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Engine Overheating.......maybe?
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Author:  AlexJ [ Fri May 08, 2009 9:34 pm ]
Post subject:  Engine Overheating.......maybe?
My temp gauge normally reads about a quarter up or at the first indicator normally. This season, it is operating at the half way marker and sometimes at 3/4 up but steady. I checked the impeller and it is in good shape. I'm thinking that the thermostat might not be opening but a hair. Is that possible? The engine is a '99 and it overheated once before where I had to replace the block but the last 3 seasons, it seamed to be ok at the 1/4 mark or the first indicator. Would it be the thermostat or is it something else?
Author:  moku'ula [ Fri May 08, 2009 10:36 pm ]
Post subject:  Re: Engine Overheating.......maybe?
I have a '99 with the 4.3 GL...

When I bought it the impeller was toast, so I replaced that then had to pull off the t-stat housing to get the pieces of the impeller out of there. While checking out the t-stat I realized it was in pretty bad shape too. Replaced it along with a new o-ring and gasket and life has been good since - knock on wood... Cheap part, easy fix, cooling system seems to be happy...

Jef
Moku'Ula
'99 Horizon 180 LS
Author:  ht32bsx115 [ Fri May 08, 2009 11:11 pm ]
Post subject:  Re: Engine Overheating.......maybe?
AlexJ wrote:
My temp gauge normally reads about a quarter up or at the first indicator normally. This season, it is operating at the half way marker and sometimes at 3/4 up but steady. I checked the impeller and it is in good shape. I'm thinking that the thermostat might not be opening but a hair. Is that possible? The engine is a '99 and it overheated once before where I had to replace the block but the last 3 seasons, it seamed to be ok at the 1/4 mark or the first indicator. Would it be the thermostat or is it something else?


Hi Alex,

Is this a closed cooled or raw cooled engine?

A lot of times an over heat is an indication problem.... You need to verify that your gage is actually registering correctly.

Go to Harbor Freight and pick up a temp gun like the one below for about $30
Image

You can point it directly at your thermostat housing and see if your gage is lying or not.

Then if you can it might be a good idea to replace your "idiot" gage with one that actually reads in degrees instead of 1/4, 1/2, 3/4, red/green etc!

If you're raw cooled it should be around 140-160* If you're closed cooled it can be 160-180 and be ok.


Cheers,


Rick
Author:  AlexJ [ Sat May 09, 2009 7:09 am ]
Post subject:  Re: Engine Overheating.......maybe?
Thanks for the input. It is raw water cooled.
Author:  captkevin [ Sat May 09, 2009 8:20 pm ]
Post subject:  Re: Engine Overheating.......maybe?
How old is the impeller? I'd replace the thermostat & see what that does & go from there.
Author:  AlexJ [ Sun May 10, 2009 8:56 am ]
Post subject:  Re: Engine Overheating.......maybe?
The impeller is a year old. I'm going to replace the thermostat this coming week to see if it makes a difference.
Author:  captkevin [ Sun May 10, 2009 1:49 pm ]
Post subject:  Re: Engine Overheating.......maybe?
When the temp is high try reducing speed to idle - see if it comes back down - if it does replace the impeller - cheap insurance.
Usually you can get several years out of them but if you are having problems don't risk it.
Author:  ht32bsx115 [ Sun May 10, 2009 6:29 pm ]
Post subject:  Re: Engine Overheating.......maybe?
Maybe there's another way to put this......how do you know it's overheating?
Author:  AlexJ [ Sun May 10, 2009 8:14 pm ]
Post subject:  Re: Engine Overheating.......maybe?
I really don't know if it is overheating. I'm just overly cautious since I had to replace the engine a couple of years ago. It isn't normal for me to see the temp. gauge read one thing and at the same level for three years after the engine replacement and now see that it reads another notch higher. I'd rather be safe than sorry.
Author:  ht32bsx115 [ Sun May 10, 2009 8:57 pm ]
Post subject:  Re: Engine Overheating.......maybe?
AlexJ wrote:
I really don't know if it is overheating. I'm just overly cautious since I had to replace the engine a couple of years ago. It isn't normal for me to see the temp. gauge read one thing and at the same level for three years after the engine replacement and now see that it reads another notch higher. I'd rather be safe than sorry.


Ok,

Well, to be "safe", you need to determine if your gage is actually reading correctly instead of randomly replacing parts.

It will really be cheaper in the long run....and you'll actually find the problem!
Author:  robbo3 [ Sun May 10, 2009 10:36 pm ]
Post subject:  Re: Engine Overheating.......maybe?
Mine was running a little warm in the fall and it turned out my impeller had shed a few fins. Even though it had been new in the spring, it was shot, I guess Volvo has had problems with some of their impellers recently.
Author:  dplsys [ Mon May 11, 2009 6:13 am ]
Post subject:  Re: Engine Overheating.......maybe?
Rick's suggestion of the laser temp gun was an excellent one. It will tell you exectly if you have a problem on not and give you a good indication if your gauges are accurate.

On my old Maxum 3000SCR with raw water cooled 4.3L, I went through a fustrating couple of weeks were the alarm bell would trigger near WOT but be fine at lower speeds. The temp gauges showed no problems. My mechanic went for a ride with me ($$$) whipped out the laser gun. He instantly showed the problem was temp. Now I own one. The issue was the raw water pump that time, a quick rebuild did the trick.

On saltwater boats it is also a good idea to shoot risers every once and a while. It will give you an early indication if the water passageways are starting to close up.

Dave
Author:  aguyindallas [ Tue May 12, 2009 9:30 am ]
Post subject:  Re: Engine Overheating.......maybe?
Just as an FYI - my raw water cooled 5.0 typically reads between 160-170 degrees on my gauge.

I am with the above, replace the thermostat. Its cheap and pretty easy. With all the "minerals" and garbage in the water, those things can get clogged and weak and not open properly, or at all.
Author:  AlexJ [ Fri May 15, 2009 8:01 pm ]
Post subject:  Re: Engine Overheating.......maybe?
I checked the temp of the thermostat housing with a laser temp device and found that the area read 146 degrees max. I let the engine idle for 10 mins. and also increased the rpms with the drive disconnected at the throttle control and the temp was steady at 146. I did notice something accidentally. I had the fan on and turned it off and noticed that the engine temp. dropped. I decided to turn it back on and the bilge pump, cabin lights, and nav lights and so on. The temp gauge went into the red but the laser still showed 146 degrees. The question now is what electrically is causing this increase? Can it be the temp sensor on the thermostat housing? All of the other gauges check good and the VDO was tested last year at the four winns repair shop. I saw the testing device, pretty neat. So, any ideas out there?
Author:  dplsys [ Sun May 17, 2009 5:55 pm ]
Post subject:  Re: Engine Overheating.......maybe?
Based on the testing you did your problem is electrical. But where? The temp sending unit works by changing the resistance to ground. So you could use an Amp meter to measure this change in resistance.

1) Remove the wire off the sending unit
2) Take your trusty Radio Shack digital multimeter with some alligator clips. One end to ground, One end to the end of the sending unit. The shop manual for your engine should have the Ohms range for the sending unit listed. (Anyone have one handy?)
3) Complete the same test and see if the sending unit jumps in value.

If it does, then replace it. If it doesn't:

1) reconnect the wire to the sending unit
2) disconnect the wire to the back of the gauge
3) find a good ground at the dash, or better yet run a wire back to the NEG terminal of the battery. Clip the multimeter to the end of the WIRE and to the battery or ground.
4) repeat the test. If the value jump, then you have a wiring problem in the harness back to the engine.

If it doesn't: Look for a loose wire around the dash. The positive 12V to the guage may loose.
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