3.0 VP Thermostat

[new2boatz]

Thanks to help from all the great people here at iBoats, I finally got my boat in the water this afternoon for a shakedown cruise. Had a couple issues to start with, but once she warmed up, it was like a brand new engine just as a rebuild should. I only pushed her to about 3500 RPM today and she ran like a top........ Until we went to head back in.


Had stopped in a cove, engine off, for roughly an hour or so, long enough for the engine to cool most of the way back to cold. Got ready to head back to the ramp. Cranked her up, and she fired good. We start easing in, and after it got up to around 140 or so I went ahead and gave it the throttle up to the 3500 RPM I said I ran it at. Out of nowhere, my temp gauge skyrockets after cruising for little to no time. Immediately shut her down, and when I did, it dieseled for a few seconds, and finally shut off. This concerned me a little with it already being hot (gauge read 200+, but gauges lie sometimes too). Would not crank again until it cooled off. I have pulled the water pump, it's good. Took plugs out one at a time and spun her over, no water in cylinders. Therefore, no water in oil. This is where it gets tricky. I had an epiphany and checked the thermostat, rusty as all get out. This was previously a saltwater boat/engine, and I have no clue why I did not think to look at the thermostat before even running it. Took some work to even get it out to test. Dropped it in boiling water, and pulled it out, and sure enough it was opening.

Could it have been stuck, and by my prying and prodding, I "unstuck" it? Any other suggestions as to why the sudden overheat when it was running fine the rest of the day? For those who aren't keeping score in my saga, this is a 3.0 GSPHUB fresh rebuild.

 

[aerobat]

Re: 3.0 VP Thermostat

even with a stucked tstat the gauge schould not "skyrocket" but the engine overheat more "slowly" . of course just put a new tstat in and look. have you checked both pumps? the raw water and recirculating pump ? and of course the impeller ?

look also for the belt tension of your raw water pump to ckeck if its loose or not.

finally. are you sure you can exclude a gauge or sensor error and the engine was overheated for real ?

nevertheless, try to avoid in every case a severe overheating on this freshly rebuild engine !

 

[Don S]

Re: 3.0 VP Thermostat

You could have picked up a plastic bag over the water intakes on the drive. Once you shut the engine off the bag fell off and is now looking for another boat to plug up.

 

[new2boatz]

Re: 3.0 VP Thermostat

even with a stucked tstat the gauge schould not "skyrocket" but the engine overheat more "slowly" . of course just put a new tstat in and look. have you checked both pumps? the raw water and recirculating pump ? and of course the impeller ?

look also for the belt tension of your raw water pump to ckeck if its loose or not.

finally. are you sure you can exclude a gauge or sensor error and the engine was overheated for real ?

nevertheless, try to avoid in every case a severe overheating on this freshly rebuild engine !

The way I understood it, I only have one pump. Am I wrong here? I have a Volvo Raw Water Pump, Part # 3857794. You might be thinking of a Merc unit, that has a pump in the drive and a circulating pump on the engine. We were under the impression this pump did all the work. Belt tension is good. Engine had a good bit of heat radiating from it, so I know it was hot, but not sure if it was quite as hot as the gauge claimed.

You could have picked up a plastic bag over the water intakes on the drive. Once you shut the engine off the bag fell off and is now looking for another boat to plug up.

Don, this was my first thought as well, that the intakes were stopped up. While we were waiting on it to cool, I trimmed up, got out, and felt the drive and found nothing, and saw nothing in the water nearby. I didn't run it very long after it cooled and cranked, but the temperature was jumping pretty quickly again. I didn't let it go over 175 that time, I shut it down before I ever got going real good, and just sat and waited on a tow. Maybe you could shed some light on the issue of the pumps also?

 

[Maclin]

Re: 3.0 VP Thermostat

The way I understood it, I only have one pump. Am I wrong here? I have a Volvo Raw Water Pump, Part # 3857794. You might be thinking of a Merc unit, that has a pump in the drive and a circulating pump on the engine. We were under the impression this pump did all the work.

Yours has both.

 

[new2boatz]

Re: 3.0 VP Thermostat

Yours has both.

Not that I doubt you at all, cause I do see both pumps here: http://www.volvopentastore.com/Exha...on_id.311236566--store_id.366--view_id.778198

But where does this other circulating pump mount? And what belt fits around it to turn it? I was honestly assuming that the manual steering model had both, and mine had just the one, but obviously I'm wrong.

 

[Don S]

Re: 3.0 VP Thermostat

This is a copy and paste from the service manual. it explains the cooling system and how it works.


Description

Water is supplied to the engine by means of an impeller type pump {supply pump). The water
supply pump is mounted on the engine. Water supplied to the engine is circulated in the engine
by means of a centrifugal type pump (circulating pump).

The supply pump used on all models is a self priming impeller type pump, mounted on the
engine and belt driven. During low speed opera* tion the impeller functions as a positive displace*
ment pump. At higher speeds it functions as a combination centrifugal and positive displace*
ment pump.

The shape of the housing and liner cause an eccentric action of the impeller blades
during engine operation. During periods of high speed operation, the resistance of the water
on its way through the pump is sufficient to prevent the ends of the impeller blades from
making contact and following the inside perimeter of the pump housing. The blades merely flex
in toward the center of the impeller to perform as a combina* tion centrifugal and positive
displacement pump.

All Models: The circulating pump is mounted on
the front of the cylinder block. It has a pulley bolted to the pump shaft hub at its
forward end.
This in turn is driven by means of a belt from the crankshaft pulley. The pump shaft and bearing
assembly is pressed in the water pump housing. The bearing is permanently lubricated during
manufacture and sealed to prevent loss of lubri* cant and entry of dirt. The pump is sealed
against coolant leakage by a non-adjustable seal assem* bly pressed into the pump cover.

Cooling water for the engine is picked up at the water intakes on both sides of the lower
gear* case. Water is pulled upward thru the lower gearcase until it enters a water tube that
transfers it to the upper gear housing.

Water is pulled through the upper gear housing water passage where it meets a nipple and hose
attached to the pivot housing. Water is routed through the transom mount assembly to a tube
that's mounted on the inside of the gimbal hous* ing. From this tube the water is drawn through a
supply hose that's connected to the inside nipple of the supply pump. Water exits the
outside nipple of the supply pump under pressure and carried through a hose to the inlet
nipple of the thermostat housing.

All Models: The water is now carried downward through the thermostat housing where it enters the
flexible hose which attaches to the inlet pipe ofthe circulating pump. This inlet pipe is a part
of the pump cover and feeds the coolant into a low pressure area located at the axis of the
impeller. Vanes on the rotating impeller cause the coolant to be thrown outward and into the
cylinder block.

The cooling water flows rearward through the water jacket which surrounds each cylinder and
extends below the lower limit of piston ring travel. After flowing the full length of the
cylinder bjock, the water is forced upward through two passages and into the cylinder head(s).
The wa* ter now flows forward in the cylinder head(s) to cool the combustion chamber areas.

At the forward end of the cylinder head(s), the water enters the thermostat housing. If the water
within the block is sufficiently warmed up, the thermostat will be open and a portion of the
water will be pumped upward past the thermo* stat. The remainder will be returned via the
fh xible hose to the water pump for recirculation within the powerhead. The water which was
pumped upward past the thermostat will enter the hose(s) connected to the thermostat housing
outlet(s) and travel to the manifold(s).

At this point the water flows rearward through the manifold passages and into the
high-rise elbow. All of the water that enters the high-rise elbow is mixed with the exhaust gases
prior to entering the exhaust pipe(s) and hose(s). This mixture of exhaust gases and water then
enters the exhaust passa 1es of the gimbal housing, pivot housing and vertical drive where
it is dis*charged under water.

In the event the engine cooling water is cold, as in first starting up, the thermostat will be
closed and will not allow any of the water to pass through for eventual discharge
overboard. In* stead, the water will be carried via the flexible hose back to the circulating
pump for recircula* tion within the block. While the water within the block is recirculating,
the supply pump is pump* ing water to the block.

Since this water is not able to enter the cylinder block, it is necessary to provide a method of
discharge. This is provided by the bypass pas*sage within the thermostat housing. If this were
not provided, the resulting water pressure would be enough to force the thermostat off its
seat, resulting in a greatly increased warm-up period.

 

[new2boatz]

Re: 3.0 VP Thermostat

This is a copy and paste from the service manual. it explains the cooling system and how it works.


Description

Water is supplied to the engine by means of an impeller type pump {supply pump). The water
supply pump is mounted on the engine. Water supplied to the engine is circulated in the engine
by means of a centrifugal type pump (circulating pump).

The supply pump used on all models is a self priming impeller type pump, mounted on the
engine and belt driven. During low speed opera* tion the impeller functions as a positive displace*
ment pump. At higher speeds it functions as a combination centrifugal and positive displace*
ment pump.

The shape of the housing and liner cause an eccentric action of the impeller blades
during engine operation. During periods of high speed operation, the resistance of the water
on its way through the pump is sufficient to prevent the ends of the impeller blades from
making contact and following the inside perimeter of the pump housing. The blades merely flex
in toward the center of the impeller to perform as a combina* tion centrifugal and positive
displacement pump.

All Models: The circulating pump is mounted on
the front of the cylinder block. It has a pulley bolted to the pump shaft hub at its
forward end.
This in turn is driven by means of a belt from the crankshaft pulley. The pump shaft and bearing
assembly is pressed in the water pump housing. The bearing is permanently lubricated during
manufacture and sealed to prevent loss of lubri* cant and entry of dirt. The pump is sealed
against coolant leakage by a non-adjustable seal assem* bly pressed into the pump cover.

Cooling water for the engine is picked up at the water intakes on both sides of the lower
gear* case. Water is pulled upward thru the lower gearcase until it enters a water tube that
transfers it to the upper gear housing.

Water is pulled through the upper gear housing water passage where it meets a nipple and hose
attached to the pivot housing. Water is routed through the transom mount assembly to a tube
that's mounted on the inside of the gimbal hous* ing. From this tube the water is drawn through a
supply hose that's connected to the inside nipple of the supply pump. Water exits the
outside nipple of the supply pump under pressure and carried through a hose to the inlet
nipple of the thermostat housing.

All Models: The water is now carried downward through the thermostat housing where it enters the
flexible hose which attaches to the inlet pipe ofthe circulating pump. This inlet pipe is a part
of the pump cover and feeds the coolant into a low pressure area located at the axis of the
impeller. Vanes on the rotating impeller cause the coolant to be thrown outward and into the
cylinder block.

The cooling water flows rearward through the water jacket which surrounds each cylinder and
extends below the lower limit of piston ring travel. After flowing the full length of the
cylinder bjock, the water is forced upward through two passages and into the cylinder head(s).
The wa* ter now flows forward in the cylinder head(s) to cool the combustion chamber areas.

At the forward end of the cylinder head(s), the water enters the thermostat housing. If the water
within the block is sufficiently warmed up, the thermostat will be open and a portion of the
water will be pumped upward past the thermo* stat. The remainder will be returned via the
fh xible hose to the water pump for recirculation within the powerhead. The water which was
pumped upward past the thermostat will enter the hose(s) connected to the thermostat housing
outlet(s) and travel to the manifold(s).

At this point the water flows rearward through the manifold passages and into the
high-rise elbow. All of the water that enters the high-rise elbow is mixed with the exhaust gases
prior to entering the exhaust pipe(s) and hose(s). This mixture of exhaust gases and water then
enters the exhaust passa 1es of the gimbal housing, pivot housing and vertical drive where
it is dis*charged under water.

In the event the engine cooling water is cold, as in first starting up, the thermostat will be
closed and will not allow any of the water to pass through for eventual discharge
overboard. In* stead, the water will be carried via the flexible hose back to the circulating
pump for recircula* tion within the block. While the water within the block is recirculating,
the supply pump is pump* ing water to the block.

Since this water is not able to enter the cylinder block, it is necessary to provide a method of
discharge. This is provided by the bypass pas*sage within the thermostat housing. If this were
not provided, the resulting water pressure would be enough to force the thermostat off its
seat, resulting in a greatly increased warm-up period.

So, from what I just read, that three groove pulley, which I called an "idler" pulley, is actually a circulating water pump? I want to make sure I fully understand before I head over to the cabin to check things out as I have no cell service and no internet access there to ask questions once I get there.

 

[Don S]

Re: 3.0 VP Thermostat

Download this manual http://www.4shared.com/office/YhKe25kC/HU_early_NC_Engine_Manual_7788.html? section 9 covers the cooling system.

 

[aerobat]

Re: 3.0 VP Thermostat

The way I understood it, I only have one pump. Am I wrong here? I have a Volvo Raw Water Pump, Part # 3857794. You might be thinking of a Merc unit, that has a pump in the drive and a circulating pump on the engine. We were under the impression this pump did all the work. Belt tension is good. Engine had a good bit of heat radiating from it, so I know it was hot, but not sure if it was quite as hot as the gauge claimed.

like other say you have for very sure TWO pumps. the one incorporates the impeller and is belt driven on the engine periphery ( raw water) and the other is engine mounted below the tstat housing ( circulating) . and yes, we are talking volvo not mercruiser. the volvo ( sx drive ) has the impeller raw water pump belt driven inside the engine compartment , not in the drive !

the heat radiation in the engine compartment has nothing to do with coolant overheating , but neverertheless run the engine blower to suck the heated air out and fresh air in or you may run into other problem when the engine sucks very hot air for combustion.

 

[new2boatz]

Re: 3.0 VP Thermostat

Okay, so update here. As I said, I was completely unaware that I had two pumps, but I now see that I absolutely do. I had been calling that pulley the "idler" pulley, way off base. Now, with that said, previously, I had a small noise coming from this pulley when revving the engine. Took all the belts off, spun the pulley, and sure enough there it was. So I start to think, "okay, bad pump." Pull the pulley off, and the pump spins but doesn't make much noise, at least not like with the pulley. Went ahead and pulled the pump anyway, since I have a spare gasket left over from kit. I can't understand what's going on here. If this pump was bad, what would a tell-tale sign be? Squealing, or what? Seeing how this is basically just like a car's water pump, I started thinking. Your car's pump starts leaking when bad. No leaks, so is this one okay? Well, sorta......

Upon inspection in the house in good daylight, I noticed something very strange. Again, this boat was previously with someone who didn't take care of it, and when he trashed it, he dumped it on his parents. When I got inside with the pump, it looked like it had been welded!!! I was pissed. New pump has been ordered, but what else could cause my overheat? Forgot to mention this earlier, but the engine definitely was hot, as it was tight and would not turn over until it cooled, so I think I can rule out a bad sending unit/gauge, but I don't know.

 

[new2boatz]

Re: 3.0 VP Thermostat

I guess I should ask this also, to anyone who may know, does the 3.0 use a 160 or 143 thermostat? I went down to NAPA today, and they looked in their book to see what they could order, and I have until tomorrow afternoon to correct them and make sure I get the right one in here on Wednesday. I see I can order Sierra part # 18-3558 through them, which says it replaces 3853799 and also says 160, but when looking in NAPA's parts book, it looked identical to a 143 thermostat in there. Just want to make sure so I don't have to waste even more time.

 

[aerobat]

Re: 3.0 VP Thermostat

hey !

first i have to say that it sounds very bad that the engine was so hot it went tight until cooled down , especially if its fresh rebuild with cylinders honed and still in the break in process. but you cannot change this anymore. hopefully there is no further damage.

when it comes to the raw water pump . since you did not knew you have one i guess you never looked for the impeller, right ? it may be as simple as a failed impeller inside this pump and not the the pump itself bad. when it is watertight ans spins you might ordered a new pump for nothing.

the obvious sign of a failed impeller or raw water pump failure is water not pumped through the engine and consequently an engine overheat.

the tstat should be a 160, 143 was afaik the earlier version. buy a 160 tstat.

who rebuilded this engine ? it sounds strange that they rebuild the engine using a rusted old tstat and maybe never changing the impeller .

i would recommend always to start with the easy things. check the impeller, check the belt of the pump if its correct and tight and does not start to slide over the pulley at high rpm,s . in every case make sure water is pumped through the engine.

good luck !

edit : after reading carefully you post you was aware of the raw water imppler pump but not aware of the circulating pump and you ordered a new circulating pump, right ?

 

[new2boatz]

Re: 3.0 VP Thermostat

hey !

first i have to say that it sounds very bad that the engine was so hot it went tight until cooled down , especially if its fresh rebuild with cylinders honed and still in the break in process. but you cannot change this anymore. hopefully there is no further damage.

when it comes to the raw water pump . since you did not knew you have one i guess you never looked for the impeller, right ? it may be as simple as a failed impeller inside this pump and not the the pump itself bad. when it is watertight ans spins you might ordered a new pump for nothing.

the obvious sign of a failed impeller or raw water pump failure is water not pumped through the engine and consequently an engine overheat.

the tstat should be a 160, 143 was afaik the earlier version. buy a 160 tstat.

who rebuilded this engine ? it sounds strange that they rebuild the engine using a rusted old tstat and maybe never changing the impeller .

i would recommend always to start with the easy things. check the impeller, check the belt of the pump if its correct and tight and does not start to slide over the pulley at high rpm,s . in every case make sure water is pumped through the engine.

good luck !

edit : after reading carefully you post you was aware of the raw water imppler pump but not aware of the circulating pump and you ordered a new circulating pump, right ?

Yes, a new circulating pump. I knew about the raw water pump, and *that* pump is brand spankin new, all $300 worth. I rebuilt the engine, and the thermostat just slipped my mind. I was so happy that it cranked once I got it all back together that it just completely went over my head. At any rate, I will head up to NAPA and make sure I get the correct thermostat. I *think* I might be okay, but I don't really know at this point. One thing we do know is that the raw water pump IS pumping water. Buddy of mine talked to someone and they told him we needed to pull the coil plug, disconnect water pump outlet hose, and turn her over and make sure we were pumping water, which we were.

Is there anywhere I should check for some kind of blockage or rusting or anything that would have caused this? I am unsure of my next step beyond getting a new pump and thermostat and gaskets.

 

[aerobat]

Re: 3.0 VP Thermostat

when you verified the raw water pump is pumping your impeller is ok- when its all brand new i see no need to even check and investigate the impeller further. so install the new tstat and the new circulating pump and your overheating will surely go away. i assume you replaced or at least carefully checked the exhaust manifold?

i have a 160 tstat on my 3.0 GS and it runs about 165deg regardless of load. you should read similar values after repair.

 

[new2boatz]

Re: 3.0 VP Thermostat

Everything is supposed to be in by Friday, so I guess its the waiting game now. One thing I still have running in my mind.... Is there anything else.... No matter how trivial it may seem.... to check out before running this bad boy again??? I really don't wanna ruin this engine with only 3.4 hours on it. A blind squirrel finds a nut every once in a while and I think this one found his this past weekend, just want to make sure I've covered all my bases before running this motor again.

 

[aerobat]

Re: 3.0 VP Thermostat

beyond looking carefully on the temps and oil pressures while underway not much. after installing the pump and the housing of course start the engine and look if all it watertight.

when the fresh rebuild engine was as hot that it seized until cool down you either already damaged/ruined it or no further things will happen when it does not overheat again. you could check the compression or just run and look.