www.iFourWinns.com

Hey guys I had problems with the engine overheating last time I took it out so I decided to change the impeller check the thermostat and do a complete circulation check to make sure everything was working ok but I can't seem to identify the thermostat to inspect it.

Is it located inside the part where I circled in white? or is it the two other colors?

Could someone identify all 3 parts while were at it? By witch one should I start? Is one more prone to cause problems then the other?

I have a 1997 volvo 7.4 GI/DP it has a Model # 74FGPLKD that I can't find on the volvo site BTW?????

Could someone confirm the the thermostat should open at 170 degrees?



Here is my old impeller installed that has now been replaced. Once I got it out of there it didn't look so bad.



I also had a little surprise when I opened up the gear oil dipstick. There was still pressure in the gearbox 48 hours after we used it so I'm guessing it was only humidity the milked it up and not a major seal leak. There was no water inside the foot and I have seen some pretty worse looking oil so I am hoping new oil will be all it takes.



As always guys thanks for the input

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97 258 vista 7.4 VP/DP......... 2008 GMC Yukon XL Denali


96 sundowner 5.7 vp/sx (SOLD)

everything you have circled are sensors, the thermostat will be where the upper hose meets the block should have 2 bolts that hold on the housing.

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2000 268 Vista "Reely Nauti"
http://www.facebook.com/#!/rivercruiser

The thermostat is held in place in the housing on a 5.7 with an O ring; maybe different on a big block V8. It will probably not be obvious, as there will be a lot of rust there unless it's got closed cooling.

Graham

I was thinking of removing the thermostat and boiling it to see at what temp it would open at. If its inside that housing it will be a heck of a job to get out of there. I wish my infrared thermometer would be here already would make the job easier.

Could those two other sensors be the cause of the problem?

The one in red is not hooked up to anything but the one in blue is.

I wonder witch one is connected to the temp gauge in the dashboard?

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97 258 vista 7.4 VP/DP......... 2008 GMC Yukon XL Denali


96 sundowner 5.7 vp/sx (SOLD)

In your first post you said you had a 7.4 (454 cu in) then in your second one your signature says a 5.7...anyway on most of these the thermostat is very easy to change...2 bolts you remove the housing...turn it over....pry out the rubber o ring and the thermo comes right out. The thermo is rated for 160* F. And if your gear oil is that high I'd check it for water..it's likely that water is being drawn in and rasing the oil level.

7.4 parts pic:


http://www.dougrussell.com/partscatalog ... ,2533,2528

5.7 parts pic:
http://www.dougrussell.com/partscatalog ... ,2863,2504

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88 Four Winns 200 Horizon
4.3 OMC Cobra-4bbl
2002 Walker Bay 10/2012 Suzuki 2.5
2008 Walker Bay 8

1998 Jeep Grand Cherokee 4.0/Selectrac
2007 Jeep Grand Cherokee 5.7 Hemi/Quadradrive II

I do have the 7.4 don't know where 5.7 came from??? Any idea of an easier way to check if it works properly? The oil level on the dip stick was high cause I had it in the up position just before I took the picture.

Both the blue and red thermostats I circled do not show up on the diagram provided in the link?

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97 258 vista 7.4 VP/DP......... 2008 GMC Yukon XL Denali


96 sundowner 5.7 vp/sx (SOLD)

sorry about that I didn't see that the 5.7 was the one you sold...anyway the 2 sensors you circled will be referenced in other sections of the parts catalog depending on which engine system they are part of...the one on the intake will be in the engine or intake/carb section...not sure were the other one will be but you may have to go to Volvo parts...look up your year and engine size and look through all menus till you find it...

if you have an overheating problem...it can be the impeller...thermostat...clogged manifolds/risers...or even parts of an old impeller lodged somewhere...you have to check each item and elimiate them one by one....

_________________
88 Four Winns 200 Horizon
4.3 OMC Cobra-4bbl
2002 Walker Bay 10/2012 Suzuki 2.5
2008 Walker Bay 8

1998 Jeep Grand Cherokee 4.0/Selectrac
2007 Jeep Grand Cherokee 5.7 Hemi/Quadradrive II

There was a lot of barnacle like stuff on the lower but I mostly took care of it with the pressure washer. I verified the flow of water from the hoses that lead to the water pump with my garden hose and everything flowed well.

As for the risers can those just be taken off to clean without too much problems? I'm not a mechanic and wouldn't want to get myself in any trouble.

Al tho I did thing changing the impeller was a hard job before I ended up with the water pump in my hands....LOL!!!! Now I know to never pay 300$ to get one of those changed.

Getting back to my thermostat, I hope I can just take off the housing without having to take the top off the the engine to access the thermostat?

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97 258 vista 7.4 VP/DP......... 2008 GMC Yukon XL Denali


96 sundowner 5.7 vp/sx (SOLD)

When I do these I put them back together with OMC gasket sealer as per the manual and I have never had a problem getting them off...I even changed a thermo on the water once with no issues...
In fact today I had to remove the carb on my old '88 for a rebuild and I took off the thermo housing to get better access to the fuel line and its two bolts...(9/16ths I think...) and you might have to rap the housing with a plastic hammer to get it to break free but it's very easy as long as the bolts come out...I put the OMC gasket sealer on the bolt threads and again they come right out...this is a 22 year old boat...used in salt at least 1/2 of that...

risers...well it's the same deal as long as the bolts come out...


barnacles you might want to take a real close look in the water intake holes because I get them growing in there after 6 months in salt water...I take the drive off for winter...in the spring I remove the impeller housing (Cobra drive has the impeller in the upper gear housing) and I break up the shells with a small screwdriver...then I hook up the muffs and water hose and blast em out...with the impeller housing out of the way they do come out...you would not have to do this on a Volvo obviously...but look in those holes closely....

_________________
88 Four Winns 200 Horizon
4.3 OMC Cobra-4bbl
2002 Walker Bay 10/2012 Suzuki 2.5
2008 Walker Bay 8

1998 Jeep Grand Cherokee 4.0/Selectrac
2007 Jeep Grand Cherokee 5.7 Hemi/Quadradrive II

I finally got around to testing the new water pump impeller with the garden hose water adapter. took a while for the temperature to rise but it kept going until it reached 150/160 and pretty much leveled off there. So I guess we could say the thermostat is working. Will take her out for a water test tomorrow and post back.

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97 258 vista 7.4 VP/DP......... 2008 GMC Yukon XL Denali


96 sundowner 5.7 vp/sx (SOLD)

I might be a little late here, but just changed the thermostat on my 7.4L Merc., but I am assuming Volvo uses the same GM casting? My therostat is located on very front top of the engine. Two bolts to remove it and a few hoses that attach to it. Other than that pretty simple swap out. From what I can tell what you have circled in white is the Thermostat housing.

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1998 Baja Boss 252 7.4L MPI Bravo 1 (SOLD)
2007 FW H200SS 5.0GXI (Sold)
2004 Chevy Silverado 2500 Crew 6.0L (tow vehicle)
1991 FW 170 Freedom 4.3L (SOLD)

Well was a heck of a nice day on the water. The temperature did not go any higher than 230. I still would like it to not go any higher than 180 but I was told the temps I was getting were normal?????

any thoughts?

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97 258 vista 7.4 VP/DP......... 2008 GMC Yukon XL Denali


96 sundowner 5.7 vp/sx (SOLD)

WHO are you asking for information?? They don't know what they are taking about and are giving BAD advice...
a raw water cooled sterndrive with a 160* thermstat should run at just that +-10*....my 22 year old OMC 4.3 with the 160 stat runs at 160 pretty much all the time...(salt water engine at that)
180 even is a bit too hot for raw water cooling.. but it would be fine with closed cooling....keep in mind raw water cooling is not a presurized system like a closed cooling system with a 15 psi cap that raises the boiling point of coolant to 265*F...at 180*F on the gauge...you can get localized boiling in hotter parts of the engine...230*F is BAD....get this thing to a mechanic if you want to have it be reliable for the season...but as I said...the basics are raw water intake (not clogged) impeller (not worn) thermo (not sticking...opening at right temp) risers/manifolds (not rusted/clogged with rust) drive belt (not loose) circulating pump on front of engine (not leaking)....that's about all the things that can cause an overheat...

one last thing...if you had a previous impeller failure...and it lost blades...those could have clogged other parts of the cooling system...but on a Volvo with the engine mounted pump I'd expect to find those in the thermo housing...

if your engine did not overheat on the water hose on land...but overheats on the water...it's possilble that even if the impeller is good you might have a clog in the risers...check the temp of them....if they are too hot to put your hands on them after running on plane for a while then that's a possibility...but you should NOT keep running the boat if it gets to 230...that's risking a blown head gasket....

_________________
88 Four Winns 200 Horizon
4.3 OMC Cobra-4bbl
2002 Walker Bay 10/2012 Suzuki 2.5
2008 Walker Bay 8

1998 Jeep Grand Cherokee 4.0/Selectrac
2007 Jeep Grand Cherokee 5.7 Hemi/Quadradrive II

I am planning on changing the thermostat just the same.......Just in case... but there has been some improvement since last Thursday when the engine went into shutdown cause of overheat well over 240.

Still looking at taking apart the risers..if its not that complicated I will take em off clean and put back together.

will I need gaskets for the risers and water pump or liquid gaskets are good?

_________________
97 258 vista 7.4 VP/DP......... 2008 GMC Yukon XL Denali


96 sundowner 5.7 vp/sx (SOLD)

[/quote]I am planning on changing the thermostat just the same.......Just in case... but there has been some improvement since last Thursday when the engine went into shutdown cause of overheat well over 240.

Still looking at taking apart the risers..if its not that complicated I will take em off clean and put back together.

will I need gaskets for the risers and water pump or liquid gaskets are good?[/quote]


Yep you need gaskets and make sure you get the correct Volvo ones because if you use the wrong ones it can cause water to get sucked back into the engine (NOT GOOD)....probably a good idea to replace the bolts too if they are really rusted. Is this a freshwater or salt water boat?

_________________
88 Four Winns 200 Horizon
4.3 OMC Cobra-4bbl
2002 Walker Bay 10/2012 Suzuki 2.5
2008 Walker Bay 8

1998 Jeep Grand Cherokee 4.0/Selectrac
2007 Jeep Grand Cherokee 5.7 Hemi/Quadradrive II