Overheating after Impeller Replacement

ed_hall1

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Joined
Jul 29, 2002
Messages
17
Background Info:
  • 2001 Cobalt 206
  • Engine #: 4012046270
  • Volvo Penta DP, 5.0GIPEFS
  • 118.5 hours on engine
Worked performed:
  • Installed impeller kit part #: 21951348 (included glycerin lubrication pack and new ?O? ring)
  • Replaced thermostat part #: 3856961
What happened:
  • Started boat with out-drive hose attachment.
  • Water did not appear to be fully flowing into the engine.(I?ve noticed in the past that sometime the ears on the out-drive appears to be sucked tight to the drive when the engine is running. This did not happen)
  • Brought boat to local lake and launched to test again under different conditions.
  • Started engine and revved slightly to prime impeller.
  • After a few minutes boat overheated and engine automatically shut down when the engine temperature approached 200 degrees.
  • Allowed engine to cool and tried again. Same results.
  • Re-loaded boat on the trailer and headed home.
What I?ve done so far:
  • Risers checked for blockage (none found ? see picture)
  • Used garden hose to spray water from impeller inlet hose through to the out-drive inlet port without any flow restriction or blockage.
  • Used garden hose to spray water from impeller outlet hose into the engine and out the stern drive exhaust without any restriction or blockage (Engine cold and thermostat most likely in the closed position)
  • Re-inspected impeller (see picture)
  • With the impeller installed in the housing (same as in the picture) , I used my the palm of my hand to seal off the impeller reservoir opening and blew air into the inlet hose opening. Air flowed with little restriction in both directions. Is this correct? I would think that an impeller pump when not spinning would not allow water or air to pass (otherwise all the water in the engine could drain out of the boat when it was taken out of the lake).
Other questions:
  1. Does the impeller need priming? I would think with the hose attachment and pressure at the drive that water would be available to the impeller.
  2. Does the boat have an additional water pump in the engine?
  3. Does the Volvo Duo-Prop out-drive have an impeller?
I was told ?NO? to both #2 & #3 above. Now I am rethinking.

All help would be appreciated.
 

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Lou C

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Nov 10, 2002
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11,802
I've never had a Volvo but I can tell you there is no impeller in a Volvo drive and your engine has a circulation pump on the front of the engine, this circulates water through the block and heads just like an automotive water pump. This does not have anything to do with your problem though. The reason why some Volvos have trouble priming on the water hose is if you think about it, the water must travel up from the water intakes in the outdrive, then through the transom mount and in the hose that connects to the impeller housing on the front of the engine. That is at least a foot of elevation and 3-4 feet forward. By comparison, an outboard has the impeller on the top of the lower unit, it can easily prime and push the water up to the power head. Similarly a Merc Alpha drive has the impeller in the same place as an outboard. So when trying to run a Volvo or even an Bravo engine on the water muffs, you have to make sure that the muffs really fit tightly and water makes up to the impeller housing, or else it will burn up. One thing, I know from other threads on Volvos, that the hoses on the impeller housing have to be installed a certain way and if you mix them up, it will not pump. Did you disconnect both hoses, and get them back on the same way? If not sure about this, that's what I would check first. Because, you also tried the boat in the water and because of static water pressure, the water would pass into the outdrive water intakes, and then fill the hose that goes to the impeller housing. The engine should have been able to suck in water easily with the boat in the water. Your exhaust riser looks fine.
 

bruceb58

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Mar 5, 2006
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Did you remove the hoses from the pump when replacing the impeller? If so, did you put them on in their original positions?

EDIT: I see Lou asked this question already.
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
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47,306
Check the raw water inlet casting on the outdrive as well as making sure the hoses are connected correctly
 

ed_hall1

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Jul 29, 2002
Messages
17
No Title

I did remove the hoses from both the impeller housing and thermostat housing when replacing. I will verify both tonight. I did find a picture of the flow for the impeller (see attached) but does anyone have a picture to verify for the thermostat housing?

I had no issues with overheating prior to the impeller change, but two years ago my impeller had disintegrated and I was afraid pieces might have partially clogged my risers. Both looked fine on inspection. I ordered new riser gaskets today and hopefully can re-test this weekend. I also ordered a new thermostat. This one I will test on the stove top for operation (another potential issue I want to eliminate).

Thanks for all the insights.
 

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dypcdiver

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The lower hose goes directly to the thermostat housing. My money is on the hoses being the wrong way round.
 

billkoller

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Mar 13, 2017
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Run to your hardware store, buy 1"ID clear tubing and put it in place of the hose that goes from water pump to thermostat housing. This will allow you to see if you are pumping water or pumping air to the system. If pumping water (no large bubbles) your issue is past the pump. If pumping air your issue is at the pump or your water supply.
 

mikeneal

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Jan 28, 2004
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710
If the impeller came apart pieces tend to collect in the power steering cooler .
 

BRICH1260

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Make sure you do not have two O rings on the pump housing. This will cause pump to suck air and quit pumping.
 

ed_hall1

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Jul 29, 2002
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I reinstalled the impeller and associated housing last night. Only one "O" ring was installed on the housing and the hoses were banded together in the proper order (so it was impossible even for me to screw up unless I cut the band - which I didn't). I received the thermostat yesterday and will test, verify proper position and install tonight. Still waiting on the riser gaskets. UPS tracker says Monday. I'm hoping for Saturday. I would love to be on the lake this weekend.

I have not looked for or checked the power steering cooler for impeller pieces. Another task on my list for tonight. I may also try the clear hose test to verify prime and water flow to the thermostat housing (with the coil wire pulled to prevent starting).

Lots of great ideas and support from everyone here!!! I'll keep you posted.

Thanks again.
 

mikeneal

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Man, you are right, the cooler is before the pump. Why have I always heard impeller pieces collect in cooler. Are merceusiers plumbed differently? Anyhow, OP please disregard my silly idea to look in the cooler.
Highly unlikely impeller pieces would end up there since it is on the suction side of the pump.
 

bruceb58

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Man, you are right, the cooler is before the pump. Why have I always heard impeller pieces collect in cooler. Are merceusiers plumbed differently? Anyhow, OP please disregard my silly idea to look in the cooler.
In Merc Alphas and OMC, that will happen because the impeller is in the drive.
 

jimmbo

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When I replaced my impeller, I found many pieces jamming up the inlet and outlet holes of the pump.
 

billkoller

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Mar 13, 2017
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Here is another possibility, this happened to me this year already. The seal on the pickup tube on the lower half of the drive failed causing exhaust to fill the water cavity of the drive, So totally submerged drive was drying out with exhaust causing me to overheat. Popped off drive replaced seal and boom works great. Might be worth checking.
 

ed_hall1

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Update? I have now replaced the riser gaskets and reinstalled the thermostat. The thermostat tested fine on the stove top and started to open at 160 degrees and was fully open at 165 degrees. I also verified that it was properly installed (only one way to install the thermostat in the housing on this 5.0L Volvo).

Last night I also put plastic packing tape over my out-drive?s water inlets. This allowed me to pull a vacuum at the impeller hose and test for air entering somewhere from the out-drive to the impeller housing (again no issue here). Next, I removed every hose on the engine and tested for any blockage or debris. I also used my air compressor to blow air through every water cavity on the engine. My goal for this weekend is to purchase a Rubbermaid watering trough at Tractor-Supply. They have a 100gallon one that is 24? deep and should do the trick (I want to eliminate the ear-muffs as a possible issue). The last item before a re-test is to replace my impeller housing. I received a new one in the mail yesterday.

A friend of mine suggested that the thermostat that monitors the engine temperature and automatically shuts the engine down when it approaches 200 degrees may be at fault. Another item to consider.

I am starting to get frustrated and running out of items to check. BTW, there is oil in the engine ? LOL.
 

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dennis461

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In the first post, you did not write why you were changing the impeller, was boat overheating?
Did you make or add any material to the RWP gasket?
Check the raw water pump(RWP) cover for flatness, see my picture.
A more difficult test...
A temporary test-repair would be to connect 3/4" PVC pipe to the RWP or cooler input (instead of the outdrive pickup tube).
Run this through the transom, down below boat bottom.
Add a 90 degree elbow below boat bottom to act as a water scoop.
As boat runs through water, the PVC scoops up water and sends it to the RWP.
If boat engine is normal, you've eliminated heat exchanger and exhaust.
 

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bruceb58

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My goal for this weekend is to purchase a Rubbermaid watering trough at Tractor-Supply. They have a 100gallon one that is 24? deep and should do the trick (I want to eliminate the ear-muffs as a possible issue).
You do not want to do that. The water needs to be at the level of the impeller on the front of the engine and there is no way you are getting it to that level with a trough.

With the engine on muffs and running, pull the hoses one at a time that go from the thermostat housing to the exhaust manifold and see what type of water flow you are getting. The outlets of the thermostat housing can get corroded and limit water flow.

You are running the water to your muffs at full water pressure right?
 
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