2000 Volvo 5.0 GL running cold

[jluchuk]

I have a 2000 Larson with twin Volvo 5.0 GL engines that I purchased and just put in the water. I boat on an upstate NY finger lake so the water is fairly cold this time of year. One engine runs fine and the temperature is approximate 170 degrees after it warms up. The other engine however will not go above approximately 100 degrees at idle. Once out at a 30 mph cruise it reached 115 degrees. The only difference between the two engines is that the one running cold does have taps that go to the hot water heater and back to the block. I have replaced the thermostat which did not help. When feeling the thermostat housing, hoses, exhaust lines, etc. they are not warm so the engine is not getting hot. Does anyone have any ideas what the problem may be? I can find nothing wrong. I would appreciate any ideas I can get. Thanks. This weekend I plan to use an IR meter to get a more accurate temperature reading and plan to replace the thermostat again and possibly the thermostat housing but I do not have any confidence that will fix it. Only feedback I get from dealers is it has to be the thermostat.
Jerry

 

[Limited-Time]

Re: 2000 Volvo 5.0 GL running cold

You can swap sending units to rule out that possibility, and compare gage readings as well. And welcome aboard.

 

[Don S]

Re: 2000 Volvo 5.0 GL running cold

What's the full model number of your 5.0GL
Is this a raw water cooled engine, or does it have a closed cooling system?

 

[jluchuk]

Re: 2000 Volvo 5.0 GL running cold

Don , thanks for the quick reply and I am glad to be aboard. I have spent hours reading posts on this site and have learned a lot even though I have been in boating a lot of years. Your question on the full model number - everything I have on the engines are 220HP 5.0 GL PEFS - raw water cooling - starboard serial number 4012013084 Product # 3869056 - that is all the numbers I can find but I am not sure one of these is the model number you are looking for.-- I have a new sender I have not installed which I will try this week end to find out if any of my approaches work. It is funny that most mechanics don't expect cold running problems but just overheating - so knowledge is limited. If you think I should try anything else while I am at the boat this weekend please let me know. I will post what I find after I am back from the holiday. Thanks again.
Jerry

 

[fishmen111]

Re: 2000 Volvo 5.0 GL running cold

Where do the hot water heater lines attach to the motor? The motor is cool to the touch, so I am wondering it the water heater lines are bypassing the thermostat? What temperature stat did you put in?

 

[fishmen111]

Re: 2000 Volvo 5.0 GL running cold

Opps...double post.

 

[jluchuk]

Re: 2000 Volvo 5.0 GL running cold

Thermostat is 160 degrees - hot water heater lines - One comes off of the hose between the circulating pump and the thermostat housing (large 2 or 3 inch hose) It is a tee with a 5/8 feed to the hot water heater - the other line is a 5/8 from the hot water heater to the engine block below the spark plug wires.

 

[Don S]

Re: 2000 Volvo 5.0 GL running cold

Did the new thermostat you installed seat firmly up inside the thermostat housing and stay in place with the oring used as a retainer?

 

[jluchuk]

Re: 2000 Volvo 5.0 GL running cold

OK here is an update - FIrst problem is fixed - of course when I got the old thermostat housing off - the new one would not fit. The problem was blocked water lines in the housing - was parts of an old impeller blade which must be why the one I replaced during the winter looked so good - both the 5/8 input and the little internal bypass hole were plugged - you could not see it but you could not pass anything through the holes until they were cleared. Last time I replaced the thermostat I did not look for blockage because I thought blockage would make it overheat - always something new to learn. Fortunately I had a new gasket and the thermostat and o-ring was OK from last week's replacement because the new parts were the wrong ones. Today I found out that there is a "red" and "charcoal" engine for the 5.0GL that are different. The defining information is the "PEFS" on my engine numbers that differentiate the engines. Thanks for all the help you guys gave me this forum is great. In fact I am opening another thread today for my engine throttle and shift controls because they did not work right this weekend as well and I believe have to be replaced. I will look forward to your help on that one as well. Thanks again.
Jerry

 

[rgood44]

Re: 2000 Volvo 5.0 GL running cold

Sorry to reply to such and old post - but I think I have the same problem. My engine is a 2000 4.3GL PEFS. It is running cool. Just a tad over 100 degrees. I tested the thermostat and it opens as 160 degrees on the dot. How can the blocked water lines in the housing cause the engine to run cold?