got a 1970 307 in my hotrod....supposedly 23,000 miles...the motor is clean inside..the delivery has been sitting in my garage up on jack stands for 6 years due to my health..this summer i finially got it runnin'..ive always had some moisture from the exhaust....no white smoke....recently when i get back from a cruise,i heard a couple a thumps..this happened several times..when id get out ,it already stopped..the temp is always below 180 ..i recently installed a champion 3 row core radiator,16lb cap,new hoses and a 180 t-stat..i replaced the water pump a couple a years ago..there is no milky oil,no overheating..i also installed a pusher electric fan,to work with the motor fan..im a retired ase mechanic and think its a headgasket..i installed a stant radiator pressure tester and after runnin' a bit ,the needle was pegged...not what i wanted to see..what do you guy's and gals think//
yea i would of done that,but dont have the kit..the only time ive seen pressure build like that wash either a head gasket or crack (god forbid)...
1.Pull all the sparks plugs 2.Pressurize cooling system with a cooling system pressure tester & let it sit for awhile. 3.Spin the motor with a remote button & watch for coolant from any of the cylinders (might have to do this when it's been warmed up) Good luck
don,the only coolant loss so far seems tobe from the coolant recovery tank..im thinkin from when the press builds..you also cant smell antifreeze in the exhaust..i have yet to see the upper rad tank empty.........................fuel,.....yea i might have to check the cyl.s for coolant..the couple times i had the plugs out prior,ive never noticed any white plugs..
If the suggested tests show nothin', I'd be inclined to add a block-saver product to the coolant and keep an eye on it. Good things, it doesn't overheat and you're not passing coolant into the oil. Bob
You absolutely have to lose the pusher electric fan working with the engine fan. If there is a cooling issue with the engine fan alone, it must be addressed, and NOT band-aided. A leak-down test can also confirm the head gasket or not issue, as well as the other good suggestions already offered, all the best. TR
I am not sure about the pressure in the rad, it sure sounds like a busted head gasket. The thumps could just be an air bubble working its way out of the cooling system. Is your rad tank or cap below your engine? It could just be trying to burp itself. Have you fired it with the engine cold and the cap off? if you have a busted head gasket leaking into the cooling system it should blow water all over the place cold. I assume it is not cross fireing? like a leak between the cylinders?
Testing for combustion gasses is as easy as can be. Your engine will build pressure , the stant tester should be used to pressurize your cooling system to see if it will hold 15 psi , NOT to see if your cooling system builds pressure. Tests caps too see if they hold 15 and blow off above. Pressurize your system and remove the plugs. Let this set for 1/2 hr or until it drops pressure, if it drops quickly you'll soon find the problem. Now crank the engine with plugs out. Get coolant out the plug hole , well there's your problem.
31 vicky....i know the cooling system builds pressure,but it shouldnt peg the pressure guage should it?ill have to pull the plugs and pressurize the cooling system and check for coolant..........pork...the rad tank and cap are above the engine level......traditions....the temp runs no higher than 170-180...the electric fan is thermostaticly controlled...the engine fan is a alum. flex and has no shroud..ive already checked rads with the stant hooked up and alot never pegged the guage..headgasket problems did
Maybe so, but that's not a definitive test or conclusion. Its certainly suspicious and such findings would warrant a combustion gas detection test for sure. No way would I change gaskets based on your explanation of the method you used . Now if you do determine your heads need to come off, a set of 305 heads really wake things up on a 307. Steel shim gaskets are available thru felpro so the quench remains around 0.04.
31 vicky....pressurized the rad,let it sit..no water in the cylinders...did a leak down testthe guage fluctuated from 20-35 on all cyls..felt pressure commin' from breather..motor doesnt burn oil tho..oil pan leaks..found the noise was in the upper hose(u could feel it)and here it,like the t stat was makin noise..while runnin' to get hot there was water at the tailpipes again..didnt smell or look like coolant..the noise when it happens,is when i shut the engine off(has tobe warm enough),looks like the t-stat was open,then i shut it off..soon it make 2 clangs,thuds and that is it..i replaced the t-stat and now have bad threads in my trips intake..soooo itll be on hold awhile..
Helicoils will save that intake. The 2 x 4 intake on my 27 is an old Offy and one of the thermostat housing bolt holes got bad. I simply helicoiled that one hole and it actually clamps tighter than the other hole now. Napa sells a kit just tell them what bolt size you are trying to do. Don
I had a bad t-stat making thunks like that in my pick up. Pulled it out on the road, problem solved. As far as testing for a head gasket leak thats easy. One reason that pulling your plugs WON'T work for finding all but the worst headgasket leaks is that your cooling system runs at 15 pounds+/-, but your cylinders run at 125PSI during cranking, more when running. 125 pounds will push a lot more air through a small hle that 16 pounds will push water the other way. Now to finish the diagnosis just pop the hood, pull the rad cap, start the car and let it idle (or bump it up on the fast idle cam. Then top up the coolant to the very top of the filler neck. If you have a head gasket leak you will start seeing bubbles burping up in the radiator neck. A few random bubbles while it is warming up are okay. Head gasket leak bubbles are consistent.
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