The Stovebolt Site Forums The Shop Area Engine Shop foaming antifreeze

ive got trouble with the antifreeze foaming and coming out the overflow. what causes this? Also have you ever seen a radiator without a drain valve? Cannot find one. The overflow is a problem. Any help is appreciated. Thanks

Sorry to be the bearer of bad news . . . hopefully you blew a head gasket, more likely you have a crack in the head and combustion gasses are leaking into the water jacket and causing the foaming. You might run a compression/leak down test with the radiator cap off and watch for bubbles.

Don't know if you have an automatic tranny or not, but if the tranny cooler in the radiator springs a leak, it will do this also----but more likely a gasket or cracked head. Has it overheated with you lately?

You dont say what engine u have, I hope its a head gasket or bizarre radiator situation, but I suspect the most likely problem is craked head. If so pay attention to ur oil and dont run it if the oil gets creamy. U could end up with even worse probs.

Yup, Yup, Yup, your gasket do be blown. I have had 2 similar problems. One I fixed by retourquing the head bolts (1966 Pontiac OHC 6). Its worth a try, doesnt cost anything but your time.

If you have Mountain Dew in your radiator instead of antifreeze, that could make it foam, too

I've got a 350 with auto trans. No water in oil. And it has a trans cooler on it.

Do a compression test on each cylinder and apply air pressure to each cylinder. If compression test is about normal on each cylinder and you get bubbles on a certain cylinder when you apply pressure you more than likely have a cracked head. You didn't say what year 350 it is. If it is an orange engine made in the 70's or before the heads usually stood up pretty good but the newer heads are lighter and have a history of cracking.

If 2 cylinders show a distinct presure drop you may have lucked out and blew a gasket.

Heads still not to big a problem. 350 heads (or whole engines for that matter) are pretty cheap and easy to get ahold of.

The engine is from the late 70's not exactly sure. The truck has not overheated with me. Ran compression check high 120 low 110 with no leak down. All cylinders pretty consistant. Its a 350 corvette motor with 350 auto trans. I brought it to a mechanic while it was doing its deed showed him my compression readings and he said that they looked ok to him. He told me to try a new radiator cap and go from there. Could this cause a problem? Also bought a new set of guages fixing to go hook them up and watch the temp. Dont trust the original. Thanks for the input men I appreciate it.

Since you haven't found anything else so far, I still suspect the transmission cooler leaking in the radiator. You could drain and refill the radiator, then remove and tie the cooler lines together temporarily with hose. Drive it a few miles and see if foaming reappears. Also, is the fluid level of the transmission ok? I didn't just dream this up--I've seen it happen several times.

Thank you smitty, dont know much about the cooler in the radiator but it does have an add on cooler underneath the radiator will check that out in the morn. Thanks again.

Is the coolant in the radiator oily??

How old is the waterpump?

how long ago was the thermostat changed?

58: Find a NEW mechanic! :p You do not have near enough compression pressure! You said 120's down to 110. The medium compression model 350, and the high compression 350 Corvette engines should be in the range of 145/150 minimum! Thats with the medium engine (9.5 to 1), and the high (10.25) compression ratios. The 10.25 engine, new, will run about 165.

Was your engine up to operating temp when you did the comp test. If the engine was not hot enough, it will yield false/low readings because of the piston rings lack of expansion, and piston to cylinder fit. Need to start and run that engine until its good and hot, then re-test compression. You either did not test correctly, or you have no rings or valves left!

If your re-test shows low pressure between any two cylinders, you found it. May be a headgasket. May also be cracked head, usually in the exhaust seat area. This is more likely than the head/block gasket area. SBC heads will crack at or just below the valve seat. Usually what causes this is worn valveguide and the the valve head distorts/bends on the seat and will not seal which will cause a hot spot on the seat at blow-through area. Cylinder leakdown test will verify.

Also try vacuum test. Watch the action of the needle, if bouncing or jerky motion indicates valve trouble, either bent/sticking. You engine may seem to run OK, but a valve may not be sealing, or is toasted!

An easy test to make, to find out if the bubbles in fact are coming from your block, and not your radiator is this, Pre heat engine to operating temp, then pull water pump belt, thermostat housing and thermostat. Replace housing only. Then fill to neck. Start engine, rev, release, rev, release, and watch for bubbles in neck. With engine hot and cracks expanded will show bubbles.
If a headgasket leak, the bubbles will follow the rev/release pattern. If you experience a rapid rise in coolant level, you have a big crack in the seat area and exhaust gas is venting to the coolant. Spray light 10W oil into sparkplug hole of any suspect cylinder and you will get smoke bubbles, to verify which cylinder/seat is leaking. You will have to work kind of fast as your engine will get hot after 2 or 3 minutes.

Sometimes a compression test will not show that low a reading on a cracked head, and sometimes it will, just depends on where the crack exactly is and how big it is. Little hairline crack will/may show with a leakdown test and may not show with a compression test. Hope this helps!

Think Chevy!

Coolant is in radiator only, have no idea how old water pump is. and will change thermostat this morn. Engine was not to full operating temp due to fear of burns. I was just trying to see if there was a major difference in comp on any two adjacent cylinders or if I could see compression loss on the guage. If it were a blown head gasket why didn't the guage indicate that? Could a cracked intake cause this?

Found the water neck leaking and no thermostat. Replaced old antifreeze fixed leak and added a 195 deg. thermostat. Antifreeze stopped foaming now it is just pushing straight antifreeze through the over flow and it seemed to heat up to a higher temp quicker than normal shut it down and think I will change the water pump tomorrow. I guess I'll hook up the new temp guage I bought so I can monitor it closer. Also didn't notice any bubbling with the radiator cap off.