Correct installation of thermostat?

[Johnlink]

Hi All

I have a 1985 GM/Mercruiser 5.0L raw water cooled. Replacing the thermostat (and housing) but have come up with two completely different assembly methods for the thermo and sleeve and sealing rings. Please check the attached diagrams and can you confirm A or B is correct?? Also my T Outlet did not have any poppet valves fitted (has run for 15 years without) and they are no longer in stock - so is it totally necessary to have them? Guess they limit the leg impeller pump from pushing too much cool water up to the elbows at the expense of the circulation pump. Down side could be when they disintegrate with age and end up blocking your plumbing at the elbows? I know this style of thermo housing is no longer in use from 30 years ago, but maybe some with older Alpha1 era boats out there could know the answers.

Many thanks

 

[achris]

This is lifted from the genuine Merc service manual on your engine...


Chris........

 

[achris]

To clarify. A is from the service manual, B is a parts breakdown drawing not an assembly manual.

 

[tailwind 67]

I just ran in to this. If you go with B, the brass sleeve sticks up above the housing, and the top will not set down unless you eliminate the gasket under the thermostat.
The correct order is A, with the turned in lip of the sleeve at the top, and the gasket sitting on that. I am just not sure what the stainless steel separator plate between the two gaskets under the housing cover is for. I don't have one.

 

[tailwind 67]

2nd reply entered in error

 

[Johnlink]

Hi tailwind 67 - thanks very much for your reply to my old question on thermostat housing assembly order. I have tried both A and B and at this stage my engine is still overheating (original problem see my other post) with no water flow off to the manifolds all water flows off to the elbows only. I have fitted clear hoses to help in seeing the water flow. Do you by any chance know if the circulation pump forces water in to the block or just circulates it around the block?

 

[76SeaRay]

The element (I think you were referring to it as the brass sleeve) always goes into the engine so that the hot engine water opens the TStat by heating that element. Are you sure you aren't getting an air lock that prevents the hot engine water from heating the element? Many new thermostats come with a tiny hole in the ring to allow air to escape through the lines. Other TStats most people drill a small hole (about 3/32 to 1/8 inch) to prevent the airlock. Lots of online links to this issue from car and truck owners.

 

[tailwind 67]

I just came in from my garage where I was trying different assembly orders of the housing sleeve and thermostat. I have decided to go with the gasket on the bottom under the thermostat, then the thermostat, then the brass sleeve with the turned in lip at the top. If the brass sleeve has the lip at the bottom, it will not sit in the housing all the way.
I have read and seen in some pics where the thermostat is on top of the brass sleeve with the gasket between as I mentioned in my first post. If you look at it in either configuration, the same result will be achieved. The water is still closed off except for the bypass port when the thermostat is closed, so I decided to go with what makes the most sense in the build up.

 

[76SeaRay]

Pictures? Looks like I misunderstood about the sleeve. Thought you were talking about the TStat.

 

[tailwind 67]

This is my housing and the brass sleeve, thermostat and gasket. I have the thermostat in two different configs. On my last build I had the brass sleeve with the lip on the bottom and the thermostat underneith, but no gasket as with one, the brass sleeve protruded above the hole preventing the cover from going on. Note this is a different style housing then the one with the plastic sleeve. I had one of those housings once.

 

[Colsanders1955]

I had to buy a new housing and thermostat for my 1988 MC 5.7L. Two things: The old housing has a bolt twists off so I could get it off and disassemble it (along with the old intake). Instead of spending 300 bucks for a used replacement, I got this newer one. 1st. It has no brass sleeve, only a plastic one that sticks up too high for the cover to close. I assume the thermostat goes near the top and not right into the intake(?). Not seeing what secures it in place. Secondly, the old one had a rod with two spring loaded check balls. The new kit didn't come with these. Not sure what they do. Pic of all parts they sent me attached. Thanks