Two years ago I had this problem, would blow coolant out of cap on resevoir. I had been hearing a gurgling noise for a while under dash. Mechanic said I had a blown head gasket. Motor had 267,000, so rather than rebuild top end I put in a used motor with 90,000. Shortly ther after I had to put in a new heater core. The gurgling noise was back and has never gone away. I have only put 12,000 on this motor since install. Came home last night from sons hockey game with coolant blown all over underside of hood by res. tank(heard a hissing/leaking noise). Do I have another blown gasket or cracked cylinder head? Is there any other reason the cooling system would be taking on pressure?

 

How is your coolant mixed? If you have too much water in it, it will begin to boil over.

 

If it's blowing out and there is high pressure in the reservoir, then yes, you likely have a blown head gasket. I know it's hard to believe but it's a chance you take when putting in a used motor unfortunately.

 

Stuck thermostat, defective Water Pump, clogged radiator, Combustion gases coolant.

When you swapped the engine did you do a coolant flush and install a new thermostat? Did you pull the water pump to check its condition? There are kits available to test for combustion gasses in the coolant. Most competant rad shops will also do this test.

 

Funny, I didn't see anyone mention a faulty radiator cap. Seems like everyone wants to go for "blown gaskets" before checking the basics. If the cap doesn't hold the correct pressure, then it will blow coolant out of the top of the reservoir...under the radiator cap. Also, the gurgling noise is due to air in the cooling system. The system needs to "burp" after filling with coolant to get rid of any air pockets trapped inside. Pressure test the system and make sure that you don't have any leaks, too. Could be just getting air in due to the coolant coming out of the reservoir. Keep us posted.

 

Blowing out coolant would mean its over heating usually. I would replace the thermostat and fill coolant/water in a 70-80/30-20 mix or so being you are in MN and you dont want the coolant to freeze. 50/50 for summer mix. Also when you fill up the coolant, you have to fill the radiator up and wait for the Thermostat to open. When it opens the level in the radiator will drop quite a bit and then you fill full. Once its full put on the radiator cap and fill up your reservoir bottle.

A bad radiator cap will not hold the standard 16PSI the cooling system creates thus spilling onto the ground.

 

I would have it tested for exhaust gasses if it has them you have a bad gasket or a crack.
If it doesn't then I would figure out whats wrong with the cooling system. Sounds like a gasket or a crack to me. First step is to have it confirmed with the co2 test.

 

I hope to get to shop this week(truck is parked) and check for CO's in coolant(fingers crossed). Will go from there. Yes, when we put in the used motor we;flushed coolant-replaced water pump & themostat. Interesting side note on the thermostat. My temp gage was climbing into the high range rite after motor replacement, but only when I was pulling a load. To get it to drop back down I had to stomp the throttle to the floor(high RPM's) and it would instantly drop! Turns out the thermostat(aftermarket from NAPA) was different from the OEM motorcraft thermo. Put in the motorcraft thermo. and the problem went away. The gage has yet to move out of it's normal operating position since, even when pulling in high heat conditions. Thanks for your suggestions, will post my findings when I get them.

 

Correct me if I am wrong, but wouldn't a head gasket failure cause coolant to burn... which in turn would cause white smoke through the exhaust? I guess if it was minor enough you wouldn't see it...

Regardless, I have the same issue... but I just filled up my coolant system when I bought the truck... and I think there is just air in the system.

Regards,
Jeff

 

Disconnect the heater core lines and blow the hose thru them. Then refill, let the system burp. Recheck. 10 to 1 there is a clogging or there is a massive bubble in the system. Do you frequently use the heat? If you don't cycle the heater every once in a while. Coolant can conjell and gunk up in the heater core lines.

 

Agreed,the return has that brass reducer inside the rubber hose, - might be a good idea to flush her both ways a few times as well.

 

Always happens to tauras and sables. Deal with it every winter time. Flush heater cores daily. 2-5 a week lol

 

The coolant systems with the modular is pretty sensitive to refilling. Ideally you want the coolant reservoir to be the highest component in the system. That way any air will travel to the high spot( bottle) and burp. With the design of the modular system engine coolant outlet being at the very top of the engine it becomes the high spot. So any air that's in the system tends to stay there unless a little time is spent refilling while the engine is running. At the assembly plants they fill under pressure so that eliminates the problem usually (not always). The body design actually dictates where ( how high) the coolant reservoir can be placed. The Mustang 4v's are even more sensitiive. You are going to build a small amount of pressure in the coolant system (normal) while running and you want that. Good suggestions here on what to look for though. You may want to check for a crack in the bottle, a kinked heater hose as well. Someone mentioned smoke out the tail pipe which is right but sometimes it's so little that its hard to detect. I would have the Hydro Carbon test performed as others suggested as well. Just my 2 cents. Good luck.

 

Your Head Gaskets are leaking. If you are lucky you can remediate the problem with a solution of Barrs "Head Gasket Repair" Solution. That is Head Gasket not radiator stop leak.

 

I can smell antifreeze burning on the engine block after I drive it, which isn't often obviously, cuz I still haven't repaired this problem(have been out of work all year). Is that a head gasket leak, or a leak from some other gasket or thing? I've put a different cap on the radiator and haven't had it blow coolant since the original time, that doesn't mean that's what it was though. It's still gurgles when driving and smells like burnt coolant(outside the truck) after driving it. Again, this is a used motor with 90,000 I'm not a huge fan of "fix it from a bottle" stuff. I don't like the idea of pouring **** into the systems of my vehicles motor. Maybe I'm just paranoid, but I'd rather find the problem and fix it, rather than put a band-aid on it. Again maybe I'm way off base here, open to anyone's opinion on this. One of these evenings I'm gonna get over to my mechanic buddy's shop with a case of beer and crawl around under the hood and find where the coolant is leaking onto the block. Thanks for all the suggestions thus far. DC