Overheating after new radiator

[Mendo]

A little background on this situation.
My radiator fan blew up for the 2nd time and took out my radiator. I had a new radiator installed and drove it for the past 5 days without the fan while I wait for it to come in the mail. It drove fine and never overheated even in extreme situations (hawaii heat stopped in traffic)

The other day I noticed a leak from where the top hose runs into the expansion tank, I tightened up the clamp but it would still leak semi slowly. As I was driving home uphill I noticed the temp guage start to very slightly but steadily get hotter so I immediately turned it off and pulled over. I popped the hood and coolant was pouring out of the expansion tank cap. I let it cool down for a bit and added coolant but it was pitch dark so I could not really see how much I was adding. I started to drive again at a steady pace on flat ground and the temp just kept rising again so I pulled over and had it towed.

Is the leak from the expansion tank causing this overheat issue, or is it something else? Thanks for any help its been one thing after another with this car lately, I miss driving it already!

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[UnderCoverGuy11]

Turn on the heat, did it stop working? Sounds like a bad bleeding issue to me.

[xlDooM]

The tank cap is supposed to leak above 200kPa (it's written on the cap). It can leak when you overfill the tank, or when the coolant gets way too hot.

I would refill when cold, look up flyfishvt's bleeding video (that sounds wrong lol), try that before you throw money at it. It's strange that the car ran fine for 5 days and then overheated, but it's possible the leak drained so much coolant out of the system that it overheated and boiled what was left. Either way you need to fix the slow leak in the expansion tank. The plastic neck (if it is a part plastic tank) could simply have a crack in it (common problem).

[Richkid79]

Could be a couple different things...you probably shouldve replaced the thermostat at the same time you changed the radiator. If the thermostat has a problem, it could cause too much pressure to build and cause make it leak out. Also it could be as simple as too much air in the system, thats what the bleeder vlaves in the hard lines are for. This has happened to my E39 before. What I do is take off the small plastic screw in the hard like and start the car. With the engine running, add water through the little hole while squeezing both the soft upper and lower radiator hoses to get the air pockets out. If you look into the hole (be careful, you can get burned) you will see water flowing through the line. The idea is to get as much water into the radiator and engine block as possible, which forces the air out. If its done properly, this may cure it. If not, I would look into a new waterpump. The worst thing that can happen is you blew a head gasket, or even worse warped a head. The easiest was to see if you warped a head it to look at the engine oil for signs of oil and water mixing. If it has water droplets on the underside of the oil cap, or if the oil looks a bit like chocolate milk, you might have done some damage to the top end of the motor. The fact that you ran it for 5 days leads me to believe you simply have air pockets in your system. And do fix the expansion tank leak, losing water means gaining air and air heats up way faster than water. Hope this helps

[Mendo]

Thanks for the tips guys. I do not think I did any damage to the engine. I turned it off way before it got anywhere near the red.

It could of been something as stupid as loosing so much coolant through that leak that there was so little coolant left it boiled off what was left. I am going to look into bleeding it. I have also ordered a new expansion tank and cap so hopefully that takes care of the leak.