.. I forget which one but it's the blue metric box.
I use them on my motor-meters

[lpl87]

OK will pick 1 up next week. I didn't think it should leak either but it does. Looks like rain on the windshield but is harder to get off.

[John samp]

i had same problem after chasing it, i found out my radiator wasn't up to par, took in to have it dipped and found out it was a older one that somebody replaced, it did not have to 90 93 tubes, it only had 60 it was clogged even though when i did a flow test was okay, as i drove it would spit out of the cap, like it was raining, so had it re cored and my tanks were good, so he did heavy duty, and like 90 to 93 tubes, then when i put it back in i added a temp gauge, and have had no problems spiting out the cap anymore, be worth it to add the temp gauge and see what the cars running at especially when shes spitting, thiers many reasons for the spitting but know the engine temp before you start chasing ghosts like i did for a couple months.

[DaWizard]

Hey John samp, WELCOME to the VFF !!

[Mitch]

John as you found out the flow test is just a myth.
Welcome

[dmdeaton]

Instead of starting a new thread I will ask it here, related. Don't want to destroy anything yet. Roadster was spitting a little coolant from overflow while pulling into garage from last run. How do you remove the radiator cap? Does the cap unscrew? Why is there a hinge on the backside? Sorry bout the dumb question, I don't want to torque anything.

[Michael M]

Turn the cap a quarter turn counter clockwise and flip it back on the hinge. Look inside and you'll see the Allen screws that hold the assembly to the neck.

Here's what you'll need:

https://www.brattons.com/locking-radiator-cap-repair-kit.html

[dmdeaton]

Thanks Michael, I just needed to open it to check the coolant. It took about half a gallon to bring it above the baffle cold. I didn't know how to open the dang thing. Thanks for the link also.

[Nabco]

Had the same problem last weekend driving to a car show, thought it was raining but the sky was clear, I have a quail cap and it was not 100% closed, it was only open a hair but it was enough, closed it and solved the problem.

[CarlG]

I posted this elsewhere here, but it fits this thread:


If you have a "leaky" quail or other flip top radiator cap, try putting one of the steel washers meant for the gas gauge under the "rubber" gasket and hold everything in place with a slight smearing of silicon sealant. That adds just enough height to make it not leak.

[Mitch]

I believe the OP said the leak was from the top seal and not where it mounts to the neck

[CarlG]

That's where my suggestion in post #21 comes into play.

[BILL WILLIAMSON]

When Chief was breaking in a NEW engine, he would use a spare '29 GAS cap, with the tiny vent hole, to let him know if it got TOO WARM!
Chiefs' Son