HELP! 8.1 Gi-G Persistent Overheating Problem

[Jack D]

Reposting this with additional information hoping for additional ideas: My apologies for the long post but wanted to indicate that lots has been done to try and solve the problem.

I have a Volvo Penta 8.1Gi-G with a 290DP leg in my boat. Engine is 2006 vintage with about 300 total hours whereas the leg is 1994 vintage with about 1300 hours. Engine was installed in 2012 with a reported 25 hours on it. Per records received when I purchased last year, a cooling system valued at approx $1200 was added at time of installation which suggests that the engine was removed from a boat without the cooling system as I?m unaware that the 8.1 Gi-G were ever supplied with only raw water cooling. Adding to this theory, the part?s list for the engine installation makes no mention of a raw water cooling pump being added or the changes that would have been necessary for the serpentine belt changes ? unless the $1200 would have been sufficient for heat exchanger, hoses, complete raw water pump with bracket, and belt changes which would suggest the original engine may have been operated in fresh water with only raw water cooling??

Engine overheats (210 - 215F) when under medium load (3100 rpm) despite a VP mechanic just recently replacing exhaust manifolds, risers and complete raw water pump. As well, heat exchanger cleaned and thermostat changed, After the maintenance, on the first ocean water run, engine temp cycled quickly (1 minute) from 175 F to 210F back to 175 (again when under medium load. Engine temp stayed down at around 180F when at idle. This rapid cycling of temperature had not been experienced before.

After shutting engine off for a few hours to do some fishing, on start up the engine temp then operated differently - rising to 210F and staying there when under similar load for trip back to marina. Since I've owned the boat (8 months) I have never been able to keep antifreeze in the expansion tank although it is not clear where it goes. I add antifreeze to the expansion tank and after running for a couple of hours, with engine still hot, there is no level showing in the tank and no indication in the bilge where the antifreeze has gone, Oil looks good so it is not getting in there.
Mechanic pressure tested the closed cooling system (from the expansion tank filler) and indicated it was OK. Pressure test was done cold so with a closed thermostat.
I will next check out the raw water suction tube and top housing on the leg but I have the following specific queries hopefully forum members can help address:

1. Does checking the cooling system integrity from the expansion tank fully check the system or does the closed cold thermostat foul this test up?
2. One thought I had was whether I have the required amount of antifreeze in the engine or am only slowly getting there with what I am adding to the expansion tank. Is there a procedure to check engine antifreeze level as I don?t believe I?ve come across a pressure cap like you would find on a car radiator?
3. I am thinking that if the antifreeze is boiling off from high engine temp, then when I check the expansion tank with engine still hot I should see a full tank and not an empty one. Any concerns with this thinking?
4. Where can the antifreeze go and what can be checked/corrected if not through a head gasket and into the oil sump? I've only once observed a bit of green in the bilge which could have easily been some sloppiness from the last expansion tank filling.
5. Since a new cooling system was added at time of engine installation, is there anything I should check to confirm that the cooling system was installed correctly? ? particularly if the engine was converted from raw water cooling? The Volvo Penta mechanic who worked on the boat last week indicated that it appears to be a normal factory installed system with heat exchanger and expansion tank in the expected positions.
6. Since the engine became available with only 25 hours on it, and without a external cooling system, I am a bit suspicious that the engine may have had the overheating problem since new and was wondering whether this would suggest other avenues to explore. I have asked VP Canada if they have any information on my engine serial number but they don?t have any record.
7. Any and all suggestions on how to systematically check everything related to cooling problems and put them to be so I can relax and enjoy my boating?

Thanks for any help you can provide.

 

[alldodge]

Sorry to hear of your troubles, but if your gauge is correct and the engine was reaching 210F several times, I would suspect there is a blown head gasket. The the gasket does have a leak the antifreeze could be going right out the exhaust.

Does checking the cooling system integrity from the expansion tank fully check the system or does the closed cold thermostat foul this test up?

Checking the system the way it was done is correct. The thermostat while not open, pressure comes in from all areas and is pressurized behind the thermostat. It is the first law of hydraulics.

One thought I had was whether I have the required amount of antifreeze in the engine or am only slowly getting there with what I am adding to the expansion tank. Is there a procedure to check engine antifreeze level as I don?t believe I?ve come across a pressure cap like you would find on a car radiator?

Don't know for sure but as many times as it has been topped off I would thing it was full. Your mechanic should know how to bleed the air out of the motor, its not that hard to do

I am thinking that if the antifreeze is boiling off from high engine temp, then when I check the expansion tank with engine still hot I should see a full tank and not an empty one. Any concerns with this thinking?
Where can the antifreeze go and what can be checked/corrected if not through a head gasket and into the oil sump? I've only once observed a bit of green in the bilge which could have easily been some sloppiness from the last expansion tank filling.

It would not boil off that fast, my first guess is the head gasket. Need to check the plugs, if it is getting into the combustion chamber it will show up on the plugs. Does the previous engine as well as this engine use a serpentine belt? The reason for asking, is some (not all) serpentine belt motors require a reverse rotation circulating water pump (the one on front of the engine).

Since a new cooling system was added at time of engine installation, is there anything I should check to confirm that the cooling system was installed correctly? ? particularly if the engine was converted from raw water cooling? The Volvo Penta mechanic who worked on the boat last week indicated that it appears to be a normal factory installed system with heat exchanger and expansion tank in the expected positions.
Since the engine became available with only 25 hours on it, and without a external cooling system, I am a bit suspicious that the engine may have had the overheating problem since new and was wondering whether this would suggest other avenues to explore. I have asked VP Canada if they have any information on my engine serial number but they don?t have any record.
Any and all suggestions on how to systematically check everything related to cooling problems and put them to be so I can relax and enjoy my boating?

Have any pics of the install?

 

[Jack D]

Plugs were changed last week along with the other work and the old ones didn't look too bad. Mechanic didn't think they indicated any particular problems but checking compression/head gasket integrity makes total sense.

Original motor was a VP 454 (1994 vintage) and I suspect it didn't use a serpentine belt but in any case, the raw water pump was installed at the time of the changeout in 2012. I will however check the manual for the 8.1 to ascertain the belt is threaded the right way around the raw water pulley.

Although it only lasted an hour or so, any thoughts what would make the engine temp cycle rapidly from 175 F to 210-215F and then back to 175? One minute max to see it swing through this complete cycle and I've never encountered anything similar. Perhaps either slugs of cooling sea water or slugs of antifreeze due to low level?? I don't think a faulty thermostat would do this, especially then change behaviour to constant overheat.

No pics of the installation but I can get one later in the week.

Thanks for your comments and they give me a couple of things to check.

 

[alldodge]

It's not that the belt is threaded right, the water pump on a V-belt motor rotates counter clockwise which is the same as the crankshaft. On a serpentine motor, the belt wraps around the pump in the opposite direction causing it to rotate clockwise. There is no issue with this but you cannot use a V-belt pump on a serpentine belt motor because it will not pump water thru the motor.


Here is the closed cooling designed for your motor

 

[Mytmarty]

I have a 70hp when running full throtle i have an alarm coming on that also starts taking the engine to an idle position. Once i idle the engine for just a minute or two i can run half speed until same thing happens again...i think it my be a heat sensor problem.......suggestions?

 

[alldodge]

I have a 70hp when running full throtle i have an alarm coming on that also starts taking the engine to an idle position. Once i idle the engine for just a minute or two i can run half speed until same thing happens again...i think it my be a heat sensor problem.......suggestions?

Howdy Mytmarty, everyone is welcome on the forum but you should not hijack another persons thread. This is the Volvo Penta section, you should start your own thread in the outboard section of which ever model of motor you have. If you would please do that and there should be some folks along to help you

 

[Jack D]

I checked the serpentine belt and it is as per the diagram and since the raw water pump is new, I've pretty much dismissed it being a raw water pump problem. Not sure how one checks on where the antifreeze is being lost - presumably through the out through the exhaust somehow.

I have a mechanic lined up with temp gun to do a sea trial and the perhaps may suggest next steps but otherwise I am still looking for any and all suggestions.

 

[alldodge]

Sounds good, but just a note about the water pump. All water pumps move water by the means of vanes inside. The angle of the vanes for a pump which is designed to rotate clockwise is a complete opposite to the same pump put on the same motor design to rotate counter clockwise. If the wrong pump was put on the engine by mistake it would still bolt up, it would just have a real hard time trying to move any water being rotated backwards from its designed.

Not saying this has happened, just a note to think about

 

[Jack D]

The raw water pump was supplied by a Volvo Penta dealer and they referred to the model and serial number of my engine when selecting the correct pump. It was subsequently installed by a VP mechanic and he removed the old one before installing the new and I have to assume he did at least a cursory side by side comparison. Hence, although not ruling out a screw up, it would seem to be very unlikely. Temperature gun on the raw water hoses to and from the heat exchanger will presumably provide some idea on whether I am looking at a raw water circulation problem or a closed loop circ problem. Leaving the problem of losing antifreeze still to be resolved.

 

[dypcdiver]

AllDodge is talking about the engine circulating pump not the raw water pump.

 

[Jack D]

OK, gotcha, thanks. From diagram, the raw water pump appears to be crankshaft mounted whereas the engine circ pump is belt driven. Serpentine belt wraps around the circ pump per the diagram so it's turning the correct way, but it still leaves the possibility of the wrong pump being installed - which would suggest a factory screw up since to my knowledge, and based on low engine hours (300), it has never been changed.
Unfortunately, I don't have contact with the previous owner or the firm who installed the engine so I can't determine whether this overheating problem is something new during my ownership or whether it has been with the engine since installation. Sea testing with a Volvo penta mechanic tomorrow and perhaps that will shed some light on the problem and where the coolant is disappearing to.