Thermostat Housing

[wkb2460]

I have a 2000 Volvo Penta 5.0 Gi, I went to replace the thermostat, as the
engine was running cool.
When I opened the housing, I found the thermostat wedged into one of the hose openings, it was not secured into position with an O ring as the manual states it should.
The area where the thermostat should go is rusted and it will not stay in place with the O ring. I have ordered a new housing, is this a common problem with this model.

It is a lousy design.

 

[Don S]

Re: Thermostat Housing

Nope, not a common problem.

 

[wkb2460]

Re: Thermostat Housing

any idea why the thermostat became dislodged from the housing?

 

[Bondo]

Re: Thermostat Housing

any idea why the thermostat became dislodged from the housing?

Ayuh,.....
Improper Installation would be My Guess....

 

[wkb2460]

Re: Thermostat Housing

I just purchased the boat, so I did not do the installation,
However, its not a hard job to put an O ring on to secure the thermostat in place.

 

[Bry21317]

Re: Thermostat Housing

I am not sure if the Merc is the same as the Volvo. On my Mercruiser 5.0 I have an Oring below the Thermostat, does not hold it in place, and then about a 1-1.5 inch gap above the thermostat where a Spacer goes. This is what actually holds the thermostat in place, so you might be missing a part.

I am sure one of the guys here can tell you if yours should have this or not, and give you a diagram of it.

Hope this helps.

Bryan

 

[JustJason]

Re: Thermostat Housing

Are you saying the intake manifold is corroded where the tstat goes?
Post a picture if yuou can.

 

[wkb2460]

Re: Thermostat Housing

No, The Thermostat housing is where the thermostat mounts.
It is corroded and there is no lip inside for the O ring to retain the stat.
I have all the schematics from Volvo's web site and I am sure there are no parts missing.

It is a lousy design. Most stats that I'm familiar with sit in a groove in the manifold and the housing just kinda covers it. With this engine the stat hangs from inside the housing via the O ring.

 

[Maclin]

Re: Thermostat Housing

If you are comparing the theromostat's location to a car's cooling system, well, you can't. The thermostat housing on your boat's engine has a pivotal role, lousy design or not. It has to make enough water available to the engine's cooling circuits as needed while maintaing a path for the raw water coming in to bypass out the exhaust if it is not needed. It is easy enough to call it a lousy design if the system is not understood.

Lousy mechanic or lousy design? Count up the Volvos in service today that cool correctly, I think the results would point to a lousy mechanic prior to you arriving on the scene.

Boat systems need yearly attention in almost every area to defray the effects of corrosion.

 

[Lou C]

Re: Thermostat Housing

That vintage Volvo uses the same thermo housing as OMC Cobras, in fact they are the same part # in some years. It must have seen a lot of salt water use for it to get that corroded. I have an original one that was used in salt that was starting to get some flaking corrosion on it so I replaced it in 2003 and it's been run 4 seasons since in salt and does not have any heavy flaking corrosion yet. The design with the retaining rubber ring works well for holding in the thermostat, the only issue is that if it does get heavily corroded it can be a little hard to pry out the rubber ring. I replace thermos each season in salt water.
I like this design because it's simple, I put some OMC gasket sealer on the threads of the thermo housing and they come right out with no issues.

Must have someone working on it that didn't know how the 'stat was retained.

 

[Don S]

Re: Thermostat Housing

Must have someone working on it that didn't know how the 'stat was retained.

You mean like a previous owner without a manual or a clue???

 

[bruceb58]

Re: Thermostat Housing

The lip on mine is getting corroded enough to the point where the o-ring has less of a lip to sit on.

It could be that yours has corroded enough that the area where the o-ring sits does not have enough material left to hold the o-ring against the thermostat anymore.

 

[wkb2460]

Re: Thermostat Housing

thanks for all the info, I put the new hosuing in today and everything is working fine. I have an electrical question that I be posting.