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5.7L overheating only at idle..........where to turn?

when the boat is sitting in the water, with its normal load, is the HX cap the highest component in the cooling system (vs the hoses from the exhaust manifolds)?
 
I don't think so MakoMark. I believe it is the exhaust manifold hose, which is why I mentioned putting a double-ended barb in it to fill and purge from. The engine sits at angle to mate with the prop shaft, lowering the heat exchanger from the start and the replacement hose I used curves up as it come out of the manifold to clear the lifting eye. I will double check tomorrow though.

Thanks.

makomark said:
when the boat is sitting in the water, with its normal load, is the HX cap the highest component in the cooling system (vs the hoses from the exhaust manifolds)?
Click to expand...
 
if that's the case, then you will have a tough time getting all the all purged out of the cooling system....

You may want to see if you can connect a vacuum pump to the heat exchange, on the coolant side.....many years ago, I had the pleasure to replace a power steering hose on a Ford minivan....afterwards, the PS pump howled like a coyote due to trapped air....the old school approach failed to purge the air....the solution was to apply a vacuum pump to the reservoir with the engine running....I was amazed when the howl dissipated as the vacuum increased...just a thought..
 
Thanks for the suggestion. I just Googled and found a product called "Airlift 55000". If the new sender doesn't work, I'll put one on the engine and see if that fixes things. I've been trying to figure out how to get the air out of the high points.

makomark said:
if that's the case, then you will have a tough time getting all the all purged out of the cooling system....

You may want to see if you can connect a vacuum pump to the heat exchange, on the coolant side.....many years ago, I had the pleasure to replace a power steering hose on a Ford minivan....afterwards, the PS pump howled like a coyote due to trapped air....the old school approach failed to purge the air....the solution was to apply a vacuum pump to the reservoir with the engine running....I was amazed when the howl dissipated as the vacuum increased...just a thought..
Click to expand...
 
If this air bleeding thing continues to be a problem, would you consider installing small 1/8" TP bleeder petcocks at these troublesome areas???

Once the cooling system has been purged of air, and when the H/E coolant recovery system is working correctly, you'd have no future issues!


.
 
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Yes. That was my first thought actually in one of my earlier replies. I had thought of tapping a double-ended barb for a small copper riser/cap for bleeding and filling. I was going to install it on the highest hose point. Then I found out about the vacuum method of putting the coolant in the system, which seemed like it would do everything a bit easier.

Any suggestions on removing the coolant already in the engine if I go that route? I'd like to be able to suck it all out as I cannot capture it in a bucket as the engine compartment is way too tight. I dumped it to the bilge last time and then captured it at the garboard drain but that wasn't ideal.

RicardoMarine said:
If this air bleeding thing continues to be a problem, would you consider installing small 1/8" TP bleeder petcocks at these troublesome areas???

Once the cooling system has been purged of air, and when the H/E coolant recovery system is working correctly, you'd have no future issues!


.
Click to expand...
 
clbme,

In your first post you said "I changed out all of the closed system cooling hoses". Did you use Crusader preformed hoses or just standard by the foot hose? Some of those hoses going across the top of the engine just don't look right to me.

Erich
 
Hi Erich,

I used standard wire reinforced hose from a local marine shop in town which is why they don't look stock.

erich said:
clbme,

In your first post you said "I changed out all of the closed system cooling hoses". Did you use Crusader preformed hoses or just standard by the foot hose? Some of those hoses going across the top of the engine just don't look right to me.

Erich
Click to expand...
 
For anyone following this thread or has a similar problem I wanted to follow up. After studying the engine for a bit I reasoned that any trapped air would be in my port return hose from the exhaust manifold as it is the highest point in my closed system loop. I decided to install a T at this point to fill/purge any air in the system. I made the T using a couple of hose barbs, a T, and a plug. I drilled and tapped the plug for a thermostat drain. As thought, when I cut the hose to install the T there was indeed air at that point.

When I refilled the system with coolant, I used the Lisle burping funnel with an extension to be sure I was higher than the installed T, as well to to create a little head to help purge any air. I've run the engine a few times now, burping the large pockets of air through the funnel. Once I shut down, I open the installed drain, purging any air until I get a solid coolant flow. I've done this three times now, each time finding air. After the last shut down of the day I let the engine cool down fully and found that the coolant in the funnel had drained completely back into the system.

Temps now are encouraging and pointing in the right direction. I'm reaching 180/5 at which point the temps drop back to the 170's when the thermostat opens. I'm still able to increase the rpm's and get a further temp reduction leading me to think there is still trapped air, however, I'm optimistic that this will ultimately solve my problems after several more attempts to purge the system.

Thank you to everyone that replied with suggestions and help.

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I see that you used water pipe components.
Normally I'd suggest against this, but I also see what appears to be two reduced hose nipples that may be 1" at the pipe threads.

Cool! :D


.
 
Hi Rick,

Thanks! Yes, the i.d. of the hose is 1.25", however, the nipples flare to the T which is 1.5" IIRC. It's cast iron. I opted out of bronze as I wasn't sure it would work. I'm curious as to why you recommend not using them normally.
 
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clbme said:
Hi Rick,
I'm curious as to why you recommend not using them normally.
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The steel, brass or bronze water plumbing fittings are typically rough in the ID, and are a bit restrictive.
Whereas the Marine grade fittings are much more smooth, and less restrictive in the ID.

I think that with yours being somewhat over-sized, you'll be OK.


.
 
RicardoMarine said:
The steel, brass or bronze water plumbing fittings are typically rough in the ID, and are a bit restrictive.
Whereas the Marine grade fittings are much more smooth, and less restrictive in the ID.

I think that with yours being somewhat over-sized, you'll be OK.


.
Click to expand...

Hi Rick,

Thanks for the reply. I hadn't even considered that, but I will remember it for sure.

I was able to run the engine today for a bit and after about twenty mins/half an hour at idle and then a few minutes bumped to 1000 rpm I'm happy to report that the temp didn't cross 160! I will run it a few more times on the hose to be sure it continues to check out, and then we plan to get a few beautiful fall days in on the river to shake her out. Hopefully, then we'll have a full season next year.

Thanks again.
 
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