Overheating One Cylinder

[wrosales]

I finally had a chance today to test the engine temp with an infrared thermometer. I have an 1992 E90TLEND. I cranked it and it ran good then about eight minutes later I heard the temperature warning horn go off. I tested the temperature of the engine and found these results. On the right side of the motor around the sparke plugs it was in the 190 to 200 range. I then went to the other side and the top part around the spark plug was about 240 and the bottom around 210. Did I run this long enough to cause damage? Why would only one side be overheating more than the other? Shouldn't the temperature be around 160 to 180? Like I said in an earlier post, the tell tale is spitting water but it does not seem continous. It has little breaks in the steam. Thanks for the help.

William

 

[Mas]

Re: Overheating One Cylinder

Water pump may have failed, debris in the line, thermostat could be an issue as well. I would drop the LU and have a look. If you have not replaced the impeller in the last three years, I would replace it!

Temps should not be over 160. Do not run the motor until problem is solved.

MAS

 

[wrosales]

Re: Overheating One Cylinder

Does the water flow in such a way that it gets to the left cylinders last causing it to be hotter than the right side?

 

[wrosales]

Re: Overheating One Cylinder

What exactly do the thermostats do?

 

[emdsapmgr]

Re: Overheating One Cylinder

The whole engine is running hot. It should normally idle at 145 to 155. The hot horn will sound at 212 and will silence when it gets back down to 175. If you don't have a good telltale stream, the water pump could be the culprit. An intermittent stream is an indication of a weak pump. This engine has two thermostats, each controls the head temps in one head. They control the flow of hot water exiting the block into the midsection. If they don't work-it will overheat, despite a good impeller. Make sure they are functioning properly. There is also a pinhole in the thermostat valve body-if it is plugged it will overheat at idle.

 

[wrosales]

Re: Overheating One Cylinder

I think I have to remove the powerhead to get to the thermostats on this motor. Is there an easier way to access it?

 

[emdsapmgr]

Re: Overheating One Cylinder

While a bear, you are lucky you have a flatback model. You should be able to get into the thermostat housing without pulling the powerhead. It will help if you remove the two covers under the lower cowl at the top of the midsection. Then you can loosen the lower cowl, move it downward and you should be able to get to the housing....

 

[wrosales]

Re: Overheating One Cylinder

Ok that sounds good. Thanks very much.

 

[Mas]

Re: Overheating One Cylinder

What exactly do the thermostats do?

Because engines are designed to to operate at about 140 degress. The thermostat's job initially is to limit cooling water around the cylinders until the at proper temp, then open up to allow cooling water ALL around the cylinders once the right temp is achieved.

Inside the thermostat is usually a sealed wax mixture that melts and expands at a certain temp, thus forcing the passage open that was kept closed by a spring.

If the thermostat does not open, the motor will overheat. If it is stuck open, the motor has a difficult time getting up to proper temp.

Of course, crap lodged in the cooling passages will cause an overheat, as well as a failed impeller!

MAS