Volvo 5.7gsi running without thermostat

vista_sg · **Joined:** Tue Dec 30, 2014 10:13 pm **Posts:** 19

I had a problem with the water pump recently, and the mechanic who fixed it removed the thermostat at the same time. He said this is normal practice here in Singapore as the heat here means the engines are always running hot so now the sea water will always be running through the engine.

Whilst I would like to believe him, I kind of don't - can anyone confirm that it's ok to run the engine long-term without a thermostat?

deafwish · **Posted:** Mon Mar 23, 2015 1:52 am

Far from ideal on many levels.
Spend the $40 on an OEM thermostat.

crossram · **Posted:** Mon Mar 23, 2015 9:28 pm

it will take longer on warm up. when engine temps reach say the 160 for a thermostat reading, it would be at full open anyway, thermostats are really only for the warm up period

vista_sg · **Joined:** Tue Dec 30, 2014 10:13 pm **Posts:** 19

Thank you both for your replies. I tested the boat yesterday and it runs as normal. Took a little while longer to warm up as expected, but at 3k RPM sits around 160, rising to 175/180 on a 4k RPM run, then straight back down to 160 and below when slowing down to idle.

So I guess the real question is: what are the implications/what potential damage can be done from having the engine spend longer warming up to temp and then having the temp drop below 160 quite quickly.

Note that here in Singapore, heat is generally around 80-93F all day, every day, so sea water temperature is also quite warm.

LouC · **Posted:** Tue Mar 24, 2015 4:55 am

There is no advantage to running without a stat and unless you are on plane it will take forever to warm up. This causes higher fuel consumption (choke stays closed longer) and more contamination of the motor oil. In this case you may have other issues making the engine run slightly hot (160-175 is normal ). In salt water you need to check for clogged risers and if the boat is kept in the water, you can have marine growth in the water intakes. Both will cause mild to moderate overheating as will a worn impeller.

vista_sg · **Joined:** Tue Dec 30, 2014 10:13 pm **Posts:** 19

Some great info there, thank you very much. I have a few jobs to do on the engine at the moment so the thermostat will be replaced before it is run properly again.

ric · **Posted:** Tue Mar 24, 2015 6:54 am

I live in Orlando, FL... Air temps during the summer reach 100 degrees F, water temps are in the low 90s F. Currently right now in March, last weekend the water was 79 and air was 88.

My boat runs a constant 172-175 degrees in all weather conditions at any RPM. If yours is not with a thermostat, you have a cooling problem,

rpengr · **Posted:** Thu Mar 26, 2015 4:48 pm

On my previous boat, I once had a thermostat fail on a two day trip, so I took it out to finish the trip. Without the thermostat it ran fine, but my temperatures were only 120-130deg, even though I am in Florida with 80deg lake temperature and 90deg air temp. I put in a new thermostat after the trip to get the proper 160deg temp.

Short term damage would not be likely, but low operating temperature reduces efficiency, and would not properly evict moisture from the oil & crankcase.

Technologic80 · **Posted:** Mon Apr 06, 2015 8:13 am

Heres how you can easily fix your problem: Find a new mechanic. :wink:

I concur with everybody else - the t-stat NEEDS to be in the engine. It doesnt matter how hot your boating environs is, the thermostat will regulate the temperature properly.

www.iFourWinns.com

Volvo 5.7gsi running without thermostat

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