why won't my car cool?

sleeper

sleeper

Former LOD President
So I finally got the new motor in my '93. Junkyard motor, supposedly has 98k miles on it.

Took it for a drive, everything is good except for an exhaust leak, but the temperature keeps rising. I get home, and there's a hole in the radiator, and steam / coolant are coming out. I replace the radiator, fill it up, and run it. No more leaking, but it's still getting hot.

The car isn't really overheating, it's staying in the "normal" range, but it gets up to the N or O and stays there. I haven't seen it go past the N, and i've let it run for a while, but it is getting hotter than it should. IR gun on the crossover tube is showing up to 225°F. A little hotter than it should be.

Thermostat is from the old motor, and was new in the fall. It was working fine before the old motor blew up. Radiator is new.

I burped the air out of it better today but it's still doing it. I can't let it run for too long with the funnel jammed in the crossover tube because the coolant / water start boiling and that kind of defeats the purpose of burping the air out of it.

So, any other ideas? Water pump maybe? Head gasket maybe? no water in oil, so i'm hoping it's not a head gasket. Motor has a warranty but it was a pain in the ass to install and I really don't want to take it back out.
 
Of all of the posts I remember (remember being the operative word) reading about burping the cooling system, I just dont remember reading that you burp it with the engine runnning. I recently replaced a waterpump on my 95, and I'm sure it wasnt running when I burped it, and it seems to run in the mid normal range.
 
I had to run mine on the road until up to temp, let it cool and refill a number of times......Can't cheat either.....only fill until you see it come up to the full line on the bottle.
 
The fan is coming on. I can't verify whether it's running as it should or not, but when the temp gets above mid way it comes on, when it gets hotter it goes faster. But in test driving it (up to 35-40 mph) it doesn't seem to cool any better.

Condenser is no dirtier (cleaner, maybe) than when the car was running previously with no overheating issues.

I have not tried a new cap on the resevoir. Do you really think that could cause the problem? I did notice a small amount of coolant seeping out of the resevoir under the cap when I first started burping it yesterday. When I removed and retightened the cap it stopped but didn't improve the situation. When it's all closed up and getting hot, it doesn't leak.

I found a post saying burp it with the engine running, and let it run like that for half an hour. In my previous experience on several different vehicles, when you fill it the procedure is to start it with the fill point open, run it until the thermostat opens up (you can visually see the coolant drop at this point), top it up, close it up and you're good to go. That's also how it has always worked on the mark 8 (other marks at least) for me, but having the motor out and having all of the coolant out of the engine, new radiator, etc. I thought it might take longer to get all the bubbles out. I've never had this much trouble with it.

Could this be a symptom of a bad water pump? I'm not seeing any seeping from the pump, and I'm not seeing any coolant behind the pump under the intake (although it's pretty hard to see back there). I've never known a bad water pump to stop pumping water, I thought they pretty much all just started leaking (and in theory eventually lock up).

Maybe i'll try a new cap today, and try topping it up a couple more times.
 
For as hard as it is to put one on I would do it due to age (blade erosion). The bearings would cause the seeping problem.
 
The first thing you need to understand is that you are burping it to get air out of the highest point in the system, and in this case it is at the top of the heads and coolant crossover tube. Running it up to driving temp allows the thermostat to open and circulate air and coolant in the system to flow to the highest point and naturally rise to the top. That is why you fill it at the crossover tube, without the engine running. This is also why it may take several tries to get all of the air out. You should also have your heater turned on high enough too circulate coolant through it.
 
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I picked up a new cap on the way home, I'm going to try to burp it a couple more times tonight. Hopefully that does the trick.

Car is due for paint, so I'll be breaking out the flat black quickcolor again tonight too :)
 
I have had more than one vehicle cooling system 'fixed' with a new coolant bottle cap. The first thing a cap does is raise the system pressure to effectively raise the boiling point of the coolant. If the coolant even starts to boil the cooling capacity is greatly diminished.
 
I changed the cap and burped it with the engine not running. Still heating up. Got up to the O, it's cooling down now.

I pulled the water pump off my old motor. One of the vanes has a big bend in it and it still cooled just fine. I have a hard time believing the pump on this motor isn't pumping, based on that.

I could change the thermostat but the radiator is getting hot, so that should mean that it's working, right?

I'll try burping it again and see if that helps.Getting kind of discouraged here. Motor seems to run fine except it won't stay cool. I just want to drive the damn car.
 
burped it again. Same thing.

I started it, it got to the R, the fan came on, it dropped, fan went off, it rose again and didn't stop when the fan came back on.

It's getting another new thermostat tomorrow. Hell, maybe i'll put a water pump on it while i'm at it. The coolant for the damn thing is almost as much as the water pump costs. Local advance has thermostat, water pump, and both gaskets / orings in stock. Should be under $100 with coolant. If that doesn't fix it, I just don't know WTF else to do.
 
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....but it's NOT really overheating at all is it? Is it puking coolant?

If you suspect a leaking head gasket, you can buy test strips that will check for exhaust contents in the coolant. Much better than tearing down the engine.
 
If it's a bad head gasket, a can full of gas and a handful of matches may very well come into play.
 
Advance didn't have the test strips. I bought a thermostat, water pump, and gaskets for both. Pulled both out of the car.

Water pump looks good, no apparent wear on any of the blades, nothing bent, no apparent corrosion, it turns freely with a little bit of resistance, like the new one, not totally freely like the one on the old motor (the one with the bent vane) though.

I'm debating whether to install the new water pump. I think I might just save the $45 and put the old one back on.

I boiled the old thermostat. It says "195" on it which I think is too high. It just barely starts to crack at 195 and itsn't fully open until the water is at a rolling boil (used a meat thermometer in the water). First time I tried it (I repeated it like 3-4 times) it didn't open in any way that I could notice until after it was boiling. I think the thermostat is faulty, I will put the new one in.
 
New thermostat seems to have done it.

Old water pump is back in with a new seal and it's doing fine.

Car is running on the M now. When I stop, it rises to the top of the M, the fan comes back on, and it drops back down to the bottom of the M.

New thermostat is a 188. Advance's website says it's a 188, but they're computer at the store says it's a 195. It says 188 on it, though. Old one said 195 on it.

Woohoo! I now have a fully functioning beater. Except for an exhaust leak or two and a discharged A/C system. But that doesn't stop it from being driven. Now I can save a few bucks on gas.
 
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