NC State Guy
Cadet
- Joined
- Feb 11, 2009
- Messages
- 19
Mercruiser 470, 2 BBL, 1980 model, serial number 5520896
I am breaking in a rebuilt motor and am concerned about overheating issues. The motor otherwise runs fine. The coolant reservoir has had to be refilled twice with 1/3 gallon with less than one hour run total time, 3 20 minute test runs on lake.. No visible leaks around motor and gaskets. After studying some threads, and buying a service manual, here is what I've done so far:
Removed thermostat, checked it in 160-170F water, opens and closes fully. Pressure check coolant system, and reservoir cap at 17 psi, held pressure fine for >2 min. Removed raw water outlet on heat exchanger, rechecked pressure, no leak there, held fine again. Pulled all spark plugs, all show normal coloration. Replaced with new. Ran the motor on muffs at 800 rpm idle for approximately 8-10 minutes, and got these temp readings with IR therm:
Exhaust manifold 164F
Coolant fluid(in reservoir) 140F
Head 200F
Head going into exhaust manifold 229F
Intake manifold 100F
Carb 75F
Fuel lines 100F
I had a big floor fan running on the motor the whole time, and I observed the exhaust fumes they looked ok(barely visible, no white or black smoke) I caught 3 gallons of water from the exhaust it was clear.
The head temp scared me so I cut the motor off and looked for some normal temp readings, couldn't find any. I may be finding normal temps, but I wouldn't know. Just wondering where my coolant could be going. I'm hesitant to run the motor on the water if I'm leaking internally.
My questions:
1. Are these temps normal?
2. Could I run the motor longer to see if the reservoir starts to fall?
3. Is there another method besides taking the motor apart to determine an internal leak of coolant?
4. Should I continue with another test run to see if the coolant drops again?
Thanks
I am breaking in a rebuilt motor and am concerned about overheating issues. The motor otherwise runs fine. The coolant reservoir has had to be refilled twice with 1/3 gallon with less than one hour run total time, 3 20 minute test runs on lake.. No visible leaks around motor and gaskets. After studying some threads, and buying a service manual, here is what I've done so far:
Removed thermostat, checked it in 160-170F water, opens and closes fully. Pressure check coolant system, and reservoir cap at 17 psi, held pressure fine for >2 min. Removed raw water outlet on heat exchanger, rechecked pressure, no leak there, held fine again. Pulled all spark plugs, all show normal coloration. Replaced with new. Ran the motor on muffs at 800 rpm idle for approximately 8-10 minutes, and got these temp readings with IR therm:
Exhaust manifold 164F
Coolant fluid(in reservoir) 140F
Head 200F
Head going into exhaust manifold 229F
Intake manifold 100F
Carb 75F
Fuel lines 100F
I had a big floor fan running on the motor the whole time, and I observed the exhaust fumes they looked ok(barely visible, no white or black smoke) I caught 3 gallons of water from the exhaust it was clear.
The head temp scared me so I cut the motor off and looked for some normal temp readings, couldn't find any. I may be finding normal temps, but I wouldn't know. Just wondering where my coolant could be going. I'm hesitant to run the motor on the water if I'm leaking internally.
My questions:
1. Are these temps normal?
2. Could I run the motor longer to see if the reservoir starts to fall?
3. Is there another method besides taking the motor apart to determine an internal leak of coolant?
4. Should I continue with another test run to see if the coolant drops again?
Thanks