LenWoodruff

Since my engine rebuild about 500 miles ago I have noticed after driving the overflow tank is full. It gurgles for awhile which I assume that it is going back into the radiator.

It has an aluminum radiator with a 15 lb cap and Edlebrock aluminum heads.

Today after coming back from a 30 minute drive and letting it set there was antifreeze over the garage floor.

The overflow tank was empty but the radiator was full.

The car never overheats and stays in the 160-200 degrees range when driving.

Any thoughts?

DUB

I would HIGHLY advise you on using a coolant system pressure tester and check to make sure your cooling system is sealed up. Pump it up to 15psi and make sure the needle does not drop for about 10-15 minutes. If it drops..that is telling you that your system is open.

And just becasue oyu ahve been running at 200 degrees and not over heating....it is becasue you ahve not got to the point where the cooling system is actually going down on coolant.

BUT...now that your over flow tank is DRY...that is telling me that you no longer have a reserve...and if you keep driving it...each time you will loose more coolant until one day it runs HOT.

DUB

LenWoodruff

So you think air is getting into the cooling system and causing the overflow to overflow?

HeadsU.P.

I suspect some air pockets are still in the system some where. The best and easiest way to burp a C3 is to put the front end up on ramps. I know you may not be too keen on crawling under the car, but then you can do a visual check on most of the hoses / clamps and check to see if there is a spring in the lower rad hose. With the Rad cap the highest point remove the cap and let the engine idle. Watch the bubbles appear at the filler neck and dissipate. I think once its burped, your troubles will go away.

LenWoodruff

So you think the gurgling is cause by air in the system?

The shop said that they vacuum the cooling system when they put the new engine in it. That should have removed the air correct?

Could there be another place for the air to enter the cooling system?

HeadsU.P.

Yes on the gurgling.

Vacuum? I have never heard of that.

I also suspect that there are not any holes drilled into the thermostat for a by-pass during warm-up.

If air can get into a coolant system, then coolant should be able to escape the same way, right?

It needs to be burped and you can not burp it on a hoist or on the level ground. The rad-cap / filler neck has to be highest point. (higher than the T-Stat-housing)

doorgunner

Turning on the heater to circulate coolant thru the core can help burp the system. I have spent an hour burping a SB and still had to add coolant a couple days later.

LenWoodruff

I think I will take a drive today with the heater on and see if it gurgles when I get back.

HeadsU.P.

H-m-m-m-m-m-m. Texas. Run heater. July. Been a pleasure knowing you.

The coolant system may not gurgle but you certainly will.

LenWoodruff

LOL. You northern guys are too much!

I have never had this problem before this engine rebuild. I thought it could be something with the aluminum heads that cause that.

I did buy a new overflow cap today. I will see if that makes a difference.

HeadsU.P.

Actually, the shiny style heads dissipate heat much better than the boat anchor ones. However, with any head, if a water passage ability is questionable then you have troubles. But that's pretty rare.

Also, it seems like some of those Rad Caps don't fit like the original ones especially with the aftermarket units. Either the tangs on the cap or the gasket itself will not provide a good seal. Yours maybe releasing pressure, ever so slightly.

DUB

Unless I am wrong...adn I doubt I am. I will comment on what I have experienced working on these cars.

IF the thermostat has no hole drilled in it to get the air top pass by it when filling the system. And a person fills up the system. And if they remove th heater hose onteh intake that goes to the heater core so AIR can escape when filling up the radiator. And they keep filling the system until coolnt starts to coemo out of the fitting wher the ehater hose is attached. Then they put the heater hose on and pressure test eh syste, and ALL IS GOOD.

Whenteh engine is ran and allowed toget hot adn PRESSURE is onteh system. Any aior that qwas still ithe system due to the complexicity of the cylinder heads that can hold air has now gotten toteh top of the radiator. When this air gets relaeaseda nd intot eh over flow reservoir that ash cooanlt in it.

When the engine begins to cool down,.,,it will draw coolant back INTO the radiator for the next time it is run.

I have filled up the over flow reservoir on many cars and when I get the engine to operating temp and the next day when I came back in and looked at the level of the reser4voir....it was DOWN a lot.

I know this to be true due to working on a many C4's that have a 'low coolant' light. And when I do these cars...I have run into when the thermostat opens...the 'low coolant' light will shine....even though I had filled it up all I could. And the engine is NOT overheating, But the next day when I come in and see the over flow reservoir is down a lot. And I run the engine again. And the thermostat opens and ...the 'low coolant light does not come on.

I myself would check the coolant system like I had mentioned and NOT assume that the new radiator cap is good. I check it also. And I also verify that the hose form the over flow reservoir is a good hose and not leaking.

DUB

dmaxx3500

,open the over-flow tank,fill it 1/2 way up,start car,turn on heater/hot,let car idle,leave cap off,run it for 10-20 mins,turn car off,wait 4-5hrs,and do this again,it should burp/purge any air out

DUB

Leave the cap off of what? No need to leave the cap off of the over flow tank...it is not sealed. Because I know you were not talking about leaving the radiator cap off while it is running.

The system needs to be verified that is holding pressure for it to 'burp' out anything....ergo....pressure testing it to make sure it is sealed.

DUB

OldCarBum

LenWoodruff

I checked the radiator and it was full. I added coolant to the reservoir to the recommended cool mark. I let that sit overnight and there was no leaks for the reservoir or line to it.

I drove it today for about 30 minutes to warm it up with the AC on. Then turned the AC off and the heater on full heat for the last 10 minutes of the drive.

I have been back about 30 minutes with the car off in the garage and I hear a few gurgles but not as much as yesterday.

And no leaks yet.

doorgunner

Along with the advice other members have given drive with the heater on for another 10 minutes of circulation the next time you drive. I think the blower should be set on "Low" so you don't have to "sweat out" the 10 minutes with it turned on. It took a while but I gradually stopped the system from dumping coolant, then got it to down to gurgling with only minor overflow into a temporary "catch-jug", and finally to minor gurgling without a catch-jug. (My 1968 car has the aluminum expansion tank which I connected the temporary catch-jug to the overflow tube)

There is the RARE chance that one of the headgaskets is not correctly "ported", meaning the coolant is not flowing properly through the head because the head gasket has one of the coolant passages blocked off. Comparing the new gaskets to the old ones before installation eliminates that problem. I have seen that problem only once and would not be concerned.

HeadsU.P.

You can't burp out air if the Rad Cap is still in place. Where are the bubbles / air pockets going to escape?

After a coolant flush / refill I purposely leave the coolant level well below the filler neck, about three inches. With engine idling you can see the air pockets purge out of the rad. After 20 mins or so, you top it off and seal with the cap. All this is done with the vehicle up on ramps.

DUB

SO you guys are telling me you run an engine for 20 minutes with no radiator cap on it???

I know about 'burping' the air out...and have done it on engines where there is no hole in the thermostat. But leaving the cap off for 20 minutes is something I choose not to do myself due to one I see the thermostat has opened....I perform a different procedure at that point.

I DO AGREE that the coolant needs to be about 3 inches down form the top of the radiator....or you will have coolant gushing out when the air burps.

DUB

HeadsU.P.

There are two kinds of people in the automotive world.
One fills the system, slaps the Rad Cap on and hopes for the best.
The other one fills the system, leaves the Rad Cap off and closely monitors, and I mean closely, what's going on in the rad. Watching every minute for anything unusual floating by the filler neck. Watching for any signs of oil, trans fluid, metal, and the flow of coolant, etc. Waiting patiently for the big burp event to happen and the coolant level takes a dive. Add coolant, monitor some more.