Volvo Penta 2003 thermostat closing bypass

[patpin]

Is this the correct thermostat. I cannot imagine how it can completely obstruct the bypass. Or are the coils of the spring partially obstructing the bypass?

[skipperpete]

The freshwater cooled engine and the raw water cooled engine have physically different thermostats[ATTACH]

[deblen]

This may help:
http://coxeng.co.uk/wp-content/uploa...hot-water1.pdf

[patpin]

Originally Posted by deblen

This may help:
http://coxeng.co.uk/wp-content/uploa...hot-water1.pdf

Link doesnt function.

[patpin]

Originally Posted by skipperpete

The freshwater cooled engine and the raw water cooled engine have physically different thermostats[ATTACH]

It is a freshwater cooled version. What do you think of my thermosat. No inscriptions.

[Pete7]

Originally Posted by patpin

It is a freshwater cooled version. What do you think of my thermosat. No inscriptions.

Well, first check is to drop it into a pan of very hot water and see what happens. If you have some way of measuring the temperature and comparing it to the specs from Volvo that would be good.

As to condition, doesn't look too bad. We have the raw water cooled version which eats thermostats over time due to the different metals in the thermostat and engine etc.

Worth carrying a spare one btw.

Pete

[patpin]

Originally Posted by Pete7

Well, first check is to drop it into a pan of very hot water and see what happens. If you have some way of measuring the temperature and comparing it to the specs from Volvo that would be good.

As to condition, doesn't look too bad. We have the raw water cooled version which eats thermostats over time due to the different metals in the thermostat and engine etc.

Worth carrying a spare one btw.

Pete

I have done the test and it opens at 75 and is fully open at 84°C but my question was: how does it closes the bypass. There is no disc or something similar.

[skipperpete]

As a guess I’d reckon that with the raw water version the raw water is diverted by the bypass disc with no reduction in flow to cool either the exhaust or the engine or both but the heat exchanger version has less or no need to close the bypass, its always open...just a bit slower to warm up and maybe/probably less efficient under load

[deblen]

Originally Posted by patpin

Link doesnt function.

Try this & click on freshwater cooling link on last Volvo pic


Calorifier installation – Cox Engineering

[deblen]

The 2 types of t-stat used in 2000 series.
The silver colored one is for fresh water cooled.
It has a "foot" sticking out that closes the engines warm up coolant path.
https://www.parts4engines.com/volvo-...03-thermostat/

[patpin]

Originally Posted by deblen

The 2 types of t-stat used in 2000 series.
The silver colored one is for fresh water cooled.
It has a "foot" sticking out that closes the engines warm up coolant path.
https://www.parts4engines.com/volvo-...03-thermostat/

Thanks, mine ressembles the raw water one (wrong) because the is no foot closing the bypass opening under the termostat housing.

[patpin]

Originally Posted by deblen

Try this & click on freshwater cooling link on last Volvo pic


Calorifier installation – Cox Engineering

thanks fr link.

[patpin]

Originally Posted by skipperpete

As a guess I’d reckon that with the raw water version the raw water is diverted by the bypass disc with no reduction in flow to cool either the exhaust or the engine or both but the heat exchanger version has less or no need to close the bypass, its always open...just a bit slower to warm up and maybe/probably less efficient under load

A lot less efficient probably (when the wrong thermostat is open),because the circuit over the bypass tube is 1/shorter and 2/there is no resistance from the heat exchanger. On the other side, I guess the circulation pump is seroiously overdimensioned in order to be able to cool when at low RMP. I do not find any data on its flow rate at diff. RPM's

[skipperpete]

Originally Posted by patpin

A lot less efficient probably (when the wrong thermostat is open),because the circuit over the bypass tube is 1/shorter and 2/there is no resistance from the heat exchanger. On the other side, I guess the circulation pump is seroiously overdimensioned in order to be able to cool when at low RMP. I do not find any data on its flow rate at diff. RPM's

Not really, the heat rejection at low rpm is minimal. One of the reasons I posted the pic of the two thermostats was also to point out that the temp ranges are quite different, low temp for seawater cooling with bypass blocker, higher temp and no bypass blocker for heat exchanger cooling

[deblen]

VP 2002/3 thermostats & cooling system.
I finally found this info that I had copied from another poster in the past.
Hope it helps

Plug T-stat bypass Test.PNG Views: 43 Size: 23.5 KB ID: 274385" style="margin: 2px" />