Percolating Radiator

[placelast]

This week there's this strange reoccuring situation when my I park my '95, 3.4l auto; it has this sound coming from the radiator & engine like the old-fashion coffee pots. Sometimes it peaks and spits fluid out of the overflow.

It may have caused the original radiator to blow, so I replaced it with an fully-metallic one along with a new thermostat, but this condition still occurs.

The temperature gage reads normal.

Anyone have an idea what might be the problem? Thanks.

[wylcat]

sounds like you have one of 3 possible problems, first of which can be a simple fix. its possible that your coolant is too diluted, ie. water boils at 212 deg, adding antifreeze raises the boiling point. the second could be trapped air in the cooling jacket, there should be a bleed off at the top of the engine on or near the upper radiator hose. the third is the INFAMOUS head gasket problem on the older v6 engines. if when your radiator went the first time, and you over heated the engine AT ALL, you most likely have a compression leak into the cooling system. If you have access to a compression tester you can use the threaded end with compressed air in each cylender to confirm a blown gasket or cracked head. if you see air bubbles in the radiator its done.

hope this helps you figure it out

[KLS]

Only pure water at sea level pressure boils at 212°F. Pure water under the .9 bar (13 psi) pressure of my radiator cap boils at 245°F. 50/50 antifreeze and water boils at 223°F at atmospheric pressure and about 265°F with the pressure cap.

Agreed, it sounds like air in the system or a head gasket leak.


Ken

[placelast]

Thanks, guys - good info.

More information would be in order: It has shy of 260k miles, so I've certainly gotten my money's worth. Almost all has been easy non-stop freeway, being a slow-poke driver in a remote part along the coast of CA. The original head gaskets were replaced by the maker at 100k before any symptoms. Perhaps it is ready for replacements, unless those were just that.

I am using a 50/50 mix, and have been told water carrys heat better or is more efficient than antifreeze, although I have added both to keep it at that level.

My wife said her father and three other old-time auto mechanics said higher mileage vehicles fair better with a bump up in the cap pressure. It has a .9 and I bought a 1.1 to try once it cools down unless that seems foolish. It is a cure for big-bore four stroke dirtbikes designed for higher speed conditions when ridden at walking pace.

As far as "burping" the system like a motorcycle, the Toy dealer did my timing belt and water pump yesterday (pump was making noise, and with the spitting/percolating I figured the pump was not doing it's job); one would think they would have burped the system although there is no guarantee. I'll look for a device to do so.

Having them pump in compressed air sounds like a way to go if all else fails.

[dsrtrcr01]

To burp it just start it when cold with the cap off and turn the defrost on high and as hot as possible and let it run for a while. This usually does the trick But i have run into some stubborn ones as well. If it is a 3.4 it does not have that infamous headgasket problem, only on the 3.0 V6.

[placelast]

Ran fine today; no spitting nor percolating after a stop. It's still a possible, and as such may not take any camping trips far away from civilzation any more.

The 3.4l - at least mine - was called in for the headgasket.

Thanks for the idea on how to burp the baby.

[dsrtrcr01]

They initially had a problem but nothing like the 3.0V6. Once you have it replaced you are good for a while unlike the 3.0 where it could go out a few hundred miles later. I am sure when they did your water pump they took care of any air problems if you had any because they would have had to replace the coolant and burp it in the process.