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Thermostat weep hole


edb150
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 I changed the stat in my 96 427 today and I feel like a dummy because I forgot about the weep hole. it was 95 plus in Illinois today and I was out in the sun so my brain wasent in top shape. whats it there for and whats gonna happen? im chasing an overtempt issue when the trucks loaded and its over 90 out. first thing I did was replace radiatorbut that dident help. I replaced the t stat, coolant filter , and the bypass valve. condenser and cooler clean of debris. truck pulls a dump trailer so I clean it often. seems to run cooler with new stat  but I haven't driven yet now im wondering about the position the weep hole is in. any help would be appreciated

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starts goin into red and have to back off. gauge is correct/ when it gets hot I get black smoke out the pipe. haven't let it overheat. at cold start it was at 195 within 15 to20 min at idlen ow with the new stat its 160 hoping its fixed

 

Edited by edb150
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did you check the water pump to see if its pushing water? if its moving water and the belts are tight next. pressure test the system to see if you have a bad head gasket pushing air into the coolant? you would see soot and bubbles in the coolant.

 

the weep hole is to allow air to bleed out of the system. it also helps keep the t-stat housing always full of water so that the t-stat will open and close at the correct temps. some t-stats have a small hole drilled in the ring. others may have a check ball. the reality is I have never noticed a car overheat because of the weep hole location. once the T-stat opens it lets out any air and the turbulent water should carry any air out of the housing.

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10 hours ago, edb150 said:

starts goin into red and have to back off. gauge is correct/ when it gets hot I get black smoke out the pipe. haven't let it overheat. at cold start it was at 195 within 15 to20 min at idlen ow with the new stat its 160 hoping its fixed

 

Hows your charge air cooler any boost leaks? shouldn't have black smoke under load unless your lugging it! an over fuel /lack of air situation may be causing this issue ! also if you have a viscus fan are you sure its working correctly?

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fjk you may be on to something there is some sort of exhaust leak sound like at the back of the motor when its under load.  its been there a while but its worse now. If I remember right I had a mack tech tell me about a pipe on the back of the motor. is there a pipe from the manifold to the compressor?

Edited by edb150
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