New thermostat no bypass hole

[Wmsproul]

Purchased new thermostat kit from Sierra 18-3677. Seems to be the exact replacement for the original except there is no knot here cut for a small bypass of water. I know this is not inline with system but opens and lets the hot water out and cooler water to circulate. So is the hole necessary?

Back story(short version), apparently ran raw pump dry, pulled tstat housing when flush all hoses and engine. No pieces of impeller anywhere except pump hose. Thought I would replace tstat since I was there.

 

[alldodge]

Depends on what thermostat housing. If the housing has a bypass port built in then its not needed. Looks like the PO modified the stat, don't see that being factory

 

[Wmsproul]

Is the bypass port easy to see in/on the housing?

 

[Wmsproul]

Don’t see a bypass inside the housing but it does have the port that goes around the fuel jacket and out the port side exhaust riser. Could this be considered the bypass? The tstat housing part number is 3850471

 

[alldodge]

Should be, might also be able to figure it out if we knew what VP motor it is

 

[Wmsproul]

Ok it looks like it has a bypass inside the thermostat housing this is from the inlet to what would be above the tstat. Chased it with a zip tie to make sure. So I assume this new thermostat should be fine.

 

[Wmsproul]

Ya my bad it’s a 5.0Gi feps

 

[alldodge]

Looking at the system I don't see it being needed, but it also would not hurt

http://boatinfo.no/lib/volvo/manuals/5057a-f.html#/214

 

[Fun Times]

Maybe try googling the OEM part number in/on "EBay" to maybe see some up close photo images of the OEM thermostat to see if it has that cut out like yours has.

It's at least good that you now know that bypass in the housing is clear of debris because usually if it gets clogged it will swell and burst the U shaped water hose between the pump and T/housing.

Make sure to check the U hose periodically for excessive swelling and hardness while running the engine or at least until you're comfortable using the aftermarket thermostat.