overheating after new manifolds and risers

[mr.bobdobalina]

Re: overheating after new manifolds and risers

update--flushed the block through the circ pump holes (no blockages). replaced the circ pump. still overheating.

reanalysis--

this engine worked fine albeit with corroded manifolds and risers. So i changed them. Now it's overheating.

Everyone unfamiliar with engines says, oh you did something wrong. Makes sense. but what could i do wrong installing manifolds and risers that would cause risers to overheat at low rpms?

If they were leaking air, could that cause low rpm overheated risers? to 220 degrees? And then open throttle up to 3k rpms and they cool down again?


1) anyhow gonna remove them and double check the gaskets and connection.



2) after this, new raw-water pump, and or new serp belt, not seeing any slippage but noticed the engine is squeaking from the belts or pulleys or something. anyone know if that symptom is a clue to something.



--other symptoms and history.
starter sounds tinny and engine only starts with throttle opened a bit.
belts squeaking.
engine was fine till exhaust risers and mans were replaced.
low rpm overheat at risers, but thermostat housing (temp gun) stays in normal range
new impellar, new circ pump, new thermostat, new hoses, new clamps, raw water line from drive has good flow in both directions, new manifolds, new risers. had volvo tech spend 3 hours on boat, didn't solve it.


new to owning boats, this is supposed to be fun right?

 

[tkrfxr]

Re: overheating after new manifolds and risers

I would be very suspicious of an air leak....even if you don't see it on a clear hose....

Do you have a flushing system, like NeutraSalt?

Does the engine have a fresh water hose adapter for flushing?

Does the outdrive water hose appear intact?

Is the transom water connection intact? Clamps are tight and hoses intact?

I had a recent experience with an air leak and once I closed it, things were back to normal...

http://forums.iboats.com/showthread.php?t=430405

The NeutraSalt system is NOT in the engine manual's cooling diagram!

 

[mr.bobdobalina]

Re: overheating after new manifolds and risers

Thnks tkrfxr. You're either or heart md. or you work on clocks

Your thread is very similar to mine. Same symptoms. I did the clear hose test and didn't see bubbles. I don't have a neutra salt system. I double checked the freshwater flush line, and new clamps as far as the eye could see. Will go thru it all again.

Also, checked the flow at idle by disconnect the hose at tstat housing. Manuel says 2-4 inch stream. I'm getting 1/2 inch drool. Ahah. Finally a lead in the case.

So either i'm plugged thru the drive somewhere
i'm sucking air
or the raw water pump is bad. Squeels like crazy.

Time is money so I'm putting a new pump in first. Then We'll haul it out and go thru the intakes on the drives up thru transom and see whats clogged.

Thanks Again.

 

[skydrol]

Re: overheating after new manifolds and risers

Just a thought, last week I got an overheat alarm while at low cruising rpm. Higher rpm, no alarm and at idle no alarm. Checked the indicators - water temp ok and oil pressure and temp were good. Popped open the cowl to take a look around and saw a slight flat spot on the 3/4" hose that runs from the intake manifold to the riser. My suspicion was confirmed when running the motor, the hose did not open up under pressure but collapsed more when the rubber heated up with engine temp. I changed the hose and the problem was resolved, 10 hours on the engine since then and hasn't come back.

So, how old are the hoses and how are the bends in them? Are any of them collapsing while running?

 

[mr.bobdobalina]

Re: overheating after new manifolds and risers

not a bad idea to check hoses.
replaced the sea water pump today. still alarming at idle.
so now we have new everything but overheating. circ pump, thermostat, raw water pump, manifolds and risers.

but this engine didn't overheat till i started working on it. so i think it's a hose, or an air leak from me being clumsy with the heavy manifold. pulling on things and having it rest on things. I saw one thread where a guy was pulling air from a faulty one time hose clamp. I still have a couple of those that i should replace on the sea side of the engine.

the other thing to investigate is the drive. gonna check how it runs on flush connector and see how she runs. shouldn've done that much sooner i know.

at least the sea water pump doesn't squeak anymore.

we'll see tomorrow.

 

[c.fish]

Re: overheating after new manifolds and risers

I'am overheating as well. Merc. 5.0 Xl, 1989. I'v had a closed system for past 8 ys Originly in fresh now in salt. I get sea water flow to exchanger and out. I took of hoses that connect to risers and feel exhaust coming out of both left and right risers. Before I replace risers could there be blockage after risers? If so where?