Struggling with Gauge Temp

[Adammward]

I have a 350 Magnum Alpha (‘91) with open cooling system. Temp has been showing hot 210-240. I changed the thermostat and water recirc pump. I have not changed the impeller yet. All the hoses are cool except the one marked below. Warm water is exiting the exhaust. One side is warmer than the other. I tried backflushing the block. Any ideas?

 

[tpenfield]

You need to backflush the intake line (hose) not the engine block. You may end up replacing the impeller, so don't rule that out.

The hose that is getting hot is the recirculating hose (orange). It sounds like not enough cool water is getting into the engine, because not enough hot water can exit the engine. Hot water has to exit before cool water can enter.

Back flush the intake line (dark blue).
Inspect the T-stat housing for rust and or clogs
Inspect the exhaust manifolds and risers for rust/clogs

Dark blue is the inlet water from the outdrive.
It splits and goes in different directions at the thermostat housing
light blue is cool water to the risers
Orange is warm/hot water recirculating from the top of the intake manifold to the engine block
Red is the hottest water exiting to the exhaust manifolds (and up into the risers).

 

[nola mike]

Also have you checked the temps with something aside from your gauge?

 

[Adammward]

Also have you checked the temps with something aside from your gauge?

I haven’t checked any other way

 

[Adammward]

You need to backflush the intake line (hose) not the engine block. You may end up replacing the impeller, so don't rule that out.

The hose that is getting hot is the recirculating hose (orange). It sounds like not enough cool water is getting into the engine, because not enough hot water can exit the engine. Hot water has to exit before cool water can enter.

Back flush the intake line (dark blue).
Inspect the T-stat housing for rust and or clogs
Inspect the exhaust manifolds and risers for rust/clogs

Dark blue is the inlet water from the outdrive.
It splits and goes in different directions at the thermostat housing
light blue is cool water to the risers
Orange is warm/hot water recirculating from the top of the intake manifold to the engine block
Red is the hottest water exiting to the exhaust manifolds (and up into the risers).

View attachment 369755

This is freaking brilliant! Thank you! I will try this. I don’t know how to inspect the manifolds but can do the rest.

 

[tpenfield]

As for the exhaust manifolds, when the time comes. Take off the lower hose to let them drain. Then remove the bolts that hold the riser onto the manifold and pull the riser off. You will need new gaskets to re-assemble, so get those ahead of time.

 

[Adammward]

What is this tube and the split rubber?

 

[dubs283]

Tube is the lower part of the shift shoe. Rubber piece goes into the output of the water pump housing that mates with the water passage tube into the upper drivesahft housing

The two components pictured have nothing to do with each other

 

[Adammward]

What is a riser and where is it?

 

[Scott06]

What is this tube and the split rubber?View attachment 369775

If that water tube seal is split you wer likely leaking water on discharge side of impeller pump, only would contribute to overheating by dumping cooling water into the exhaust stream and overboard instead of to engine

 

[Scott06]

What is a riser and where is it?

Exhaust elbow on top of exhaust manifold

 

[tpenfield]

Here is a typical exhaust stack, showing manifold, gaskets, (optional spacer block), and riser (aka elbow). The typical flow of water is noted by the arrows.

 

[Bondo]

I have a 350 Magnum Alpha (‘91) with open cooling system. Temp has been showing hot 210-240. I changed the thermostat and water recirc pump. I have not changed the impeller yet. All the hoses are cool except the one marked below. Warm water is exiting the exhaust. One side is warmer than the other. I tried backflushing the block. Any ideas?

Ayuh,..... Welcome Aboard,..... In pretty much any overheat situation, the underlined is where you start, not where you finish,.....