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| Overheating at low speed and at high rpms. https://www.smwebhead.com/phpBB3/viewtopic.php?f=11&t=14256 |
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| Author: | su2skelsey [ Mon Jul 13, 2015 1:36 pm ] |
| Post subject: | Overheating at low speed and at high rpms. |
Greetings -- It seems every year I have some type of overheating problem. This year it is something new. I have a 2004 268 Vista, 5.7Gi-EF motor. At idle, I can sit in my slip for 30 ir 40 minutes and the thermostat will come up to temperature (174). When I pull out of the slip and go at the "no wake speed" the temperature starts to climb toward 200 degrees. If I bump the speed up to 6mph + the temperature starts to drop down to 174. When I get up on plane and hit 3600 rpms the temperature starts to climb again to 200. If I drop it back to 3400 rpms the temperature drops back to 174 and runs fine. I have replaced the thermostat at the beginning of the year and when I started to have this problem I replaced the impeller. I am going to go down this week and backwash all the hoses just to see if there is a blockage somewhere. I might have picked up sand or weeds, because I was running fine earlier in the year. I am also, going to use the heat gun on it while I am underway, to see if I can locate a blockage. I just want to know if anyone had this kind of issue, overheating at low and high rpms. I boat in the Upper Chesapeake Bay. So it is brackish water. Thanks in advance. |
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| Author: | su2skelsey [ Mon Jul 13, 2015 1:56 pm ] |
| Post subject: | Re: Overheating at low speed and at high rpms. |
I was just reading another post about replacing an impeller and never saw and o-ring or replaced an o-ring when I replaced the impeller. Does anyone know there is an o-ring to replace in the water pump of the 5.7 Gi-EF engine? I am going to look though the schematic and see if there is one. I've replaced the impellor three time on the boat since I have had it and have never seen an o-ring. Maybe this is the issue. |
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| Author: | afw200 [ Mon Jul 13, 2015 2:10 pm ] |
| Post subject: | Re: Overheating at low speed and at high rpms. |
O-Ring and Sealing Ring... https://www.marinepartseurope.com/en/vo ... -5038.aspx
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| Author: | su2skelsey [ Mon Jul 13, 2015 2:23 pm ] |
| Post subject: | Re: Overheating at low speed and at high rpms. |
Thank, I was just looking at the schematic. I guess I better find that o-ring and see if I can find the old one in the water pump. i've been using the boat for 5 years with replacing the 0-ring. that could be my issue. |
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| Author: | fi.na.tine [ Mon Jul 13, 2015 3:31 pm ] |
| Post subject: | Re: Overheating at low speed and at high rpms. |
Might just be me, but I don't think the O-ring is your issue - sounds more like a flow issue. Have you checked your riser temps? thermostat? Blockages in the hose could also be the cause, but boating in brackish water could also be causing some serious corrosion issues. I know there are others here with more experience and mastery of the craft who can either confirm or deny my suspicions. |
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| Author: | rpengr [ Mon Jul 13, 2015 3:38 pm ] |
| Post subject: | Re: Overheating at low speed and at high rpms. |
That O-ring in the water pump seals both the suction and pressure sides of the pump. If one side leaks, it will leak water out. If the other side leaks, it will let air come in, which could mess with your cooling and temp readings. Either way, it is likely to drip water when the engine gets shut down, so if you don't have any drips, then the o-ring is probably fine. I would also check the thermostat housing. From my experience, it should be changed with every other change of the exhaust manifolds and risers. The housing can get rusted passages that reduce cooling flow...especially in the two ports that go out towards the exhaust manifolds. The temperature of your exhaust manifolds would tell you if you are getting enough water total water flow. If they run too hot, you have blockage somewhere (or bad impeller). If the manifolds run cool, but the gauge says hot, then you have a thermostat problem, or a temperature sensor problem. |
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| Author: | su2skelsey [ Mon Jul 13, 2015 4:44 pm ] |
| Post subject: | Re: Overheating at low speed and at high rpms. |
I am taking the boat out and checking the risers, manifolds, thermostat housing with the heat gun, this week. I did replace the temperature senor a couple of years ago, but that's not to say it didn't go bad again. I think I have a blockage somewhere and I am sure the heat gun will give me a good idea where. Thanks. |
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| Author: | LouC [ Mon Jul 13, 2015 7:12 pm ] |
| Post subject: | Re: Overheating at low speed and at high rpms. |
Since you're in salt or brackish water--as noted above clogging in both the exhaust system and the thermostat housing can cause that problem. In addition, if it's moored or slipped in brackish or salt water marine growth inside the outdrive water intakes can also cause hot running. This problem requires splitting the upper and lower drive housings to clean it all out. Get an IR temp gun and take some readings. Mine when all is good: Intake manifold right under the thermo housing: 155* manifolds at idle: 100*; after running on plane 125-130* Also Google "Volvo Penta Overheat Diagnosis" it is a very good guide to cooling system diagnostics... |
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| Author: | su2skelsey [ Tue Jul 14, 2015 11:29 am ] |
| Post subject: | Re: Overheating at low speed and at high rpms. |
Thanks Lou C -- This is a pretty good diag. http://docslide.us/documents/volvo-penta-overheat-diagnosis.html |
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| Author: | su2skelsey [ Thu Jul 16, 2015 11:44 am ] |
| Post subject: | Re: Overheating at low speed and at high rpms. |
So I took the boat out today and used the IR gun. I had all of Lou C's temps. Everything looked good temperature wise. I think the problem is with the temperature sensor. It climbed to around 200 then back down, while the temperature stay consistant throughout the engine. There does not seem to be a blockage in any of the hoses, risers, or manifolds. I also, looks like the thermostat is doing what it is suppose to. I will update after a bit. |
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| Author: | LouC [ Thu Jul 16, 2015 11:50 am ] |
| Post subject: | Re: Overheating at low speed and at high rpms. |
Nice follow up. Remember that these sensors work on variable resistance. Therefore, any corrosion will cause increased resistance and will mess up your gauge readings. So first, I'd: Clean all the terminals on the back of the temp gauge Clean the terminal on the temp sensor, if it looks like it was installed with teflon tape remove it. It may actually be fine. They don't fail too often. |
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