hi guys, many times already did i post something regarding my slight heating problem on my 69 302.
i got the fan shroud and it seems better, but then again, it got a bit colder here too so nothing conclusive. took it to the shop today to have it chemicaly tested on a blown head gasket: the fluid didn't respond to co-gas in the cooling system, but we also tested the temperature of the water with the cap off, and then we saw that it bubbles slightly and keeps on doing so, even on operating temperature. so the guys from the shop seems to think that i might have a very slight crack in a cylinder head, that opens up/ gets wider when the block is at temperature, causing even more heat build up so that the system can't get rid of the heat quick enough and eventually blows out...

anyone have some experience with this? cause i got two options i guess, either i take the heads off and have 'em done and tested for cracks, OR i try one final thing and get myself a high performance waterpump and see what happens with that first.

i suppose the waterpump wouldn't hurt anyway, but if these symptoms ring a bell with anyone i might as well get it over with right away and strip the heads.

thx already in advance...

 

The bubbles are caused by air being in the system. Keep the cap off for a long time and let it burp. If you have a cracked head, then water will get into your pistons and cause white smoke to emit out of your exhaust.

 

We do chemical tests in my shop pretty regularly. I find them to be very reliable. Even with a very slight head gasket leak, the test always shows positive.

 

hmmm, indeed no white smoke, but on the other hand soaring, the system shouldn't have any more air in it because i got rid of all the air upon filling it up, venting air from every possible hole i could open starting from the lowest to the highest point, and in the shop we left it for about half an hour, and i saw no change in the amount of bubbles. but i am talking about little bubbles here, the size of bubbles in sparkling water, to give you an idea... and so they keep popping up with a few seconds between them. could it be that there is a small hotspot somewhere in the block, that is causing these tiny bubbles? anyway, i'm glad 69FE has a lot of experience with chemical tests, that way at least i know they're reliable.

if it's not a cracked or warped head, and i don't think that it's still air from the system, then what else (if anything) could it be? i suppose i'll start with the pump then and check again afterwards. hopefully that 'll do the trick....

 

If the water pump is working, then you will see the water rolling in the radiator with the cap off and the engine up to temp. Take the thermostat out first so you can see the water rolling in the rad before it reaches operating temp. I forget about what radiator you have and what fan you have. Run that by again.

 

the thermostat is out already, and still heating up slowly apparently.

so the setup coolingwise is now:

24" 3 row original but remanufactured rad
fan shroud
6 blade flex a lite fan wich adjusts to rpm
stock pump
15 psi cap
30 percent antifreeze 70 percent H20


must say the shroud helps a little though, better then it was....

 

Just out of curiosity, what type of temperature gauge are you running?

 

Put a 13 pound rad cap on it with a recovery tank. Jerry brings up a good point. Are you sure your temp gauge is correct?

 

the one in the dash for the moment, but the test in the shop was done with a mechanical one, the type with a dial indicator: it showed about 80-90 degrees centigrade with the cap off and as the temperature rose so did the dash gauge accordingly. so my guess is, when it says overheating it's more or less reliable... and the sender was changd three weeks ago, started off with that first.

but for a recovery tank, is that a special cap that comes with it? i.e with a cap that allows to flow coolant back into the rad after purging it out?
and maybe this is a stupid question but wouldn't that be a temporary solution and not a fix of the actual problem, or can i drive it for ever with that?

thx already for your time, always grateful for your input guys..

 

The recovery tank captures any fluid that spews out from underdeath the 13 pound cap, then replaces it in the rad after it cools down. That way, you know you have enough fluid in the rad at start-up.