1999 sportster - cooling system

[aaronbrooks]

Hey guys, another dude asking cooling questions. This is for the stock 5.7 carb motor. Does anyone have the part numbers for the 160 thermostat and all gasket sets required? I have a small leak at the thermostat housing.

Secondly  I've had this cooling issue for 2 years now and it's time to solve it for good. Temp rises to 160 at normal pace, then bounces around high and back to 160 quickly, almost like it's a ground issue or something. I need to start going through the whole system to find the culprit (assuming it's not the thermostat). I replaced the raw water pump last year, didn't solve it. From what I've read I need to check the temp sensor, all ground wires, and maybe even the circulation pump? I don't know anything about the circ pump. Please help wise ones. 

Edited April 26, 2022 by aaronbrooks

[drh]

Thermostat: https://skidim.com/thermostat-160-degree-r-w-c.html

Gaskets: https://skidim.com/gasket-t-stat-housing-to-intake-gm.html; https://skidim.com/gskt-tstat-cover-gm-indmar-98.html

For your erratic gauge behavior I would first check the cannon plug at the back of the engine and make sure it's connected tightly. I also recommend running an additional thick-gauge ground wire from the negative terminal of the battery to the large stud on the ground bus bar underneath the dash. This helped solve a lot of gauge issues for me. One thing to test is to observe your gauges when you turn on and off accessories - blower, bilge, lights, stereo etc. If you notice them bouncing around or moving higher when you do this it's probably a grounding issue.

[justgary]

1 hour ago, drh said:

check the cannon plug

Indeed!  The Cannon plug on that year should have split male pins.  Gently spread them with a sharp tool such as your pocket knife or a small chisel to make sure they make good contact with the female sockets.  A small dab of grease on them will help keep oxidation away.

The circulation pump is what you would call the water pump on a car engine.  They rarely fail, but can cause temp issues when they do.  Get a marine rated one that has a bronze impeller, not a car one that has a steel impeller.  If you have closed cooling with proper coolant, it doesn't matter which one you use.

[aaronbrooks]

Thanks guys, will attack this shortly and report back anything odd along the way. 

[Woodski]

Also, marine thermostats are specific, they have corrosion resistance that automotive ones do not.  Automotive stats can corrode and will become sticky / stuck.  Your description sounds electrical in nature.