Weird Cooling Issue- Overheat, no heat?

[jeffmn8]

Alright, so here's the deal. A little background first, my 91 318is has had an s50 in it since July, with an m42 radiator and expansion tank. The motor was refreshed with a new headgasket before it was put it. It has been running perfectly since the motor was put in.

So yesterday, I was driving down the interestate, and had the heat going cause it was pretty chilly out. After maybe 10 miles, the heat stops blowing warm. I think, hmm that's odd, so I mess with the controls for a second then pull over (And no my coolant temp sensor doesn't currently work :(). A little steam was coming out of the cap. I turned the engine off and let it cool for a bit. I popped the cap off and it sprayed a bit of coolant along with this brown foam-like material (see picture below).



Got the car towed back to work to take a look. My first thought was that the water pump disintegrated since it lost heat all of a sudden. Pulled the thermostat and water pump, and they both looked fine.

So now I'm sitting here kind of stumped... Is there any way that the heater core could be the culprit? I haven't noticed any dampness in the cabin. Any insight is welcome!

[scottinAZ]

looks like some packing material made its way into the system. Flush the system, and see if any more crap comes out, refill, bleed and see what happens. chances are that some of that crap is plugging a passage, and most likely the heater core.

[jeffmn8]

Yeah, I'm going to flush it out here shortly. The question is wtf is it and where did it come from???

[cabin]

No idea what it is, but it looks just like the foam liner stuff that is on the hood.

[jeffmn8]

No idea what it is, but it looks just like the foam liner stuff that is on the hood.

I believe you're right! After the cap blew, i guess it took some of the lining off too. Now, the question is why did it overheat..

[jeffmn8]

I tested the thermostat while it was out and it worked fine. The m42 radiator is a pain in the ass to bleed... I backed the car up on the loading dock at work to bleed for a bit. Drove it back home and the expansion tank was half empty. Luckly it's only a three mile drive from work to home, so I'm just going to check it/bleed it every time I go to/from work.

I'm still curious as to what cause the issue in the first place...

[328ijunkie]

M42 Rad. Yuck. ;)

It may not have been bled all the way.

[325islovE]

exact same thing happended to me, minus the black crap... all i could come up with was air got in there some how. I noticed that when i pulled over the top radiator hose was hot and the bottom hose and radiator where stone cold.

[jeffmn8]

Little update from today... I got my Autometer water temp gauge installed into the head after work, then took a quick drive 60 mile drive. On the way there, it was running a little hot, around 210F, heat was in and out, idling kinda funny at stops...

I made a stop and topped off the expansion tank (which was halfway empty) The car wouldn't start... just crank and crank and crank. I plugged the other temp sensor connector onto the stock sensor and it started up fine... Whoops.

So on the way back it was at a solid 180F the whole way with the heat good and hot consistently. So I guess it just sucked in a bubble from somewhere?

Now I just need to get my gauge retrofitted into the cluster...