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Old 01-23-2018, 07:33 PM   #1
Lee Mitch
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Default Help with radiator cap spray

I have had a reoccurring problem of spray coming under the radiator cap and decorating my hood. It occurs on longer pulls (up a hill) regardless of environmental ambient temperature. It does not occur with increased rpm. I have a moto-meter that works (tested it), and it indicates that my engine is not overheating.

The timing is dead on. I increase fuel and slightly retard spark when pulling a hill.

What gives? Where would you start? What would be other symptoms of a head gasket problem? Anyone think that could be it?

Thanks!
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Old 01-23-2018, 07:48 PM   #2
Bill G
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Default Re: Help with radiator cap spray

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I have had a reoccurring problem of spray coming under the radiator cap and decorating my hood. It occurs on longer pulls (up a hill) regardless of environmental ambient temperature. It does not occur with increased rpm. I have a moto-meter that works (tested it), and it indicates that my engine is not overheating.

The timing is dead on. I increase fuel and slightly retard spark when pulling a hill.

What gives? Where would you start? What would be other symptoms of a head gasket problem? Anyone think that could be it?

Thanks!
Make sure the radiator isn't brim full. Just fill to where the water or coolant is just covering the tubes by maybe 1/4 inch or so.

Same thing happens to me if I over fill it.
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Old 01-23-2018, 08:02 PM   #3
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Default Re: Help with radiator cap spray

As suggested ^ don't over fill the radiator. Make sure your gasket is good and in place and check your overflow tube. You could also be missing the baffle in the top tank.
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Old 01-23-2018, 08:15 PM   #4
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Default Re: Help with radiator cap spray

If the gasket under the cap is good you won't get any coolant out the cap. It would come out the overflow tube. Cap should be tightened snug on radiator neck. Is it the twist on cap or the threaded?
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Old 01-23-2018, 08:24 PM   #5
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Default Re: Help with radiator cap spray

As a general rule , the model A water pump over pumps Years ago , Snyders recommended grinding off the tips of the water pump impeller to reduce the pumping action I think that about 1/3 of each impeller tip is recommended . Snyders offeres a cut down impeller . It has worked real good for me . None of our model A's run hot !!! I also agree with post#2 . The motor meter and quail radiator caps are the very worst to leak . I used red high temp silicone sealer under the cap gaskets when I run thermo quail caps and it helped . It has been said that the new repro radiators don't flow as well as the original radiators . Its not likely that the head gasket is the problem . I would explore every avenue before considering removing the head . I've seen way too many head studs wrung off in the block .
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Old 01-23-2018, 08:25 PM   #6
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Default Re: Help with radiator cap spray

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Retorque your head just to make sure that is not your problem. Otherwise, you are making pockets of steam at the hot spots in your water jacket. Your radiator is somewhat plugged. You are overheating.
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Old 01-23-2018, 08:31 PM   #7
Lee Mitch
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Default Re: Help with radiator cap spray

Magicbox: Thanks. Definitely not full. It finds its own level below the top baffle.
Redmodelt: Thanks. Overflow tube clear! Gaskets.... Replaced them today. Will check if that's at least part of the issue when it stops raining here!
Eagle: I have the original cap (twist on) and a repop moto-meter. Allen wrench and twist top.

All: I have wondered if the gasket issue isn't sort of covering up an underlying problem. Or, do all radiators make spray, it just goes down the overfill tube?

Thanks again!
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Old 01-23-2018, 08:41 PM   #8
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Default Re: Help with radiator cap spray

Do you have a “locking” cap?

My meter qual cap was spitting on the windshield on longer straights above 40. The gasket under the base was shot.
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Old 01-23-2018, 08:43 PM   #9
Lee Mitch
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Default Re: Help with radiator cap spray

Purdy and Jackson: Original radiator, but completely re-cored with extra tubes. Only a couple thousand miles on it. I have always run a mixture of antifreeze and water so I don't believe it is rust/plugging issue. The completely rebuilt engine has less than 5000 miles. I will again re-torque the head. I had done that a bunch of times though, and the last couple I didn't get any more on them.

Purdy: I have enjoyed your posts over the years. Thx for a response. I have heard of the water pump fins being ground. I did not do that. It is a leakless from Snyders. I have always been suspicious of this though. Is it possible that the fins are only an issue when pulling a hill and not at higher rpm or at any other time? My common sense says "no", but as Samuel Clement said "Common sense isn't so common anymore"!

Thanks! Keep it comin'!
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Old 01-23-2018, 08:44 PM   #10
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Default Re: Help with radiator cap spray

If all else fails, have your radiator rodded out to get maximum flow
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Old 01-23-2018, 08:45 PM   #11
Lee Mitch
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Default Re: Help with radiator cap spray

Replaced that today! Will try it when the rain subsides to less than Hurricane levels around here!
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Old 01-23-2018, 08:45 PM   #12
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Default Re: Help with radiator cap spray

I agree with Jackson. Re-torque your head. It won't hurt a thing to do so. You can not torque your head too many times... you can only torque it too much. Keep it at 55 lbs.

Even if your head does happen to be leaking your radiator cap should seal tight enough not to allow water to escape. It should only go out the overflow tube. At a minimum you've got a radiator cap gasket seal issue. Perhaps cutting an additional gasket out of a thinner material to supplement the gasket already in place. There are different thicknesses of cork gasket material available at most auto parts stores.
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Old 01-23-2018, 09:42 PM   #13
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Default Re: Help with radiator cap spray

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I agree with Jackson. Re-torque your head. It won't hurt a thing to do so. You can not torque your head too many times... you can only torque it too much. Keep it at 55 lbs.

Even if your head does happen to be leaking your radiator cap should seal tight enough not to allow water to escape. It should only go out the overflow tube. At a minimum you've got a radiator cap gasket seal issue. Perhaps cutting an additional gasket out of a thinner material to supplement the gasket already in place. There are different thicknesses of cork gasket material available at most auto parts stores.
I agree as well.

its not an impeller issue - if it was sitting in neutral and revving the engine would cause it to spray - it needs the extra load (creates heat and pressure building) to blast into the water jacket to spurt out as your experiencing.

since you have a re-cored radiator unless its plugged up again with debris breaking free from the block id say you got a head sealing issue.

Yes if the radiator is plumb full it will come out and find its own level BUT it should for sure cover the tubes.

Check head nut torque to make sure its to spec and if you did have to snug a few up give it another drive and see what she does.

IF it still does it the easy way to find out is to get the engine warm, then do a leak down test with the radiator cap off. I bet it will behave like a geyser when you find the leaky offender cyl.
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Old 01-23-2018, 10:24 PM   #14
Lee Mitch
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Default Re: Help with radiator cap spray

Cross-cut: Great info. I did just as you suggested, but have not tested it yet (extra gaskets).

Sea-slugs: The top baffle covers everything. Darned if I know how much water is in there. If I fill it to where I can see it (baffle), it definitely will spray out! How should I determine the level? Leak-down. I have seen that term used here on FB before, but don't know what it is. I will do some research and give it a try. Thank you!!
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Old 01-23-2018, 10:31 PM   #15
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Default Re: Help with radiator cap spray

If it's a leaky head gasket, there will be combustion gasses in the radiator. It's easy to test. Auto Zone and O'Reilly's tool loan program includes this tester. You just buy the test fluid and the tester use is free if you return it unbroken.
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Old 01-23-2018, 10:34 PM   #16
Lee Mitch
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Default Re: Help with radiator cap spray

Thanks 40 Deluxe. Good to know. Sounds like a good test even if I wasn't having this problem. btw Kuna is a great place!
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Old 01-23-2018, 10:59 PM   #17
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Default Re: Help with radiator cap spray

I have a Motometer with wings below. The same thing happened to me on a hill with a long grade. After I reached the top, I pulled over to the side of the road and found that the cap was loose and I had to put in about a gallon of water.

We had gone to a car show in the morning. Before we left the show I check the water level in the radiator and it was ok. I used the wings to tighten the cap and I must not have tightened the cap properly. I had no problem driving on level roads, but about half way up the grade at 40 mph it started spraying water on the hood and windshield.

I bought a new seal and I'll make sure the cap is tight from now on.

David Serrano
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Old 01-23-2018, 11:30 PM   #18
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Default Re: Help with radiator cap spray

if the allen screws are overtightened it is possible to distort the rediator neck so that the gasket surface is distorted making it hard for the gasket to seal
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Old 01-24-2018, 01:54 AM   #19
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Default Re: Help with radiator cap spray

A friend had a similar problem. It only sprayed only while climbing up a hill and "pouring the coals to it". It was the water pump; somehow it would suck air through the shaft and only when stressed. No leaks on the straight and level. Go figure??
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Old 01-24-2018, 03:39 AM   #20
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Default Re: Help with radiator cap spray

Put on a stock cap & see what happens. "Some" radiator gimmicks are more trouble than they're worth!!!---Why risk ruining an engine, just for LOOKS???
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