both Volvo 5.0 osi overheating at idle RPM

[longpoint]

2003 Volvo 5.0 osi engines (2) 720 & hrs over-heating at idle - occurrs in-gear and in neutral - revving engines in neutral and putting boat under way at 1500 RPMs returns temp to normal, 160 or cooler - started with strbd engine and 3 hours later with port engine - recirc pumps changed a year ago - both impellers replaced in response to this problem with matching Volvo impellers - pumps priming, but still over-heats to 200+ at idle - manifolds get hot and then impeller housing gets very hot activating alarms - running small amount of fresh, cool water through neutral salt tanks returns temps to normal - serpentine belts tight and OK, oil looks good - cleaned intakes on drives (OK) and disconnected both hoses at water pumps (one to engine and one to heat exchanger and back-flushed with dock hose and pressure nozzle and water does evacuate through drives with no apparent obstructions noticeable- heat echangers are original and have never been serviced - could they be the culprit? - this is my first experience with them and i'm thinking blockage from zinc corrosion/gunk - boat in the water - don't know what else to chceck - any advice greatly appreciated-
Longpoint

 

[Don S]

Re: both Volvo 5.0 osi overheating at idle RPM

If the impeller housings get hot, the impellers are dead and must be replaced. Were your neutrasalt tanks empty when the overheats started. I have run into a couple of the valves sticking open, and it WILL cause an overheat. Also, if your engines have the flush hoses on the engine, make sure the caps are tight and don't leak. They also will allow air into the system and an overheat.

 

[longpoint]

Re: both Volvo 5.0 osi overheating at idle RPM

yes, the neutra-salt tanks were empty - the cellinoids were malfunctioning so I disconnected them and installed hose couplers until I could install a ball valve in the lines and use them manually - it didn't occur to me that they may cause a pressure leak and cause over-heating - the engines do not have hose flushout caps - and yes, the impeller housings probably went up to 200 degrees, so they did cook then???

 

[Don S]

Re: both Volvo 5.0 osi overheating at idle RPM

yes, the neutra-salt tanks were empty - the cellinoids were malfunctioning so I disconnected them and installed hose couplers until I could install a ball valve in the lines and use them manually -

That NeutraSalt system was a good idea, just a poor solenoid valve caused all the problem. I had one on my boat (NOT an Osi series) and never had a problem. Just leave the solenoid valve installed, and put your small mechanical ball valve between the solenoid and the feed hose to the pump. That way you can shut it off, but you still have the proper amount of restriction to allow the proper amount of Neutra Salt.

 

[longpoint]

Re: both Volvo 5.0 osi overheating at idle RPM

thanks Don - will try first thing in the morning and report back - if the price of ignorance is only 2 new impellers, i'll be lucky - and I knew I should have looked up the spelling for 'solenoid'

 

[longpoint]

Re: both Volvo 5.0 osi overheating at idle RPM

Don, per your suggestions, I reinstalled the ball valves with the solenoids on the neutra-salt lines and it seems to have corrected the over-heating - thank you - today, in talking to the Volvo shop about manifold replacement (5 1/2 years) they suggested that I strongly consider the stainless steel manifolds - price p/engine though goes from 1500 for cast iron to 3k for stainless - do you have an opinion on that - my worry is that when the engines need to be replace, the application won't work- even now, the new engines are coming w/catalytic converters - do you have any idea how many hours the current 03, 5.0 osi mills are good for with good care and conservative rpm use
Hugh W

 

[Don S]

Re: both Volvo 5.0 osi overheating at idle RPM

If you have been using the neutra salt system, I would hope your manifolds and risers are still in very good shape. I pulled mine off after 3 years to have a look, and couldn't tell them from new.
Just clean the gasket surfaces of the manifolds and risers and make sure they are solid shiny metal and equal thickness of the web all around. If that looks good and it's not clogged up, get some new gaskets (oem of course) and put them back on. Depending on how things look, check them yearly or every other year as long as you are still using the Neutra Salt system. The stuff works great, but that little valve was junk.
Pull the risers (drain the manifolds first) and take some pictures. Lets see how they look after 5.5 years.
Few marine engines die from being worn out. Usually it's from abuse, over propped, water in the engine, improper winterization, lack of manitenance etc. Well maintained and operated with some sense and they should give you thousands of hours of use.

 

[longpoint]

Re: both Volvo 5.0 osi overheating at idle RPM

Thanks Don, that's my sense - there's a small amount of corrosion, and I mean small, in the two corners where the risers meet the manifolds - the Volvo guy, who is no slouch, says that after 5 years I'm on borrowed time - i'm religious, probably overly so, about the neutra-salt flush and the engines run and look better than they did when they came off the floor - so being at the threshhold of killing the engines seems like an incongruant assumption - but then I have experience, but not much training - but the thought of these engines only going 2500 hours and the manifolds being rotten now just doesn't seem reasonable - particularly sense the boat stays in the water and the manifolds don't drain and catch air - I don't even run the engines at over 70 percent except for an occasional few seconds - i'll pull the risers asap next week and take a look - thanks for taking the time to write back -
Hugh W

 

[Don S]

Re: both Volvo 5.0 osi overheating at idle RPM

the Volvo guy, who is no slouch, says that after 5 years I'm on borrowed time

Between 5 and 8 years WITHOUT the Neutra Salt is about the limit for manifolds and risers in salt water. That is why Volvo came up with the Neutra Salt system. To prolong the problems. BUT, if you are concerned, check them yearly. or twice a year if you are really paranoid. But don't throw away manifolds and risers that look ok and haven't caused problems. When the passages are partially plugged with rust flakes and corrosion, then it's time to be concerned. I would sure like to see some pictures of when you first pulled the risers off if you have them.
PS: I also have a nice collection of Volvo Penta certificates I have collected over the years to hang on my wall (if I could find them) I just don't get any money for selling parts to people that don't need them anymore.