99 Volvo Penta 5.0 GL Heating Issue

[Bhuie]

Guys I have a cooling problem.
New hoses, thermostat, impeller and engine water pump last year and boat has been ran once since all of this started. Couple weeks ago after running first time which ran beautifully it got hot after about 15 minutes. Figured the thermostat got stuck and second time around put her in the water and ran same amount of time and saw the temp drop when she hit 160. Took her out for a longer period and did fine but after 30 minutes or so I noticed overheating like going last 3/4 in the gauge. So by the time we got back she was hot again (as in alarm going off). I replaced the thermostat. Yesterday. Took her out and noticed the thermostat working bit again over time gets hot. So I turn it off about 5 minutes and when I start her back up again she is immediately at 3/4 hot. This happens a few times until I realize hey I’ll start just killing it and restarting it again quickly. So basically the engine after it gets hot and the alarm goes off if I idle, kill the motor and then immediately restart it the temperature goes back down to normal operating for a while. What the heck could this be about?
I will say the fattest hose from the engine house to the thermostat is hotter than the other three smaller hoses.
Thanks,
Brad

 

[alldodge]

Check the intake hose connection. The aluminum fitting can get clogged up

Since it has overheated a couple times, and the fitting is clogged, the impeller may need to be replaced again

 

[Bhuie]

Check the intake hose connection. The aluminum fitting can get clogged up

Since it has overheated a couple times, and the fitting is clogged, the impeller may need to be replaced again

I will check that and report back. Any chance it could be a bad temperature sensor? I thought it strange to be able to cut it off then immediately start it back up and be able to run for a while..

 

[Augoose]

Hose from engine house to thermostat? Do you mean from the water pump to the thermostat? Check out the illustration below to ensure your hoses are running correctly. #9 comes from the lower unit, #23 goes from the water pump to the thermostat, and then #7 and #8 distributes water to the manifolds.
Are your manifolds too hot to leave your hand on the top once the engine is fully heated up? Once the engine is warmed up, if you hold hose #23, can you feel water flowing? I can on mine.

 

[alldodge]

I will check that and report back. Any chance it could be a bad temperature sensor? I thought it strange to be able to cut it off then immediately start it back up and be able to run for a while..

It would be best to verify that it is overheating, but doubt its the gauge. Your motor has a temp sender which sends signals to the gauge for visual reference.

The other is a temp switch the sounds the alarm. The switch and the gauge are not connected together. So the gauge reads its hot, and the switch closes and sounds the alarm when the motor is hot

 

[Bhuie]

Hose from engine house to thermostat? Do you mean from the water pump to the thermostat? Check out the illustration below to ensure your hoses are running correctly. #9 comes from the lower unit, #23 goes from the water pump to the thermostat, and then #7 and #8 distributes water to the manifolds.
Are your manifolds too hot to leave your hand on the top once the engine is fully heated up? Once the engine is warmed up, if you hold hose #23, can you feel water flowing? I can on mine.
View attachment 339569

Thanks for the diagram. 23 is always hotter than 7 and 8. I can put my hand in the manifolds and leave it there. 23 I can leave my hand there for a little while and the metal below the temperature sensor (which is underneath hose seven) in the block is hot to touch. I can leave my fingers there for a few seconds. Shift over a couple inches to the right and the block is cool behind the thermostat housing.

 

[QBhoy]

I’d also check if you have a power steering oil cooler on the suction side of the water pump. Known this to draw air and have a similar result.

 

[Bhuie]

I’d also check if you have a power steering oil cooler on the suction side of the water pump. Known this to draw air and have a similar result.

No power steering

 

[Bhuie]

I’d also check if you have a power steering oil cooler on the suction side of the water pump. Known this to draw air and have a similar result.

I stand corrected there is something cooling the steering. The line that comes in from the foot in the back of the motor goes into a black cylinder and then another hose from there goes to the lower unit. I’m going to start checking for debris there.

 

[Bhuie]

Check the intake hose connection. The aluminum fitting can get clogged up

Since it has overheated a couple times, and the fitting is clogged, the impeller may need to be replaced again

Can you explain to me in a little better detail where this aluminum fitting is that you speak of? I hope it isnt in the foot.

 

[Lou C]

It’s normal that the big hose will be hotter that the other 3 and in fact the two hoses feeding the manifolds will be cool until the thermostat opens allows hot water to leave the block. Then they should warm up although not as hot as the big hose gets.
To verify temps use an IR temp gun take a reading of the intake manifold right under the stat housing that will usually be about 10* lower than the gauge reading. If this reads like 150-160* then the engine is not overheating and it’s a gauge or sending unit/wiring issue.
This being a ‘99 it’s probably an SX drive and on these there is a plastic fitting in the pivot housing that can crack if the boat is not winterized properly and can suck in air when the boat is on plane.
V/P has a document called engine overheat diagnosis it’s a PDF see if you can find it and take a look at the diagnostic procedures they recommend.
PS
I might pull out the stat and test it in a pot of hot water to make sure it opens at 160* which is standard for Volvo stats on these models. I use an old fashioned automotive radiator thermometer to test these before I install one. Never had a bad one but I guess it’s possible.
My more common problems had been the stat sticking open or or not closing all the way due to a flake of rust caught in it and then the engine won’t warm up till it’s on plane. Idle it won’t get over 100-120 when that happens. Rust from inside the engine and intake makes this a chronic problem on raw water cooled I/Os.

 

[Bhuie]

Hose from engine house to thermostat? Do you mean from the water pump to the thermostat? Check out the illustration below to ensure your hoses are running correctly. #9 comes from the lower unit, #23 goes from the water pump to the thermostat, and then #7 and #8 distributes water to the manifolds.
Are your manifolds too hot to leave your hand on the top once the engine is fully heated up? Once the engine is warmed up, if you hold hose #23, can you feel water flowing? I can on mine.
View attachment 339569

OK!!! After further review, what happens if hose 9 attached to 18 (water pump?) is swapped and on the bottom instead of the top? Hose 9 goes to the thermostat. I’ve changed hose 9 to go on the top (swapped the hoses here) where the diagram shows. I’m about to take her out and see what happens.

 

[Augoose]

OK!!! After further review, what happens if hose 9 attached to 18 (water pump?) is swapped and on the bottom instead of the top? Hose 9 goes to the thermostat. I’ve changed hose 9 to go on the top (swapped the hoses here) where the diagram shows. I’m about to take her out and see what happens.

I would expect you wouldn't get cooling water flow. Its a pump; if the hoses are connected backwards you wouldn't be pumping raw water up from the lower unit and into the thermostat.
I would also inspect your impeller now and ensure it wasn't damaged due to a lack of water and overheating.

 

[Bhuie]

OK!!! After further review, what happens if hose 9 attached to 18 (water pump?) is swapped and on the bottom instead of the top? Hose 9 goes to the thermostat. I’ve changed hose 9 to go on the top (swapped the hoses here) where the diagram shows. I’m about to take her out and see what happens.

definitely not the hoses being swapped. Got hot pretty quick but I noticed I couldn’t touch the manifolds like I could before. Also the temperature gauge didn’t get all the way in the Ted like it’s been doing before. Any ideas?

 

[Augoose]

I wonder if your impeller is toast. If you ran the boat for any length of time with the hoses reversed from the schematic, that's likely an issue. I'd check it asap.

 

[Bhuie]

I’m in the boat now. Hoses were not reversed...figured that out quick! Gauge never got passed 3/4 however which I thought strange. Alarm did sound. Hoses stayed squishy when revd. Anyway put them back in place. Could not get it hot sitting in water. After almost 30 minutes of running it is not getting hot at all. I’ve been running it hot and letting it idle but have not turned her off for this period yet. I can run hard and watch the gauge go up between half and 3/4 then at idle come slowly back down. I don’t know what’s happened but I did take a look at that back steering cooler behind the engine where the cooling hose comes in from the foot. All was clean back there. Any thoughts?

 

[alldodge]

Sitting in the water does not put any load on the motor, so its not building much heat even if reved

Need it run it the water to load motor

 

[QBhoy]

I stand corrected there is something cooling the steering. The line that comes in from the foot in the back of the motor goes into a black cylinder and then another hose from there goes to the lower unit. I’m going to start checking for debris there.

Thought there might be. Check it’s not corroded or compromised. It can draw air and lose its prime on the pump.

 

[Bhuie]

Thought there might be. Check it’s not corroded or compromised. It can draw air and lose its prime on the pump.

Ok,
Power steering oil cooler looked clean as a whistle. I did check the hoses on both ends (left side was a *****!). After putting the hoses back right I let her run for 15 minutes and revd engine.
I decided to take her out to try and replicate the heating problem from yesterday. I went that far following same route and never got hot.
Drove around for over an hour driving the **** out of her and never cut her off even at idle.
Never got hot.
I have no idea what the deal was. I’m assuming faulty sensor or junk/debri free. I do know the previous owner the day I drove her for inspection he drove it over an hour and never overheated.
I have an ir temperature thermometer gun that I’ll keep in the boat and check the motor at times. Especially if I see it’s getting hot again.
thank you all for the advice!
Let me know your thoughts on this but I’ll consider it fixed unless it occurs again and my Ir gun actually says it’s hot.

 

[QBhoy]

Ok,
Power steering oil cooler looked clean as a whistle. I did check the hoses on both ends (left side was a *****!). After putting the hoses back right I let her run for 15 minutes and revd engine.
I decided to take her out to try and replicate the heating problem from yesterday. I went that far following same route and never got hot.
Drove around for over an hour driving the **** out of her and never cut her off even at idle.
Never got hot.
I have no idea what the deal was. I’m assuming faulty sensor or junk/debri free. I do know the previous owner the day I drove her for inspection he drove it over an hour and never overheated.
I have an ir temperature thermometer gun that I’ll keep in the boat and check the motor at times. Especially if I see it’s getting hot again.
thank you all for the advice!
Let me know your thoughts on this but I’ll consider it fixed unless it occurs again and my Ir gun actually says it’s hot.

Excellent