Volvo Penta overheating at idle

[TexasFlyer]

Just wanted to say how much I appreciate this forum, I've found some great info on here. I've found similar topics about my problem on here but none that exactly match my situation so I'll start a new thread on it and hope for the best.

I just bought a 2001 Four Winns Horizon 180 with a Volvo Penta 5.0GL/SX and I couldn't be happier with the boat with one exception. I've had it out twice now and have noticed that it runs right at the top end of the acceptable temperature range when at idle. Once the RPM's come up above about 1600, it cools back into the lowest quarter of the temp range (no numbers on the gauge, sorry I can't be more specific).

After talking to a mechanic and researching on this forum, it sounded like an impeller problem so I replaced that after the first time out. The old one didn't look too bad, it might have taken a little bit of a set but the blades were still in decent shape and still pliable. I just had it back on the water and had the same problem, it never completely overheats but comes close enough to make me uncomfortable, I don't want to fry the head gaskets or cause other damage.

My next step is to replace the thermostat (already have the parts) but I'm trying to figure out my next course of action if that doesn't work. Any ideas of what I might be up against or might try next would be greatly appreciated and I'll be sure to post back with updates so anyone else with the same problem will have a good source to refer back to.

 

[Don S]

Re: Volvo Penta overheating at idle

Might want to read this to get some ideas on how to test things.

http://www.4shared.com/file/50572185/e88f1d89/Volvo_Penta_Overheat_Diagnosis.html


And use the refresh button on your computer, before you repost. I will delete your second post.

 

[TexasFlyer]

Re: Volvo Penta overheating at idle

Thanks, Don. That's the second great reference you've given (the first was the Shop Manual for my boat on another post). Sorry about the double post, this forum loads extremely slow on my computer, don't know if it's my system or just because of the high traffic on the site since it's such a good resource.

I'll replace the thermostat (not too hopeful that will fix the problem but you never know) then go step by step through the manual you provided. I'll post back when I know more. If anyone else has had a similar situation, I'm all ears to hear what you found wrong and how you fixed it. Thanks again.

 

[Bondo]

Re: Volvo Penta overheating at idle

Any ideas of what I might be up against or might try next would be greatly appreciated

Ayuh,... I don't do Volvos,.. But....

Is there a chance that the line feeding the impeller pump is Restricted,..??

Is there a chance that an old impeller broke,+ the pieces were left in the system,.. They'd be downstream somewhere from the impeller pump...

 

[TexasFlyer]

Re: Volvo Penta overheating at idle

Bond-o,

Thanks for the reply, I've been trying to think through the problem and you bring up some great points. As far as the line feeding the pump being restricted, I was thinking about that but wouldn't that cause overheating at all RPM's? Or would the increased RPM's increase the suction enough to overcome the blockage until I was back down at idle? Either way, I plan on flushing the intake side of the system as one of my next steps.

You may be onto something with the pieces of an old pump impeller being lodged somewhere down stream in the system. When I replaced the impeller, I noticed that it was a Johnson brand impeller (not OEM) so it's possible that the impeller before the Johnson might have shed pieces that could be causing a blockage. If that's the case, where would be the most likely choke point downstream where those pieces would lodge?

As far as the thermostat, I'm still holding out hope that it might be the culprit. I'm hoping that maybe it's sticking at low RPM (causing the overheat) and opening when the system pressure increases as I increase RPM's past idle. I only know the basics of how the thermostat works so is this wishful thinking or could it be a possibility?

Once again, thank you for the replies. I'll try everything I can do myself, I really don't want to have to swallow my pride and give the boat over to a shop. They're backing up with work as people take their boats out of storage and have them de-winterized. I really don't want to have to give them my boat for weeks right as the weather is getting nice.

 

[TexasFlyer]

Re: Volvo Penta overheating at idle

Here's an update...

Well, I replaced the water impeller and thermostat and I'm still running hot at idle. I back flushed the intake and exhaust systems and seem to be getting good flow so I don't know if there's any problem there. One thing I did notice was some crusty rust-like build up inside the themostat housing, that has me wondering about the condition of the rest of the system, particularly the circulation pump. Any ideas about where to go from here? I didn't mind replacing the impeller or thermostat as those were relatively inexpensive parts, but I can't see dropping $200 for a circulating pump for a maybe. I hate to say it but I may be throwing in the towel and giving it over to the local marine shop, I'm starting to get frustrated. Any ideas out there???

 

[captmello]

Re: Volvo Penta overheating at idle

Salt water? If so may need some exhaust parts.

 

[TexasFlyer]

Re: Volvo Penta overheating at idle

Well, as promised, I wanted to post back with what I found on my overheating issue so that it might benefit the next guy with the same problem. I learned there's a reason for the order that they have you do things in the troubleshooting guides that helpful folks like Don S post. One of the things I skipped was actually checking the temperature of the engine with an infrared thermometer. I bought one on eBay for $35, then ran the engine up to operating temp on the muff. After checking the block, thermostat housing, risers... basically every part of the engine I could think of to scan with the thermometer, the highest temp I found was about 165F. Conclusion: Bad temperature gauge or sender, engine is running nicely right around the rated thermostat temp of 160.

After checking around on other posts, it sounds like Four Winns went with VDO for their instrument clusters in 2001 and they're not highly thought of by other boaters. So the bad news is now I've got to figure out my gauge issue but the good news is the engine isn't overheating. I've read this could be related to a bad ground with the cluster so I'll check on that but if all else fails, I'll try to rig a seperate temp gauge so I can at least have a better idea of the ACTUAL engine temp.

Just wanted to say thanks again to the folks on this forum for their posts, especially Don S for the links to the manuals.