Hot Engine: Leaking Coolant

First incident: Engine light came on. Pulled over immediately. Coolant leaked out.Cooled car down, added H2O and drove to nearby dealer. Ford dealer- diagnosed- needed new radiator, needed one new heater core hose. Approx. $800. to fix. Took to my local mechanic. Put new radiator ($160), two new heater core hoses ($200.), new radiator hose($15), coolant$25…$200.labor. About 1 mos. passes- Second indicent- Engine light comes on…pull over immediately… call mechanic- diagnosis- loose clamps from previous work. No chg. About 2 months pass-Third Incident- Engine light comes on - fluid leaks out- pull over-call mechanic-towed- same drill- mechanic replaces an O-Ring on a gasket that sits on top near the radiator. $80. 2 weeks pass- Fourth incident- Engine light comes on- pull over on major freeway- coolant leaked out- mechanic comes to me-towed- He says the clamps are loose again. No chg. Wants me to drive over the weekend and come back to check.
Could this have anything to do with the Heater Core? Something is causing this pressure to build. I’m a female with no mechanical background, just sixth senses and a lot of patience with this nice mechanic that doesn’t seem to really know the cause!

With Each Overheating Incident Comes The Increasing Risk Of Engine Damage That Can Lead To More Overheating, A Vicious Cycle.

Very few modern cars can stand overheating without damage. Although the mechanic (“that doesn’t seem to really know the cause!”) may be very nice, you need to have this properly diagnosed ASAP, even if by somebody else. A cooling pressure test should be performed to help find the source of the leak(s).


This is difficult for us to diagnose since you have apparently not looked under the hood yourself (or had the mechanic show you) to see the actual source of the leak. Loose clamp? Really?! Even a novice can tighten a clamp properly. Something else is afoot.

You did the right thing to stop driving immediately so as not to risk engine damage. Engine should be OK.

For now, closely monitor the level of the coolant in the plastic reservoir, perhaps every day. If it holds steady, relax. But if it steadily drops you have a problem. In that case follow CSA’s answer (above) and find a real mechanic who will perform the pressure check.

Can you at least say something about where the coolant is leaking from? When the engine light comes on are you saying there is a warning light for overheating that is coming on? Is the overheating happening because you are losing coolant?

In all of this has the thermostat been changed? The radiator cap? (The radiator cap is a pressure release by design - if its sticks closed that can cause pressure problems).

Has anyone checked for signs of a bad head gasket?

I think you need a new mechanic.

Thank you for your responses- I forgot to mention that the thermostat was replaced after the 3rd incident. I noted that the temp needle on a couple of occasions would spike up and then immediately go back down, thus I the thought that maybe it was the thermostat. I suggested this to the mechanic and he replaced it for me. ($129. parts/labor)
The mechanic did not confirm an exact location of the leak. I also looked under the hood and could not determine an exact location. At that time EVERYTHING was wet. I guess I assumed that since it was a clamp issue, it was leaking from one of the hoses. If you have any recommendations of mechanics in Irving, TX or surrounding area, let me know.

First, of all the modern engines, this one is less likely to have warped or cracked heads as a result of overheating. The heads are heat treated and aged before machining. I would suggest that you replace the radiator cap. It is so often overlooked when it is the problem to begin with. And its cheap.

I’d also do a new radiator cap before anything else. Pick one up for about $7-8 the next time you’re out. Then after the car has sat overnight - or similar (it has to be completely cool) - just remove the old & install the new.

There is supposed to be “pressure” in the cooling system of a hot motor. The question is are you getting normal pressure or excessive pressure? Have they tested the pressure at operating temp? Excess pressure means a new radiator cap and is not expensive in most cases.

At this point I’d have lost faith in the shop that put in the radiator and is trying to figure this out. Perhaps they went “cheap” on the original job and reused the original hose clamps. This isn’t a good practice and leaking is a common problem when you reuse old clamps. On the second trip back to the shop they should have replaced any and all used clamps with new ones.

Look at the hose clamps on the radiator than you can see, they should be shiney and new looking. If not, tell the shop to replace ALL the clamps on all the hoses with new ones. This could all be a case of “weakest link”, where one clamp leaked and when it got tightened up another clamp leaked elsewhere in the system, and they tighten that and then … and so forth.

Another reason for leaks that won’t go away is a shop uses the wrong hose(s). Hoses are now often shaped and have to be the correct diameter to fit properly. A too large hose diameter will make it hard for a clamp to hold under pressure. “Universal” radiator hoses are “flexible” hose (they aren’t smooth, but have “rings” that allow the bending) and some of these hoses don’t work well in certain cars.

It might be best to take the car to another shop if this leaking problem persists.

Thank you again for your comments. Yesterday, on the way to a wedding reception, the car overheated once again. I quickly pulled over, raised the hood and noted the coolant leaking from around the base of the cap on the coolant resevoir.
I left it in the parking lot of a church, called a friend for a ride home. Will be dealing with it this morning. I noticed about half of the liquid drained out while the engine was cooling down and pressure, I’m assuming, equalized. Should I simply go buy a new cap and then fill the coolant back to the top ? I called the mechanic yesterday when it happened. He was out of town and could not assist. I mentioned all of your suggestions. He stated that he had thought about the cap. He also mentioned “bleeding the system”… as if this needs to be done now… What does that mean? I was hoping I could change the cap myself and add the coolant and drive it home…

A cap is easy. You wait till the engine is cool. You push it down and turn it counter clockwise. You will have to push pretty hard. To put on the new one push down and turn clockwise. Add fluid and let it run with the cap off until it warms up and all the air comes out. You have to let it warm up so the thermostat opens and then it will need to be topped off with fluid. 50/50 mix of antifreeze. You can buy it premixed.