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-   -   LT-1 still runs cold (http://www.mastercraft.com/teamtalk/showthread.php?t=48552)

Jerseydave 06-18-2012 11:04 AM

LT-1 still runs cold
 
On my '93 LT-1 it still runs at 120 degrees. (river temp is 68) Here's what I've done so far.

-Verified the guage works by touching the wire to ground.....guage pins to full temp.
-Replace sending unit for guage
-Replaced both t-stats....143 on bottom, drilled 160 on top
-Replaced steam tube at rear of engine with brass fittings and hoses. I cannot move the steam tube to the front of engine because of my high mounted alternator.

t-stat mixing housing at front of engine feels cold to the touch even after running 25 minutes.
Engine runs fine, no sign of overheating, no warning light or buzzer, no leaks.

I pulled the 160 t-stat to make sure its not stuck open and it's closed.
I have not checked the lower 143 t-stat to see if it's stuck open. Could that be it?

Table Rocker 06-18-2012 07:18 PM

The only way I can think of that water could be circulating through the engine with the thermostat closed would be with the heater on (if you have a heater). The closed thermostat should keep cool water from entering the engine and it should warm up.

ahhudgins 06-18-2012 07:38 PM

Just throwing this out there. Just because you ground the wire for the sending unit and the meter pegs, it doesn't mean that the gauge is accurate. If it were me, I would check the ACTUAL engine temp at the sending unit with an infrared gauge. If you find that the actual engine temp is 120 degrees, then you know itís a cooling issue. If you find that the actual engine temp is 143 (or 160, I donít know that engine) then you know you have a gauge or wiring issue. A dirty or corroded wire connection could throw the gauge off.

JimN 06-18-2012 07:55 PM

Quote:

Originally Posted by Jerseydave (Post 849927)
On my '93 LT-1 it still runs at 120 degrees. (river temp is 68) Here's what I've done so far.

-Verified the guage works by touching the wire to ground.....guage pins to full temp.
-Replace sending unit for guage
-Replaced both t-stats....143 on bottom, drilled 160 on top
-Replaced steam tube at rear of engine with brass fittings and hoses. I cannot move the steam tube to the front of engine because of my high mounted alternator.

t-stat mixing housing at front of engine feels cold to the touch even after running 25 minutes.
Engine runs fine, no sign of overheating, no warning light or buzzer, no leaks.

I pulled the 160 t-stat to make sure its not stuck open and it's closed.
I have not checked the lower 143 t-stat to see if it's stuck open. Could that be it?

Any chance that one or both of the thermostats is in with the button on the wrong side?

Jerseydave 06-18-2012 08:20 PM

1 Attachment(s)
Quote:

Originally Posted by JimN (Post 850148)
Any chance that one or both of the thermostats is in with the button on the wrong side?

For sure the 160 is in correctly, I'm going to check the 143 to see if it's stuck open. I'm 99.9% sure I put it in right though.
Jim why would the temp sender be located so close to the water source? Seems to me that that area would always be cool since fresh lake water is constantly entering that housing.
I'm going to check it with a temp gun next time out on the water.

Attachment 80371

Table Rocker 06-19-2012 01:16 AM

I don't have a sensor on the mixer of my '96, only on the water pump. You are right, the water in the mixer would always be cooler.

Is that a temp sensor you can see just to the right of the mixer, inside of the elbow hose? That's where mine is.

Jerseydave 06-19-2012 04:53 AM

Quote:

Originally Posted by Table Rocker (Post 850225)
I don't have a sensor on the mixer of my '96, only on the water pump. You are right, the water in the mixer would always be cooler.

Is that a temp sensor you can see just to the right of the mixer, inside of the elbow hose? That's where mine is.

The temp sensor is on the left side of the mixer, near the black hose in pic. (straight down from the words K&N on the spark arrestor)

Table Rocker 06-19-2012 10:55 AM

1 Attachment(s)
What is that the arrow is pointing to? That is about where my temp sensor is, on the water pump. I wonder if you have two.

pram 06-19-2012 01:58 PM

That is strange for sure to have a sensor on the mixer

my sensor is located where the arrow is pointed also

I do have to say though that mine seems to run colder also according to the temp gauge

took forever to warm up on sun when we went out

didn't want to kick out of high idle

Stx221 06-19-2012 05:35 PM

The temp sensor that the arrow points to is for the ECM. There is another sensor somewhere for the gauge, but I don't know where it is located based on memory. As far as I know, the ECM and the gauge do NOT get a reading from the same sensor.

I can find the location of the other temp sensor for you this weekend when I have access to my repair manual. I wonder if the sensor for the gauge is off slightly, but the ECM is seeing the correct temps? Does the boat run well?

For what its worth, mine runs at approx 140 degrees all day every day...


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