over heating Volvo Penta

[regal2460]

Greetings All ? new to the forum, and need some help

I?ve got a 2001 Volvo Penta 5.0GI with a temperature gauge that started reading 190 to 200 F last year. Put a new raw water pump in last year prior to launch and changed it again this year.

1) First thing I did last year was to replace the thermostat ? made no difference.
2) Also replaced the circulating pump ? that?s not the problem.
3) I?ve also checked the riser/manifolds with a laser indicator/infrared temp gauge ? riser and manifold temps are good (130 F).
4) Assumed it was the temp gauge, and replaced it ? no change in temp reading
5) By passed the out drive by feeding fresh water directly into the raw water pump ? no change.

Had a couple of mechanics that suggested that I run the boat without the thermostat and recheck the temp ? I did that for about 20 minutes after which time the engine started to run a little rough. Stopped the engine, and a week later tried to restart. But the engine would not start, turned over very roughly but would not catch. I checked all the spark plugs and they were all wet. My mechanic claimed this was this was a blown head gasket and over the winter ripped the engine down, machined the heads and rebuilt the engine.

Summer 2007 - Yupp, you guessed it, put the boat in the water and the temp gauge is back up to 190 ? 220 F. The mechanic is guessing that there is a exhaust leak getting into cooling sytem that is causing an erratic reading of the temp sensor by introducing bubbles around the sensor. So he put clear hoses on the thermostat housing leading the exhaust manifold. He claimed that if there were no bubbles in the water flowing thru the hose that we could rule out an exhaust leak. The port side hose was practically foam, the starboard side seemed reasonable. By the way ? we were running this test without a thermostat being in. In spite of the initial concern my mechanic had over an exhaust leak, ?don?t worry about it ? just run with out a thermostat?.

Does anyone have any ideas??

 

[Cherishher]

Re: over heating Volvo Penta

Wait a second....doesn't the foam confirm the mech's suspicion that there's an exhaust leak and if so shouldn't this be taken care of? After all, it would confirm that the increased temperature is real, right?

Is this the same mechanic that rebuilt the engine over the winter? If so, shouldn't he correct this under warranty having been the one that rebuilt the engine?

 

[Don S]

Re: over heating Volvo Penta

Did anybody check the temp sender?????
Take your IR Temp gun with you next time, and when the temp gets up to 190?, check right at the base of the temp sender and see what it reads there.
ANY, and I mean ANY air leak in the exhaust system around the sensors is NOT going to be a problem, they can't suck in air, they are on the pressure side of the cooling system and the last thing in the cooling system. All the water has passed the engine to finally get to the exhaust and those alarm sensors.
Did the alarm go off? Did they hook up the diagnostic computer and verify temps with it?
DO NOT run without a thermostat. You get the front of the engine cooled, but not the back.
When the test for air bubbles was done, was the boat in the water or on muffs?

 

[regal2460]

Re: over heating Volvo Penta

Don S - yes, sorry I forgot to mention, we've replace the sender 3 times. Its not a leak around the sender that I'm concerned about. It the potential for a exhaust leak into the cooling system from some other place ...manifolds? And the bubble test was done in the water, not with muffs. No alarms have gone off. and no to the diagnostic computer to verify temps....not sure that I've ever seen any of the mechanics use that around here.


Cherishher - yes- your correct, my feeling exactly

What I was hoping that someone might have some idea where I can check. Unfortunately, I'm not getting a favorable response from the mechanic that I'm using and I'm afraid that if I don't solve this myself, it will never get done.

Oh yahh, I also did not mention that I now have new risers now too.


ideas?

 

[Don S]

Re: over heating Volvo Penta

IF, and I mean IF, you are sucking air into the system and getting bubbles anywere in the system, it has to be coming from somewhere BEFORE the raw water pump. After the outlet side, it's all pressurized to 3+ psi. You can't suck air into a system that is pressureized.
It would really help me if you had the full model number of your engine. Not just the 5.0GI, but the letters after that, or even the SN of the engine.

 

[regal2460]

Re: over heating Volvo Penta

Don S

The model # is 5.0GI PEFS
serial # 401246177

You had suggested that any bubbles had to be coming into the cooling system prior to the raw water pump. But I did try an experiment where I by-passed the entire outdrive by connecting a clear hose (to be sure I did not starve the cooling system for water) directly to the raw water pump and ran fresh water into the system - still over heated.

Also in an earlier part of this discussion you had mentioned that running without a thermostat would cause the back end of the engine to not get sufficiently cooled. I'm not debating the point - but I don't understand why that would happen.

thanks for your time.

 

[Don S]

Re: over heating Volvo Penta

The reason it happens (as I understand it) the opening where the thermostat goes is very large, compared to the opening of an open thermostat. With water flow that fast, it doesn't really have time for heat transfer.

On to your problem, are you ABSOLUTELY positive the thermostat is up inside the housing and held in with an oring, and the spring is pointed down toward the engine?
Also, the EF model engines are 2000, not 2001.
Are you in fresh water or salt water?
Is this engine raw water cooled?
Have you checked the manifolds and risers and the joint between them to be sure they are not plugged or damaged?

 

[Don S]

Re: over heating Volvo Penta

One other thing you might want to do is a leakdown test. Not so much for the valves and rings, but the cooling system. It may be you have a cracked block or head, not just a bad head gasket. But, when you do this do one thing a little different.
On your thermostat housing remove the 2 bypass hoses going directly to the exhaust manifolds. Now, put some clear hose on them and hold them up in the air and fill with water. Now do a cylinder leakdown test on each cylinder and see if there are bubbles in the water or the water level rises. This would indicate there is a leak and which cylinder, but not where the leak actually is. IF it does bubble or the level rises a little bit, you need to pull it apart and inspect the engine.

 

[regal2460]

Re: over heating Volvo Penta

DonS

I'm not sure exactly what a cylinder "leakdown" test is. Could you give me more details.

Thanks Agian

 

[Casmoboy2171]

Re: over heating Volvo Penta

I ran into this problem last year. I tried everything that I read as well as suggested by mechanics. I had the impeller changed prior to all of the issues. My boat would idle and run fine, but it did not take long for it to overheat. I did all of the thermostat removal/ replacement stuff with no luck. Finally, after a few weeks, I went into the engine compartment and started removing hoses on the water intake side. The hoses on mine go from about 2 inches close to the water pump to about 1/2 inch at the thermostat entrance. When I removed the hose, I found pieces of impeller lodged in the hose causing a restriction in the water flow. I removed the pieces, hooked everything back up, started the engine and it never overheated again. Maybe this could be your issue, just a suggestion to check.

 

[regal2460]

Re: over heating Volvo Penta

Thanks Casmoboy - Its worth looking at. I know that I've never had problems with the water pump impeller, but the previous owner might have. I'll check - thanks

 

[njlarry]

Re: over heating Volvo Penta

My '95 5.0 FL raw water cooled is doing the same thing. If the IR temps on the risers, manifolds and thermostat housing are normal would that not mean a fautly sender?

 

[regal2460]

Re: over heating Volvo Penta

njlarry

Thats a possibility - they're cheap enough to swap out. That, unfortunately did not work for me. If your sender replacement doesn't do the trick, you can also try swapping out the temp gauge (that also did not work for me).

 

[njlarry]

Re: over heating Volvo Penta

I have a FourWinns VDO gauge set so I can't change the gauge. I wonder if the problem might be related to the temp sender location and the new thermostat.
I replaced the thermostat this spring, tested both the old and the new. They both opened at the same time but the new closed much quicker as the water cooled. In fact the old thermostat had to almost get back to room temp to close completely. Also the old thermostat had a small notch cut in the metal valve that the new did not. Could is these differences allow the engine to run a little hotter, the temp sender is located in the hotted flow but the IR temp read lower because the riser and thermstat housing is cooler? Has anyone else seen a notch on the valve? It looked factory done.
BTW the IR reads right on when tested at various temps.

 

[masterchef]

Re: over heating Volvo Penta

wow now that sounds like my problem I have a 1964 reniel with a 4cy volvo but don't know much about it and it's overheating took thermostate out and fixed a broken pipe and replace a hose water is flowing all the way in and out of the motor but still overheats I feel for you and if thier is anyone who could help me with my problem I would be gratefull

 

[Don S]

Re: over heating Volvo Penta

Masterchef
Time to start a new thread of your own. Best not to ask your question on a year and a half old thread. In no time your post will be lost and not read by anyone. Besides, your 1964 4cyl. cooling system is nothing like the original posters engine 2001 5.0L V8.