Universal 5411 overheating after flush

[Gary_H]

Ok guys thinking that I was being proactive this weekend. I flushed my 5411 (raw water cooling) with a vinegar water solution using a 5 gal bucket and a small pond pump. I let it circulate for 24 hours. I also checked the raw water pump and found a blade missing so I replaced it. Also replaced thermostat.. not new but one I had cleaned.
Problem...now it overheats. Discharge when there was a discharge from the exhaust looked muddy at first. Then I got to were there was very little discharge. Shut her down and let cool change thermostat again...long story short I tried several times and she would go past her running temp each time. Also noticed that the water in the raw water filter was now muddy looking, almost black.
I'm thinking a couple of possibilities right off the bat. That the flushing created a sludge inside the cooling chambers in the block or that the missing impeller blade is stuck somewhere.
My question is can I flush with high pressure water (dock hose) IF I first take out the thermostat, remove the hose from the top of the thermostat that goes to the exhaust T and plug that nipple? That way water will not fill the water lift muffler and back up into the cylinders'.

 

[jibes138]

Gary,
Your post is confusing. The thermostat is part of the engine recirculating cooling system. It works to modulate the temperature at a constant by flowing antifreeze coolant through the engine. The raw water system is a heat transfer system that removes heat from the engine cooling system in a heat exchanger and ejects the hot water overboard. If you are lacking flow out the exhaust it is nothing to do with the thermostat. You have a blockage of some type in the raw water system or the raw water pump is not functioning correctly. If you lost an impeller vane it is probably blocking flow in the heat exchanger. Also pieces of pencil zinc in the heat exchanger build up over time and will eventually block flow as well as build up of salt and minerals from the sea water. Another place to look is the nipple that goes into the exhaust pipe to see if that is blocked. Take the outlet hose off the pump and see if you can blow through it either with a hand pump or your mouth by wrapping your hand around it and blowing through your hand (so you don't get nasty stuff in your mouth. Otherwise remove your raw water hoses make sure they are free and clear and remove the end cap from your heat exchanger to see if there is a clog. Best bet is to remove the heat exchanger and have it cleaned out by a HX shop but that disrupts the engine cooling system and you will need to refill and burp the air out of that system. If you think your thermostat could be bad put it in a pan with water and heat it up to see if it opens before the water boils. You can put a meat thermometer in the pan to see if it opens at the right temperature. Low flow out the exhaust though points to a restriction in the raw water or the impeller. Also make sure you have flow through your through hull. The marine growth in our area is extreme and your raw water inlet might be clogged. I just removed my raw water through hull strainer and replaced with a 3/4 inch mushroom head through hull so I can make sure it stays clean. There is no way to clean out the inside of those strainers and stuff can grow in there. Pull your raw water inlet hose off the strainer and hold it above the water line with the sea cock open, using a funnel pour water into the hose and see if it goes down, this will indicate if you have flow through the strainer and hose but not really if the flow is enough, but will show if there is a total blockage or if the water goes down really slow if it has a bad restriction.

 

[Gary_H]

Jibes my system doesn't have a heat exchanger. I added a picture of my system to my original post.

My system works this way: From the manual:

I]1. Sea water enters through sea water inlet,
2. Through sea water valve when open,
3. Into mixing tee to suction side of pump, located below water line.
4. Out of pump by hose to inlet on side of block,
5. Circulates through block into cylinder head,
6. Leaves head on top front to exhaust manifold,
7. Circulates through manifold to thermostat,
8. Enters thermostat which remains closed during warm up, permitting a small amount of water to
enter exhaust system for cooling and overboard
9. As engine temperature rises the thermostat starts to open, letting hot water enter exhaust line. At
the same time the same amount of cool sea water is drawn in by the pump to replace the discharged
hot water. This is done through the mixing tee which is located below engine (or water line) to
prevent air from entering the system.
10. There may be some fluctuation in engine temperature until engine stabilizes.
11. In areas of cold inlet say 50oF, you may notice some movement from 136oF to 155oF as engine
r.p.m. are changed. This is less noticeable with warmer inlet waters. The reason being that the
colder water causes thermostat to react faster than engine temperature stabilizes

 

[jibes138]

You could have an air lock in the system. Is there a valve on top of the thermostat to let the air out? I understand you have a raw water cooled engine block. On my thermostat housing (M25 engine) there is a valve that you open until antifreeze comes out to let the air out of the system. This is once the thermostat opens to allow flow. Also, do you have an engine heated hot water heater? These can also become air locked preventing full flow of coolant.

 

[Gary_H]

No I don't have valve on top of my thermostat housing the hose from there goes straight into the exhaust riser. I don't have a water heater in my system. My system is pretty simple, only two moving parts, the pump and the thermostat piston. I guess it could have an airlock in the system like you suggest.

 

[Charles Erwin]

Gary

You mention a 'raw water filter' and 'discolored water'. This filter is not shown on your diagram. Can you explain the filter more fully?

Charles

 

[Apex]

Put a set of calipers on the old and new impeller, I found the new 0.005" thinner, and would not flow water well unless I ran the engine (water pump) at higher revs at which time it could overcome the impeller/housing gap.

 

[Gary_H]

This what my thermostat looks like except there is another number 9 on the top that goes to the exhaust riser.

 

[Gary_H]

Gary

You mention a 'raw water filter' and 'discolored water'. This filter is not shown on your diagram. Can you explain the filter more fully?

Charles

Yes on my boat there is a strainer between the raw water inlet valve and the mixing T. Everything else is identical to the picture.

 

[Gary_H]

Put a set of calipers on the old and new impeller, I found the new 0.005" thinner, and would not flow water well unless I ran the engine (water pump) at higher revs at which time it could overcome the impeller/housing gap.

I will do that, I'm also going to order a brand new impeller from Universal Torresen.

 

[Charles Erwin]

Probable the thermostat is permanently stuck in recirculation position thus does not allow water overboard.

Remove thermostat. Pinch closed the recirculation hose - the one between the thermostat housing and sea water intake. Start motor. All water should pass overboard via exhaust. Check thermostat in hot water (150 deg or higher)

Otherwise to fully diagnose:

1. Remove sea water pump outlet hose. Start motor momentarily and check flow during motor on. Reattach if acceptable. If good flow then pump and intake are good.
2. Remove hose between motor to exhaust. Start motor momentarily. Check flow. If good then no restriction in the motor cooling passages.

Charles

 

[Gary_H]

Probable the thermostat is permanently stuck in recirculation position thus does not allow water overboard.

Remove thermostat. Pinch closed the recirculation hose - the one between the thermostat housing and sea water intake. Start motor. All water should pass overboard via exhaust. Check thermostat in hot water (150 deg or higher)

Otherwise to fully diagnose:

1. Remove sea water pump outlet hose. Start motor momentarily and check flow during motor on. Reattach if acceptable. If good flow then pump and intake are good.
2. Remove hose between motor to exhaust. Start motor momentarily. Check flow. If good then no restriction in the motor cooling passages.

Charles

OK I will try that see what happens. Thanks Charles.

 

[Charles Erwin]

Do give us a final report?

 

[Gary_H]

Do give us a final report?

Will do, unfortunately it might be a week or so before I can get back to the boat.

 

[Gary_H]

So I had to take off and go to the boat because some guy named Arthur is coming to town. So I doubled up on all lines and lashed down anything that could catch the wind. but as long as I was there. I decided to power flush the Raw water intake and strainer. do a freshwater flush on the engine again, check the pump output volume, and check the exhaust water injector hose. After which I put everything back together and started her up. She did much better this time although the temp gauge indicated 160 to 165, I made some readings with my laser thermometer on the engine and also the thermostat housing. It was showing around 144 to 150 during the run time. So the question is... which reading do I believe, which is most reliable? the gauge or the laser thermometer? I'm incline to believe the thermometer.
The outer bands of the hurricane were hitting us as I left. I'm hoping she will ride it out as nicely as she did the last two.

 

[Chris Patterson]

Gary, my money is generally on the laser. Providing I have used this tool in the past and have some level of trust in it..

 

[jibes138]

Thermocouples can drift and lose calibration. We used to test them before using them for critical brazing processes to make sure they were accurate. So there could be a large error in your temp gage. That said, my Universal M25 is specified to run at about 160 degrees. It doesn't sound like your temp is in the danger zone but it will run hotter under load compared to idling at the dock. Did you have good coolant flow out the exhaust?

 

[Gary_H]

Thermocouples can drift and lose calibration. We used to test them before using them for critical brazing processes to make sure they were accurate. So there could be a large error in your temp gage. That said, my Universal M25 is specified to run at about 160 degrees. It doesn't sound like your temp is in the danger zone but it will run hotter under load compared to idling at the dock. Did you have good coolant flow out the exhaust?

Yes there was a good flow, Of course mine only flows when the temp reaches 140 and the thermostat opens. When I get back to the boat I will run it under load and see what the range is. The 5411 optimum temperature range according to the manual is 135-155 I know that larger engines that have a heat exchanger can run a lot hotter because they don't have to worry about the salt crystalizing in side the engine passages.