Volvo D6-435 - Lower than expected coolant temp?

[dbsea]

Hi All,

2016 C30-CB. Engine has been running flawlessly, almost 1200hrs on it. This most recent trip over July 4th up to Roche, I was noticing that my coolant temp was LOWER than what I normally see. Typically, once the engine heats up I'm steady at 185 and it never moves. This time, while it did hit that temp at some instances, I was seeing anywhere from 165-185 and seeing more fluctuation than I have seen previously. Anything to be concerned about? TIA!

 

[SKing]

FYI my 2021 D440 runs a consistent 170, now creeping up to 172

 

[Full_O_Fish]

Sounds like the thermostat is sticking open a bit allowing too much coolant flow. While this would be preferred over it sticking closed and possibly overheating, there are still problems associated with under temp running such as incomplete combustion and carbon depositing among other things.

 

[scross]

Hi All,

2016 C30-CB. Engine has been running flawlessly, almost 1200hrs on it. This most recent trip over July 4th up to Roche, I was noticing that my coolant temp was LOWER than what I normally see. Typically, once the engine heats up I'm steady at 185 and it never moves. This time, while it did hit that temp at some instances, I was seeing anywhere from 165-185 and seeing more fluctuation than I have seen previously. Anything to be concerned about? TIA!

Agree with a partially “stuck open” thermostat potentially causing the problem.
I know this is somewhat counterintuitive but low coolant levels can also cause the engine to run under normal temps. Have you double checked the coolant level lately?

 

[dbsea]

Agree with a partially “stuck open” thermostat potentially causing the problem.
I know this is somewhat counterintuitive but low coolant levels can also cause the engine to run under normal temps. Have you double checked the coolant level lately?

I will double check the coolant, and also have my mechanic check the thermostat. Thanks all!

 

[dbsea]

FYI my 2021 D440 runs a consistent 170, now creeping up to 172

Interesting. The standard operating temp for these engines is 185-196, according to the documentation. I will check mine again next time I use it..

 

[dbsea]

Agree with a partially “stuck open” thermostat potentially causing the problem.
I know this is somewhat counterintuitive but low coolant levels can also cause the engine to run under normal temps. Have you double checked the coolant level lately?

The thermostat looks like it might be hard to replace - I can't find any good documentation on where it is and how to do it...

 

[SKing]

The thermostat looks like it might be hard to replace - I can't find any good documentation on where it is and how to do it...

Could the D6-435 be that different in temp from the D6-440? Does anyone else have either of these motors and feedback on their standard temp?

 

[Levitation]

What I am seeing is that a competent and experienced owner is seeing a 10-20 degree temperature drop from what was a consistent 185 under the usual load. This is where the typical recreational boat operator differs. The recreational will rationalize that it doesn't really matter - until it does. The pro will do whatever it takes to identify and correct the issue so that it does not become yet another breakdown - usually at the worst possible time.
To the OP - my advice is to get that thermostat changed out no matter how difficult it is. And if that does not get the engine temp back to the normal level it is time to talk to the engine factory.It may be that the heat exchanger has a leak and is sucking raw water.

 

[SteveCW30CB]

I have the D6-435. It runs at 185 consistently when warmed up.

Steve