In regards to a 93 SC400. Car was overheating, pop the hood, leaking from the sensor on the overflow tank.

Replaced sensor > drained radiator > Very little room to add more coolant to overflow tank, but i do what i can > Car spits out coolant/air like crazy during idle.

Parts that have been replaced in the past 60,000 miles: thermostat and water pump.

If i let the car idle with the cap off, it spits out coolant but temp is fine. If i put the cap on, temp goes up and leaks from sensor.

Please just tell me there is air in the system. I've been trying for an hour to get the air out. Any tips?

 

try replacing your rad cap. and bleed out the air..

 

i just blead it through the radiator cap right? just leave it off and let it bubble out? that's the only way i've ever known to blead a coolant system.

 

You probably need a new gasket for that sensor. Try turning your heater on full blast with the cap off and add coolant as needed. It shouldn't be boiling over. Let us know how it goes.

 

the sensor came with a new gasket. i noticed a hairline crack on the tank that originates from the sensor hole. i put 2 layers of silicone on the crack last night. i came out this morning and i was able to put a lot more coolant in and the car 'burped' up air but not nearly as violently as before.

with the heater on max, i got more burping, but no heat inside. i checked the heater control vavle and it is up when it is on max heat and down when on max cold.

is it possible it is the water pump? if it's not functioning the water at the bottom is getting so hot and boiling up to the top? or maybe it's just a lot of air in the system? i am letting it cool down now and i will try to bleed it some more later.

 

the crack on the coolant tank is common, since its under pressure its doubtful silicone will hold.
theres a million threads on the tank cracked.

no heat : "the common" reasons, either the system still isnt full (air bound) or w/ all the
messing around w/ running hot the "new" thermostat is now damaged. if the coolant
isnt circulating (stuck t-stat) you will have poor/ no heat.

there's endless possibilitys, but fix what you know is broke 1st, then move on. also
continued "playing around" w/ overheating will eventually damage the engine.

 

understandable. i mean, now i'm going to replace the tank, and i'll order a new thermostat. might as well replace the radiator cap. and the water pump is next on the list right before the fan clutch.

the car only 'over heated' twice and no smoke was present at all. when i idle it with the radiator cap off, temp reads fine. even though i can replace everything myself, this is going to be a $500 tune up.

on a side note, i'm pretty sure coolant is circulating, all the hosing, including the thermostat housing, get very hot after awhile. if it wasn't moving around, i'm sure these wouldn't get that hot.

 

tank is sealed with a high temp silicone. new thermostat/gasket and radiator installed. took about half a gallon of coolant. now it seems good. havent driven it hard yet. i fear the water pump needs to be replaced. and the fan spins very slowly, but AC and Heat works great w/ no overheating yet.

 

Sounds like you fixed the problem. I'd drive it around and see if it overheats still. If it doesn't, then you've fixed the probelm. If it still does then its probably the water pump going out.

 

curious, how did the radiator look? possibly clogged restricting the flow?
Sounds like you got it, a/c on usually heats things up quick.

 

drove it today for a 15 min drive and everything is ok. it still makes a weird 'bearing' noise. but no overheating. i'm hoping i didn't hurt anything, but everything seems fine, no smoke. radiator looked ok to me, i didn't notice any leakage / spots on it where it might be clogged.