One manifold hotter than other

[Ralph 123]

I just replaced the manifolds, risers (3") and elbows on my cousin's 97 Merc 5.7L. The manifolds and elbows are AP, the spacer is Osco because they were out of APs.<br /><br />The starboard elbow feels significantly warmer than the port elbow. Port is cool to the touch and the starboard is warm/hot with the engine fully warmed up and running at 160 degrees.<br /><br />Any ideas why I am seeing such a difference and should I be concerned?

 

[crazy charlie]

Re: One manifold hotter than other

Ralph,did you use any type of gasket sealant on the riser to manifold gasket????Charlie

 

[Ralph 123]

Re: One manifold hotter than other

Nope - dry per instructions....

 

[Haut Medoc]

Re: One manifold hotter than other

Is this sea water or fresh water cooled?

 

[Ralph 123]

Re: One manifold hotter than other

Raw water. Good flow. Engine temp stayed right at thermostat rating of 160 for an extended period at slow idle. I should mention this same condition existed to a larger extent with the old manifolds, spacer and elbow. That is, Starboard was very hot while port was cooler. They were pretty rusted up so we replaced them at the right time.

 

[Haut Medoc]

Re: One manifold hotter than other

If you are raw water cooled, you should have a 142 degree stat. If you can't hold your hand on it for awhile that a'int right. I would change t-stat for starters. Unfortunately RWC motors don't last nearly as long as FWC. If you're running in salt water so much the worse. For the price of a gasket I would pull the riser & see if it's restricted by engine scale.J

 

[crazy charlie]

Re: One manifold hotter than other

Sealant is sometimes the culprit but not in your case.Did you check the exhaust shutters????Could be broken off and in the bottom curve of the Y-pipe restricting the exit of water....Charlie

 

[Ralph 123]

Re: One manifold hotter than other

Merc Spec for 1997 with this S/N is 160 thermostat P/N 807252 2. <br /><br />The manifold, riser and elbows are brand new. No obvious rstriction seen in the block ports during removal and replacement.<br /><br />Edit: CC you read my mind. I checked the port shutter but not the starboard. I wanted to see if anyone else confirmed my hunch...<br /><br />edit 2: Cousin says he checked the flap and it was working and did not look damaged....

 

[crazy charlie]

Re: One manifold hotter than other

Should be able to get a look with just removing the rubber.Charlie

 

[QC]

Re: One manifold hotter than other

What about the thermostat housing? You could have a restricted outlet to the starboard side. Couldn't you just run it for a few seconds with both hoses removed at the manifolds and see if you have reasonably even flow through both hoses? That would eliminate supply from the equation, right?

 

[Ralph 123]

Re: One manifold hotter than other

That's my next step Quietcat.

 

[Bondo]

Re: One manifold hotter than other

I Really Don't think you've got a Problem, Ralph.........<br /><br />They Never run the same temps.........<br /><br />Unless it Hurts to hold on to that riser,.........<br /><br />Just Go Boating,.............. <br /><br />My 1st Splash of the season is Saturday..........

 

[Ralph 123]

Re: One manifold hotter than other

Bondo, I can hold it there but not with ease like I'd expect with brand new stuff... I wouldn't be too concerned if the difference weren't so big. Well, for peace of mind I'll go the next step.<br /><br />Have fun Saturday!

 

[cc lancer]

Re: One manifold hotter than other

My starboard side riser has always run warmer than the port, when I am idling on the muff.<br />It has got to be something to do with the thermostat housing. Out on the water, it evens out. <br />Rather than take the pipes loose, you can "feel"<br />the pins for the shutters, and with a light you can check to see it they have been spinning. This would indicate, part of it had broke off.

 

[yoced]

Re: One manifold hotter than other

Ralph if you are worried about it, switch the risers. If the problem follows the risers then you brand new parts are bad. If the problems stays where it is then Bondo is right again, and you can at the very least relax while you take your time figuring how hard you want to pursue the temp difference.

 

[llerrad]

Re: One manifold hotter than other

You might be looking for problems when there is none. I have the same thing at idle left side riser cool right side hot (I can hold my hand on the riser but is is hot) riser cools with higher rpm, I thought it was a problem but it's been running for 20yrs I belive I was thinking too much, the fact I can keep my hand on it I know it's Ok.

 

[Ralph 123]

Re: One manifold hotter than other

I ain't that worried yoced! forgetaboutit <br /><br />I think I'll pull the thermo housing and throw a new thermo in, test it and declare it sea worthy!<br /><br />I run twin 5.7Ls and this temp difference is bigger than on either of my twins which is why I was a bit concerned. But, like I said, it was like that before the replacement too and she ran fine.

 

[achris]

Re: One manifold hotter than other

You will get a difference because the water will flow out of the thermo housing to the side with the least restitance, the other side will get hot. Once you get on the water the back pressure on the exhaust will even out the water flow and thus the temperature. When you crank it up you'll not even be able to feel any difference.<br /><br />Chris..............

 

[achris]

Re: One manifold hotter than other

How'd that happen? (Double post)