Bad Water Pump... Signs?

[jmw129]

Hey Guys,

I've replaced the impeller on the out drive and thermostat. Now the engine continues to over heat in idle.

How can I tell if the water pump mounted on my engine is working correctly?

 

[gus-gus]

Re: Bad Water Pump... Signs?

The tell tale should be a full stream, is the only way I know of. I am sure there is a method of checking water pressure in the cooling jacket, but have never read about one or would know what pressures to expect.

 

[jmw129]

Re: Bad Water Pump... Signs?

The tell tale should be a full stream, is the only way I know of. I am sure there is a method of checking water pressure in the cooling jacket, but have never read about one or would know what pressures to expect.

Full stream of water coming out of the water pump if I take the hose off correct?

 

[gus-gus]

Re: Bad Water Pump... Signs?

I am far from an expert, so take my suggestions as such. Just trying to help you.
I believe the hose for the tell tale is from the water jacket, not directly from the pump. The pump could be pumping well, and the thermostat not opening, which would mean a limited flow from the tell tale I think. I would suggest another thermostat.

 

[Fishermark]

Re: Bad Water Pump... Signs?

What are you working on? There is no typical "tell tale" for an I/O like there is on an outboard.

 

[jmw129]

Re: Bad Water Pump... Signs?

What are you working on? There is no typical "tell tale" for an I/O like there is on an outboard.

305 Mercruiser, 230hp, 1985.

 

[81 Checkmate]

Re: Bad Water Pump... Signs?

What did the old impeller look like before you changed it out?

 

[jmw129]

Re: Bad Water Pump... Signs?

What did the old impeller look like before you changed it out?

Little brittle, all intact.

 

[Fishermark]

Re: Bad Water Pump... Signs?

If you are sure the water pump was installed correctly, I would turn my focus to the manfolds and risers - check and see if they are clogged with rust, etc.

 

[jmw129]

Re: Bad Water Pump... Signs?

If you are sure the water pump was installed correctly, I would turn my focus to the manfolds and risers - check and see if they are clogged with rust, etc.

Took off the exhaust manifolds and found the manifold gasket on the passenger side is horrible. Looks like previous owner custom cut their own manifold gasket.

Can a really crappy and I mean really crappy manifold gasket & seal job cause the engine to over heat in idle?

 

[Scott Danforth]

Re: Bad Water Pump... Signs?

do you have an oil cooler? many cases where crud gets stuck in the oil cooler to choke off water flow

 

[jmw129]

Re: Bad Water Pump... Signs?

do you have an oil cooler? many cases where crud gets stuck in the oil cooler to choke off water flow

Scott, I have a 1985 305 Mercruiser V8 SBC engine. I don't know if my engine has an oil cooler. I want to say no.

 

[Scott Danforth]

Re: Bad Water Pump... Signs?

follow the plumbing. there is a line that comes from the outdrive. if you have an oil cooler, it will be in-line. the line then goes to the t-stat housing.

did you do a complete raw water pump, or just the impeller? if you just did the impeller, how were the rest of the parts? I found it best to replace everything.

 

[jmw129]

Re: Bad Water Pump... Signs?

follow the plumbing. there is a line that comes from the outdrive. if you have an oil cooler, it will be in-line. the line then goes to the t-stat housing.

did you do a complete raw water pump, or just the impeller? if you just did the impeller, how were the rest of the parts? I found it best to replace everything.

Just the impeller & t-stat. I now have the exhaust manifolds off. Replacing the bad exhaust manifold gasket.

Can an engine over heat if some of the bad gasket was sucked into the heads or in the engine?

 

[jmw129]

Re: Bad Water Pump... Signs?

Just the impeller & t-stat. I now have the exhaust manifolds off. Replacing the bad exhaust manifold gasket.

Can an engine over heat if some of the bad gasket was sucked into the heads or in the engine?

Scott, I looked and yes I do have an oil cooler. So how do I test / check this part for proper function?

 

[jmw129]

Re: Bad Water Pump... Signs?

follow the plumbing. there is a line that comes from the outdrive. if you have an oil cooler, it will be in-line. the line then goes to the t-stat housing.

did you do a complete raw water pump, or just the impeller? if you just did the impeller, how were the rest of the parts? I found it best to replace everything.

Scott, I looked and yes I do have an oil cooler. So how do I test / check this part for proper function?

 

[Scott Danforth]

Re: Bad Water Pump... Signs?

remove the oil cooler, back-flush it with water. they are straight thru tubes for the water side. I bet you flush out a bunch of stuff.

 

[Fishermark]

Re: Bad Water Pump... Signs?

Can a really crappy and I mean really crappy manifold gasket & seal job cause the engine to over heat in idle?

It isn't the manifold to head connection that is important - it is the manifold to riser connection (and water passage) that is important. Take the riser off the manifolds and post what you find.

 

[jmw129]

Re: Bad Water Pump... Signs?

It isn't the manifold to head connection that is important - it is the manifold to riser connection (and water passage) that is important. Take the riser off the manifolds and post what you find.

Sure will, thank you.

 

[ktbarrentine]

Re: Bad Water Pump... Signs?

Little brittle, all intact.

.... Wow, deja vu... Mine (1990 305) was "a little brittle, all intact, and gave me the same symptoms, until I changed it out. Are you double-dog-dare-ya-sure you got the new impeller installed correctly, with the KEY, and with the vanes pointing in the right direction? Seen each of these errors cause no flow/low flow after the replacement.