Water hammer? Or what is it?

68conv4sp · Mar 29, 2008

There is an irregular tapping sound at the thermostat housing. I have tried several types and temps of stats and replaced the water pump. When I run without a stat the sound is gone. I have confirmed that the stats are squezzed between the housing cut out and the intake surface. I am out of ideas.

mrmustangman357 · Mar 29, 2008

maybe the thermostat is loose in the housing. use some rtv around the thermostat when you install it and make sure it dries completely before filling it up

JDS68Stang · Mar 29, 2008

Pull out the stat again, drop 2 aspirins under the stat in the block and reinstall, its most likely air trapped and I heard stat won't open w/ the air trapped under it and it will make that noise.
Just read about the same problem on a vette forum and this was the solution recommended to get the air out, worth a try.

68conv4sp · Mar 29, 2008

I thought that either air was trapped or the stat was loose. So as an experiment, I drilled a 1/8 hole on the side of the stat plate and used RTV to glue the stat in place (very tight anyway in the housing) and let it dry for a day before adding water. Still makes the light hammering noise. Any other ideas?

68conv4sp · Mar 29, 2008

By the way, I can feel the pulse in the hose when each click happens. It is not in time with the motor RPM. So, to summarize: new water pump, new stat (RTV used to hold stat tight), bypass hose is clear, and it still clicks/hammers. It does not happen when I run without a stat. So frustrating.

chromedog · Mar 29, 2008

some people drill the hole to let trapped air past the t-stat, and into the radiator. if you do this, the hole should be at the 12 o'clock position...

68conv4sp · Mar 29, 2008

I did that w/ a 1/8 inch hole at the 12 o'clock position. Still clicks/hammers. Thanks for the thought.

gtss · Mar 30, 2008

One other possibility is the coolant actually boiling, perculating(sp) in the system I have seen it happen in other applications,
then it creates a sound like Mom's old coffee maker

which means somewhere in the system it is too hot. coolant strength?, flow?
not enough pressure?

looking at the pictures on your car domain site, is the water pump pulley too large
causing it to turn to slowly? is it the correct rotation water pump?

sorry but more questions than answers?

gtss

68conv4sp · Mar 30, 2008

I can answer some of them. The coolant is distilled water with 30% Prestone and Water Wetter. The rad cap is 14 lbs. and the hoses are firm when hot, indicating pressure. The car does not overheat, so I beleive the new water pump is providing flow. I don't have a car domain site that I know of.

chromedog · Mar 30, 2008

are you looking at my cardomain page? no cooling issues with my car...(frpp waterpump, cheapo flex fan, northern aluminum radiator with no shroud)

mustangman1974 · Mar 30, 2008

are you using a mechanical fuel pump. I have an issue with the eccentric and came bolt workign its way loose and it sounded like a thermo ticking.

gtss · Mar 30, 2008

oops
I must have looked at chromedogs pictures, so ignore the comment on the water pump pulley
I still would be suspect of hotspots somewhere, but that doesn't necessarily mean over heating in general
gtss

if I am reading your info correctly, yours is a 68 block, edelbrock heads,
did you drill the holes in the block for vapor escape????
I forget the term they use to describe them but that might explain vapor or air causing the thermostat popping
gtss

68conv4sp · Mar 31, 2008

What is confusing to me is why it does not click/hammer without the thermostat. Even though the thermostat is VERY tight in the housing.

65fastbackresto · Mar 31, 2008

gtss may be on to something

I`ve got the old style block with edelbrock heads, and they didnt drill the steam holes in my block to match the heads, and my thermostat hammers some too, not all the time, but on and off, enough to make ya think your crazy.

I bought one of those stethoscope setups at Sears to track down stuff like this, pretty handy little tool.

68conv4sp · Mar 31, 2008

Good to hear that someone else has heard this. I thought I was unique AND crazy. Is yours audible at idle only or could your hear it with the stethoscope above idle?

65fastbackresto · Mar 31, 2008

Pretty much at idle when its warming up

seems to quiet down after its warm, yours do that too? Dont need the stethoscope to hear this, it sounds like a lifter clanging, but it aint.

To be honest, I haven`t put the stethoscope on it, but I put it on everything else in the engine bay trying to find the sound to no avail, and when you put your post up........it became painfully obvious that I`d missed something.

I never would have checked the therm housing, but I`m going to tonight, it has to be that though, I`ve tried everything else.

JDS68Stang · Mar 31, 2008

68conv4sp said:
I can answer some of them. The coolant is distilled water with 30% Prestone and Water Wetter........

You might want to read BTJUSTICE's posts on this link and loose that Prestone in a hurry, its a Dex-Cool clone. GM just lost a lawsuit over it in Cali. on 3/20/08 and has to pay out. Mostly this stuff eats nylon/silicone gaskets which GM used in a lot of their vehicles, but not all.

If you get any air in your system w/ Dex or its clone Prestone count on trouble down the road. Here's the link to his posts, he recommends Zerex green or Zerex G-05 which hasn't shown any problems like the Dex has.
http://forums.stangnet.com/showthread.php?t=724848&highlight=btjustice

Your sure you have the stat in correct right?, 65resto may have a good point if you have an aftermarket manifold/heads.

68conv4sp · Mar 31, 2008

I have avoided the question of drillied steam holes in the block since I do not know if that was done. I doubt it. So, if that was not done, then those pockets could get very hot and boil. Presumably that is the theory for the clicking/hammering source - as the gas bubbles expand and contract the pessure waves hit the thermostat almost like a speaker? Good thing I love that car.

65fastbackresto · Mar 31, 2008

Try this, a buddy suggested that I should

good way to tell if you have hot spots. Take a heat gun and take some readings on front and back of heads. Go flog your car a little bit, and do it again, if you have alot higher temp in back, you probably need the steam holes.

We gonna try mine in a few weeks, I`m still getting the bugs outta mine, got like 100 miles on it so far since redone and I`m still tweaking on it.

I`ve got an email from an edelbrock tech I can forward you on the subject if you think you may need it.

And yea I think your right on the sounding thru the thermostat.

bnickel · Apr 1, 2008

i used to get that thumping sound like that on my car and it was due to the lever vent radiator cap i was using. not sure why but when i swapped th cap out for a regular unit the thumping went away. something to consider if you're using the lever vent cap anyway.

Water hammer? Or what is it?

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