Bubbly coolant- H/gasket??

[AxtellZ]

Hi all, this may get a bit rambly, but its Spring in NY (finally) and Z-fever is in full bloom!

Got out my 74 1/2 260, SU carbs-N36 intakes Thursday. In the fall, i had a coolant leak (very slight). The car has 2 coolant lines which run through the intakes, the line that went through the old carbs has been blocked off. I would notice the sickening sweet smell of hot antifreeze- seemed to weep from one of the front water hoses that go into the manifold, then ran along and dripped onto the exhaust manifold and/or exhaust pipe.

So, i got both water pipes from Courtesy, drove the car a bit, and it doesn't leak that i can find now! I changed the oil, it was perfect, no coolant at all. Radiator has no oil slick or anything- but if i let her run and warm up with the radiator cap off- it does have a "foam" like small air bubbles are mixing into the coolant somewhere...

I have not done a compression test, as i don't own the tester (yet), but i wonder if this is a sign of imminent head gasket failure, or if anyone has an opinion. The car is running really well, but i won't drive it if i have a failure waiting to happen:(

But there is the first car show of the season here on Sunday, so i'd like to go! Any and all comments, suggestions, or questions welcomed- Thanks everyone! JA

[2ManyZs]

It's pointing in the direction of a head gasket leak. Try having a pressure test done on the radiator and see if it is holding pressure. If it leaks down you know it's going somewhere. If it isn't leaking on the outside it's probably got a leak in the head gasket. :mad:

Most any garage should be able to do a pressure test on the radiator, then if it indicates a leak try the compression test. Sorry, wish I could give you better news.

[AxtellZ]

Now thats not what i wanted to hear Keith! Guess i'll take it to a shop since i don't have the tools yet. If'n i do need to change the head gasket, and was to pay someone to do it, any guesstimate as to cost or hourage? Fortunately i live in farm country where work is relatively cheap! Thanks, JA

[2ManyZs]

Well, bring it down here and I can do the compression test for you.

Time? Probably 4-6 hours, I guess working by myself changing a head gasket will pretty much kill an afternoon, if no studs break or anything out of the ordinary. Cost?? How much you willing to pay?:eek: Just remember the old saying, you get what you pay for. And make sure they have the right tools or the timing chain is going to cause a lot more work and expense.

Here I sat all week with no work, and I could have made some money.

[AxtellZ]

Hey- you know where i live....wife just "allocated" me $600 to pick up a 73 for parts or a racecar. Coulda been yours Keith! Thanks for the help:) JA

[2ManyZs]

Ya, but my tools and garage are here! Another Z? You trying to have more than me???

And it is warmer down here!

[Dan]

Hey 2Many just curious but why would a head gasket leak cause bubbles in the coolant did i misunderstand. I had a similar problem on my 72, the coolant lines that ran throught the intake manifold leaked bad so i just bloked them off and threw away the old lines. Since they actually warm the carbs not cool them i live in San Diego so no need. Also i thought 240's were the only early Z's to have the coolant running through the manifold am i wrong.

[59ghia]

Dan the engine block and head have water jackets,passages that

allow water to flow around the cylinder walls and up into the head around the combustion chamber. If the head gasket blows between the combustion chamber and a water jacket, on the compression stroke it blows the air into the water,bubbles. Kinda like a straw in water, when ya blow you get bubbles. Except its 160 or so psi through a small usually pin size hole,at first then it gets bigger.

Dave

[240znz]

Yep, it's a head gasket alright. Another place to check for foam is underneath the old cap. I think that this is one of the first places where it will show up.

Good luck changing that gasket.

Zed not Zee

[2ManyZs]

Well, 59ghia is right about how the head gasket leak can put air in the coolant system.

Dan, all the carburated Z's had coolant to the carbs or the intake to help with the cold start hesitation and warm up issues.

That being said, after I thought about it a while there are a couple other possibilities, they are a long shot, but still possible.

1. The radiator cap is not releasing the pressure build-up as the coolant gets hot and is forcing the air back into the system. This could cause the coolant to have a lot of bubbles in it. If the engine is not overheated and the radiator cap releases a lot of pressure when opened it is a possibility. I think the cap should be no more than an 13lb cap if I'm not mistaken, and I think the testing pressure is around 20-25lbs pressure.

2. It could be the water pump is cavitating and causing the coolant to froth, whether due to a bad impeller, or maybe the lower radiator hose is collapsing under load and causing the pump to be starved for coolant to pump. Thereby adding air pockets into the cooling system.

3. It may be the head gasket after all. It could be the head wasn't torqued down correctly and the gasket is blown (or about to). Or (let's hope not) the engine could have been overheated at one time or another and the head is warped just enough to let the compression blow the gasket. Usually if this happens you will see coolant running down the outside of the block, cause when the heads get warped they usually let a lot of coolant out, been there. Done that. :mad:

[AxtellZ]

well, its not leaking between head/block at all. I was all over with my flashlight, and can find absolutely no indication of a leak, past or present. The only indicator has been the frothy appearance with the rad cap off. Hopefully Saturday i can bend someone's arm & get the pressures tested. Assuming it is a pinhole pushing air through on compression, would a block sealer be a temporary fix so i can drive it to a shop (everything will be 20 miles plus..) I don't want to jimmy-rig it, but prevent any further damage. Thanks everyone, glad i'm here. JA

[2ManyZs]

I wouldn't put anything in it. If it is the headgasket you should be able to drive it 20 miles with no problem if you leave the radiator cap loose. That way it won't build up too much pressure and try to push any coolant out. Just leave it at the first detent and don't tighten it all the way.

BTW, I happened to see this in one of the old service manuals I have and thought it might add a little here.

Condition: Overflow loss, or poor circulation and overheating

Possible cause: Coolant foaming due to insufficient corrosion inhibitor

Correction: Flush and re-fill with new antifreeze.

Something else to think about.