Did I Blow Head Gasket?

[mattyd7]

With the mild winter we've had in New England, I've been running my spider weekly to keep everything fresh and lubed. My typical procedure was to start it up and let it high idle until the fan comes on while I poke around and inspect everything under the hood to make sure it looks and sounds right. Once the fan comes on, I'd turn it off unless the weather was really good and I could take it for a quick ride.

Friday I was doing this, pretty pumped because its supposed to be 70 out this week. I realized it seemed to be taking a while for fan to come on, and then notice funny smell and freak out. Engine temp was much higher than usual fan activation temp, so I shut it off. Had some white smoke coming from radiator. Temp gauge when I shut it off was probably a full needle width past 190, so not super high but higher than its ever seen since I've owned it.

Did some diagnosis and figured out it was the fan switch. Fan works if I jumper it. So thought that was all I needed to do and I'd be good to go, so ordered a new one.

Next day, I was thinking I didn't check to make sure thermostat opened, maybe the bottom of radiator was not hot enough to activate switch so I should double check and rediagnose to be sure. Planned to warm it up close to 190 then check lower radiator hose, and then jumper fan so it would act like normal and not overheat. Started car up, no problem. As it is warming up, my radiator cap is spitting coolant. Shut it down. Once it cooled I removed cap and cleaned it off and inspected it. Looks good, rubber is supple not stiff or cracked. Cleaned cap opening. Replaced cap.

Tried again, same thing. Pretty much when the needle starts to move past 90F on the temp gauge, I get a steady drip of coolant out of the top of the radiator cap. Not from under cap, it is definitely coming out the top relief valve opening.

I am worried that the overheating caused the head gasket to blow and that is causing the high pressure overflow at cap. I believe it makes sense, even though the engine didn't get THAT hot, who knows how old the gasket is so maybe it was enough to kill it? I have been running through other possibilities, but what else would cause a pressure spike in coolant system like that? Especially knowing there was just a overheating incident.

I am going to try replacing the cap tonight to make sure its not a failure of the cap, but that would seem highly coincidental to have a radiator cap failure exactly after the overheating, right? Plus the cap is a pretty simple device.

Thoughts? Other ways I can confirm the diagnosis of head gasket failure? I read to try running engine with radiator cap off and rev it up to see if it overflows, may try that next. I don't have any milky residue that I can see at cap opening but the car has not been allowed to run much since the incident, maybe 5-10 minutes at most so I'm not sure how much contamination would have gotten in at this point.

Thanks for the help.

[124JOE]

did you pull the dipstick to see any milky oil?
if not oily then you are probably ok

[TX82FIAT]

You said white smoke from radiator. Did you have any white smoke out tail pipe? did your overflow/expansion tank fill up and is the coolant in that tank clean. It could be the radiator cap failed or there is a clog not allowing the pressure to release into the overflow tank such as a kinked line.

[mattyd7]

The expansion tank did it's usual thing as far as I remember: as it warmed up the level went up a bit but nothing out of the ordinary. I know I watched for that because my first thought was maybe the hose to expansion tank was clogged causing pressure spike. I will keep an eye tonight when I check again but I think that is OK.

There was no white smoke at tailpipe yet. I would notice because I have it in my garage and it would be pretty obvious in an enclosed space, that's how I saw the steam at the radiator so quickly and shut it down. I do have door open to vent exhaust gas of course though.

As far as cleanliness of the coolant in the expansion tank, I will check that tonight also. The possibility of head gasket failure hadn't really hit me until I was on the commute to work this morning, so I wasn't paying particular notice for contamination. I only know that there wasn't any milky buildup on the radiator cap because I would've noticed that for sure as unusual when I removed and checked the rad cap. But I'll look for oil film/sheen in expansion tank, good idea.

Joe, I will also pull dipstick and look for residue in the oil too.

[KevAndAndi]

If that temperature did blow the head gasket, you're lucky it happened at home. And that's really not a high temp, so the gasket must have been pretty bad.

Hope it's something simpler, though.

[mattyd7]

Just as a follow up, after thinking about things more and looking at everything with the intention of proving a head gasket failure, I've stepped back from the ledge and think everything is probably OK.

Checked again and exhaust seemed normal. Ran engine with radiator cap off and didn't get any bubbles. Coolant looked clean, no oil. Dipstick looked good, no water in the oil. So with all of this, it would be hard to believe that I blew a head gasket to the point where enough exhaust gas is getting into coolant system to blow rad cap relief, but not present any oil in the coolant or bubbles at the radiator, etc.

Last night I finally had all the parts I ordered in and replaced most of cooling system. Fan switch, thermostat, radiator hoses, radiator cap. Filled with fresh coolant. Ran it to hot, fan came on, everything normal. No coolant coming out of the new cap.

I'm now wondering if the old radiator cap was nearing end of life, and when the car overheated and that caused it to pop, something inside was then busted and it was popping at less pressure than it should. It was the cap that the car had when I got it, which was not a correct Fiat cap, it was one of the ones with the safety lever on it. Now it has the correct one from Autoricambi.

It was raining hard last night and this morning so I haven't actually been able to drive it to call the matter closed, but running it in the garage everything seems much better! The fact that it isn't spewing coolant as the engine hits 100F is a great improvement

Thanks for the help guys.