Engine Temperature

[ghebbns]

Hi all,

Brought Sabbatica back to her home port today - about a 2 hour motor.  In the past, she has always been at a steady 165 degrees.  I noticed during our trip that the temperature would inch up to around 170 and then quickly drop to 160 and repeat.  I was cruising at 2200 rpm.  When I reached our cove, I had to slow down as there was an abundance of lobster traps making for a challenging entrance. The temperature gauge went up to around 200.  It would drop down but more slowly.

The only thing I did to the engine this year was change the impeller.  There is a steady stream of water coming out the exhaust.

Any thoughts on what the issue is and what else I should be checking?

Thanks,

Greg

[mark_53]

Did you clean your sea strainer recently? If not you may consider doing so. If that doesn't help, remove the sea strainer and see if the tru hull is blocked.

[ghebbns]

Thanks, I have done that.  As I said, there is plenty of water kicking out the exhaust so I don't think that is the problem.

[Ken Juul]

check the electrical connections on the engine and gauge.  May be some corrosion.

[mark_53]

Thanks, I have done that.  As I said, there is plenty of water kicking out the exhaust so I don't think that is the problem.

Check your thermostat or pump on the coolant side.  Check coolant level also.

[ghebbns]

How do I check the coolant level?  I don't have an expansion tank.

Thanks

[Indian Falls]

I ran a bit low on antifreeze and overheated instantly.  One day it was fine the next the temp alarm was going off.  Took off the radiator cap added some fluid. All better.  Seems very sensitive and goes along with the temp swing you saw going into a lower rpm.

[Stu Jackson]

How do I check the coolant level?  I don't have an expansion tank.

Whether you have an expansion tank or not, you NEED to regularly check the coolant level at the top of the exhaust manifold (i.e., radiator cap).

[ghebbns]

I think this is my problem - my coolant level was very low. 

In looking at my engine, I do not have an expansion tank but the opening by the cap is there and open - probably why I am low.  I will install a tank.  Just wondering where people have it installed on their c34?  I believe it has to be higher than the engine, correct?

Thanks

[Stu Jackson]

I will install a tank.  Just wondering where people have it installed on their c34?

Read the May 2000 Tech Notes Online.  A description of how, what and where is right there for you.

[KWKloeber]

Whether you have an expansion tank or not, you NEED to regularly check the coolant level at the top of the exhaust manifold (i.e., radiator cap).

Greg,

If you ck the coolant level regularly as Stu says, and you find that the level consistently drops for no apparent reason (which leads to the overheating) you may need a new Hx. 

If a pinhole develops in the Hx tubes (between the sea water and coolant side), the pressure (12-15 psi) in the block pushes coolant out the exhaust when the engine comes up to operating temp.  You lose some coolant, and the pressure rises even more quickly next time and lose more coolant -- until you eventually overheat. 

If you install a recovery tank and it  regularly gets sucked down, you may have a pinhole in the Hx.  Even if you do, the tank may not suck back into the block when the engine cools -- instead the vacuum created may be relieved by the pinhole in the Hx.  The only good way to tell, is to pressure test the closed coolant system.

Ken

[ghebbns]

Just a follow up to this situation.  My coolant level was very low.  I filled it and installed an expansion tank.  I had some other work to do so I just started the engine and let it run at the dock.

I had it at idle to begin with and then increased it to around 2k rpm.  After around 45 minutes, it was still just a touch over 120 degrees.  I decided to take it for a spin to see what happens when it is under load.  Our cove is just under a mile long.  It was foggy out on the bay so I just went to the end of the cove and back.  Motoring at around 2300 rpm, she heated up to around 155 by the end of the cove (maybe 10 minutes of motoring) and was right at 165 by the time I got back to the dock.  The only difference from the past that I noticed is that when I slowed down to turn around (from 2300 to idle), the temperature shot up temporarily (to between 165 and 170).  Once I sped up, she went back down.  Is this normal?  I haven't really paid as close attention to temperature variations in the past (just make sure she doesn't overheat).

Thanks for all the help and suggestions.

[Stu Jackson]

The only difference from the past that I noticed is that when I slowed down to turn around (from 2300 to idle), the temperature shot up temporarily (to between 165 and 170).  Once I sped up, she went back down.  Is this normal?

1.  You seem to be running cool.  What temp thermostat?

2.  Yes, it's "partly" normal, because when the engine is hot and you back off on the throttle the rw pump slows down.

3.  OTOH it could be you need a new rw pump impeller.

[ghebbns]

Thanks Stu.  I am not positive about the thermostat but I believe it is 165.

I just changed the impeller and there is a good flow of water out the exhaust.  My thought is to just keep an eye on this and make sure there is no overheating.  I also did a less scientific test of putting my hand near the engine after I turned it off and it certainly did not seem hotter than usual.

Greg

[Stu Jackson]

It's either 160 or 180, they don't make a 165.  Sounds good, though.