Temperature issue

[Doc Holiday]

Coolant flow is like electrical currents, taking the path of least resistance. By opening the hot water valve the coolant may flow preferentially through the hot water tank circuit resulting in reduced flow through the engine circuit. Is the hot water tank flow after flowing through the engine?

 

[Distant]

It seems the actually temperature of the coolant in the engine is around 200.
Normally guage reads 180,however when I open valves for the hot water tank,guage will read 200 the actually temperature. The location of the sensor is not giving true temperature normally,when opening valves and get coolant flowing pass sensor it reads more accurately. I will now contact the shop that reconditioned engine and discuss with them I feel 200 is to high.

 

[Distant]

Also ,answer to other question...There is an outlet at top of recirculation pump to connect hot water tank and return on rear of engine where sensor is,,so recircs coolant through engine and tank at same time.

 

[bligh]

It seems the actually temperature of the coolant in the engine is around 200.
Normally guage reads 180,however when I open valves for the hot water tank,guage will read 200 the actually temperature. The location of the sensor is not giving true temperature normally,when opening valves and get coolant flowing pass sensor it reads more accurately. I will now contact the shop that reconditioned engine and discuss with them I feel 200 is to high.

Did the shop install a new thermostat?

 

[twistedtree]

Get an IR temp gun on the tee where the sensor is located, and get a second opinion on the actual temp both with and without flow to the HWH.

I believe the sensor is actually experiencing different temps based on coolant flow or not. But worth confirming what to actual temp is. Your gauge could just be off, and you have no other problem.

 

[menzies]

This might be too simple a thought.

Is your coolant overflow tank full? When you open the valve to move the coolant through the hot water tank it will reduce the amount of coolant in the engine, which needs to be replaced by the fluid in the overflow tank.

 

[Distant]

Will discuss hopefully all issues with the shop that worked on the engine,thermostat, gasket????
Yes plenty of fluid in tank.
Thanks.

 

[boatruptcy]

I think Menzies is onto it. Have you tried opening reservoir when engine is COLD, starting up with valve closed to tank, then gradually opening. Check reservoir as it runs for a few minutes. If your tank remains at same level, you are full and no air lock (usually). Good luck.

 

[Distant]

Did run the engine with cap of for 45 mins to an hour,but will do again.
Going to take coolant tank of and check thermostat, probably today.
I have hot water tank hooked up to other engine now, working fine.
Thanks.

 

[boatruptcy]

squeeze the hoses as it's running, you can tell if water is pumped through, try with valve closed and then open valve to heater and see if there is a difference.

 

[Barrie]

I had the same engine, 1984. The water was heated via 110volt or heat exchange from one engine. The feed to the hot water system was direct off the engine from the antifreeze reservoir. There was no shut off. Just a 2 foot length of heater hose contented to the hot water tank, with a return hose back to the engine. The engine always ran at between 185-190 degrees, depending on how hard i was pushing it. I thought about putting in a shut off valve for maintenance purpose but it looked so happy i left it alone. hope this helps.

 

[Distant]

Thanks....I just took out thermostat, it is rated at 195f,I am comfortable now,knowing temperature is according to thermostat rating.

 

[Distant]

Just removed coolant tank and removed thermostat,it is 195f,so I am comfortable now knowing temperature is behaving according to thermostat rating.
Thanks

 

[Island Cessna]

Just removed coolant tank and removed thermostat,it is 195f,so I am comfortable now knowing temperature is behaving according to thermostat rating.

Thanks

The 1972 version of the Perkins marine engine install manual says at Section D1 “the operating temperature of the closed water system at the outlet should be in the region of 190 deg F”.
In the final sign off inspection for the install they quote 200 deg F as the maximum coolant outlet temp.
The workshop manual of the same year for the 4.236 Marine Engine states at Sec G12 “For 4.236 marine engines a water outlet temperature in the range of 160 to 190 degree F is permissible” and specifies a thermostat the starts opening between 167 and 176 deg F, and is fully open at 195 deg F.

You should be OK.

 

[Distant]

Thanks much. I did remove coolant tank and checked thermostat,it was 195f. I am ok now that I know the the temp indication is what the thermostat is rated.
Thanks everyone for their input,much appreciated.

 

[Tm Donley]

I am in agreement with Ksceviour regarding air entrapment.
Same as a car or truck, after opening the closed loop cooling system for repairs you always insure the air has been "burped" out of the cooling system to prevent air lock or low coolant.
You have to exercise care when plumbing the water heater to minimize loops high and low to prevent air lock of the closed loop system.
A "T" fitting located at the highest point in the hose loop with a plug will allow air to escape when filling the system.
I had a customer add a crossover valve between the water heater hoses to shorten the flow (path of least resistance) minimizing flow through the water heater.
You want the full flow of coolant to flow through the water heater loop. The crossover valve allows control of water through the water heater with out ever reducing the to the engine. The engine manufacture or a seasoned tech familiar with these engines & systems.
That's my two cents......