overheating

[henry.blanchette]

Hi all,

I recently had an issue with my raw water system that is finally fixed, but I am still having overheating issues.


full story: ran engine with raw water intake closed and fried the impeller. replaced the impeller retrieved all but one vane, after a small snafu, I now have plentiful raw water coming out of the exhaust.

While I was doing this I decided to replace the engine coolant impeller (it was actually the produce of a mistake but we'll ignore that part). replacement seemed to go fine. I lost about a cup of coolant i replaced the coolant with what they PO had on the boat into the overflow container (light yellow 50/50 mix vs the orange that came out of the pump).

The engine is now overheating after about 5 min run time. I have taken the back plate off of the pump and confirmed the impeller is spinning when the engine turns (friend handcranked while I looked). I tried replacing the old impeller that was working fine, (even though i also removed and compared them and they are identical). I replaced the o ring and cannot see any leaks. My step dad held all the hoses coming into and out of the pump while engine running and said it felt like fluid was moving through all of them (but one - i think the one going from the thermostat to the pump feels cold.

I have also run the engine with the coolant fill cap open (thinking it would depressurize things and help new coolant flow in).

I removed the thermostat to try to rule out thermostat issues and it made no difference.

I wanted to try to disconnect the hose from the pump going to the engine, but i was afraid of losing all the coolant out of the engine and it was really hard to access and wasn't sure what I would do with whatever information that gained me.

When I first opened the back of the impeller after the first time it over heated it sprayed a mist of air and coolant that seemed to be under a lot of pressure. I am afraid that I have done something wrong in the process of trying to refill the coolant. I'm pretty new to engines and learning as i go, so I can never rule out having made a simple but critical mistake. I'm pretty lost at this point. I'm hoping you all might have some ideas. I really appreciate your input. thank you

[henry.blanchette]

I should note, that by overheating i mean it'll hit 200 degrees in 5 min, and it will keep going higher if i let it

[Dave Neptune]

If BOTH pumps are functioning (flowing well) it's time to look at the HX as it may be fouled or plugged.

Dave Neptune

[TimBSmith]

Henry. Suggestion. Godspeed.

I had an overheat event this season. Kelp plugging the feed to strainer and pump. Heat and pressure buildup. I won't get into the water pressure, alarm system and monitoring homework I have been doing.

I have been looking at FWC transition for the past 2 years. I love the indigo and Moyer approaches. Other great approaches documented on this site.

Here is the indigo information, which I include because

https://www.atomic4.com/fwcelect.html

http://www.atomic4.com/freshwater.html

you will find that Indigo includes a pump pressure gauge, which by using, I think you will find invaluable diagnostic data. In fact, I have been considering purchase for RWC flange pump monitoring as well. There is also a great document on Indigo and Moyer system function and installation which now that you own the boat, you will want to be able to think through.

You said a lot in your last post. You changed an HX pump impeller, you located all but a part of the RW pump impeller that failed, pressure buildup during closed seacock episode, you topped off the anti-freeze. That is a lot going on.

-I would like to know actual pressure at both pumps. And use touchless IR thermometer to sample temperatures around cooling system and engine. Inexpensive FLIR could also be useful to look for hot spots as/when/where they arise.

Couple of first diagnostics to bracket assuming both pumps are producing acceptable pressure.
+Is there an obstruction on raw water feed to HX?
+Is there a problem/obstruction within the HX? Raw Water pressure and Antifreeze pressure out of heat exchanger?
+Is there air locked in the system? Bleed entire system. Check pressures.
+Is there an obstruction in the engine cooling system? Step by step including common choke points and water jacket. (The overheat could produce mineral deposits, a vinegar or desalting flush may be in order.)
+You really do want to account for all of the blades of your exploded impeller. If you do not, you will always wonder where it is in your downstream cooling system.
+Read indigo(electronic pump) and Moyer (belt driven pump) installation guides to better understand your system.

Other's will comment further. Again godspeed.

Take care to keep your bracketing of the diagnosis disciplined both the RW and FW systems and the HX system all need careful measurement. You have got this..

[ndutton]

A few highlights in your description caught my eye:

I now have plentiful raw water coming out of the exhaust.

This pretty much eliminates any problem in the raw water circuit.

I think the [hose] going from the thermostat to the pump feels cold.

This suggests the antifreeze is bypassing the block and flowing directly through the thermostat housing. Are you familiar with how the dual action thermostat system works - or is supposed to work? The next quote implies maybe not.

I removed the thermostat to try to rule out thermostat issues and it made no difference.

Unless you blocked the bypass hose as part of this test it did not provide meaningful information.

To me this points to either a blockage in the block or a thermostat problem. I propose redoing the test with the thermostat removed with the bypass blocked and report back.

[henry.blanchette]

Ok, thank you both, that is a lot to think about.

What is the best way to try to bleed the system? is an air lock a real possibility?

Neil,
Yes, it seems that there is not any issue with the raw water side.
No i do not know how the bypass system works, but it looks like that will be my next thing to learn. I will try that test. However, I will say that at one point i ran the engine with the top off the thermostat housing and no thermostat to see if i saw any fluid movement and I did not, I have no idea what that tells me.

I appreciate all the info on upgrades, but I am actually trying to sell the boat, so I'm really just looking to get it running. that being said if any A4 enthusiasts want a really cheap sabre 28 with a hot engine, I'm your guy!

[TimBSmith]

Quick clarification...

Best with your progress and sale...

Not suggesting upgrades just sources for understanding the system you have installed and trouble shooting insights therefrom. Either way godspeed with fix and sale.

[ndutton]

However, I will say that at one point i ran the engine with the top off the thermostat housing and no thermostat to see if i saw any fluid movement and I did not

Well there's a new bit of important information. Without flow you've got nuthin'. Solve the flow first. Either the pump is not pumping or it's not getting any coolant to pump.

edit:
I don't remember reading it but do you have the factory original late model thermostat in the housing on the head or is it an early model Dole or Indigo aftermarket thermostat?

[henry.blanchette]

the lack of flow was why I was wondering if an airlock is a real possibility or if I just did something wrong in attempting to refill coolant and if there is a good way to bleed the system.

I am not sure about the thermostat, but I will take a hard look on friday when I go back out there. I haven't paid much attention yet to the thermostats because I never touched it so I figured the problem would be more likely to lie in something I disturbed