Just an update, water pump was trash. Water was leaking thru weep whole. replaced with electric and now all is well.still running about 220 but doesn't climb past that. Contributing to Texas heat on that one.

 

throw a bottle of water wetter or royal purple's ICE in there. It should help a little.

 

good idea, that might get me back down to normal 210 but like I said still WAY better now

 

Hey all, long time reader, first time posting here.. =)

I just had my 94 Z28 overheat on me finally last night on the way home. I've been watching the gauge for the last few weeks, it's been getting up there almost to the 3rd tick on the gauge, usually it cycles between the first mark and the middle half way mark on the gauge as the thermostat does it's thing.

However over the last few weeks I've been noticing it getting up there and then dropping back down to the middle mark or so. But last night I'm cruising down the freeway at a nice 85 or so and the needle went above the 3rd tick and I wasn't really in the throttle too hard at that point, so I pulled over and sure enough it wasn't going back down, and had boiled off a good amount of coolant already.

I was able to nurse it home keeping the temps down and re-filling with water as I went. It just boils off the water REAL fast, with the motor hot already and filling it with water I get maybe 10-15 minutes drive time before I need to shut it off again and repeat. And when I leave the cap off, warm it up until the stat opens it will force coolant out.

What do you guys think, clogged radiator/line? I tore into the pump, checked the fairly new 180F stat and it looked ok, good seal still on it. The pump is like 2-3 years old at least and the impeller had some marks on the blades like debris had got in there but nothing that looked bad at all. No visible leaks! The underside of the car is dry until it overheats and the overflow um overflows a little..

Also I've checked for a head gasket, I literally just changed the oil 3 days ago and it's clean as can be, nothing but oil in there. As for the coolant, I flushed most of the stuff in there out and the only thing I saw was a little rust come out but no oil. And there's no visible smoke out of the exhaust..

I have a stock ECU and thermostat swapped in right now, so ignore what I have in my signature please, thanks.

What do you guys think? I'm a little lost here..

 

So it looks like it was a combination of things causing my issues.

My radiator cap was worn out and not sealing to 17lbs. so I replaced that and found the weep hole to have a very small drip coming out of it, so I replaced the water pump. And then the real fun began when I discovered both sides of the plastic (OEM style) radiator were cracked and puking coolant all over the place.. =(

So a new radiator, cap, pump, and all is well.. I'm still kinda surprised no leaks were visible initially tho.