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Coolant blockage
https://www.ausmini.com/forums/viewtopic.php?f=2&t=58395		 Page 1 of 1
Author:  harry33 [ Sun Nov 01, 2009 11:49 am ]
Post subject:  Coolant blockage
Hi all,

No coolant comes out of the plug at the back of the engine when I take it off.. I've stuck some wire in there to try to clean it out, and I think there might be a very very small trickle of coolant getting through now (or possibly it's just the water I sprayed down there in an attempt to loosen the dirt), but I would have thought it should be pouring out..

Also there's definitely coolant in the head (I took the temp sensor off and it was flowing out pretty fast..)

The only reason I can think of that would explain the lack of coolant coming out of the hole at the back of the engine is a blockage somewhere.. Does this seem reasonable? If so, what are some things I can do to confirm and fix it?

Also my temperature gauge never moves off a point below cold.. I know the gauge works (when I touch the wire on the temperature sensor to somewhere on the fuse box it slowly goes up to hot), so is it likely that the sensor is broken? I've only ever run the engine for about 5 minutes at most though, so I thought maybe it just never gets hot enough.. how long should it take for the gauge to read anything above cold?

Any help would be greatly appreciated..

Cheers,
Harry
Author:  EST-071 [ Sun Nov 01, 2009 12:03 pm ]
Post subject:  Re: Coolant blockage
harry33 wrote:
Hi all,

No coolant comes out of the plug at the back of the engine when I take it off..

This is common

Also my temperature gauge never moves off a point below cold.. I know the gauge works (when I touch the wire on the temperature sensor to somewhere on the fuse box it slowly goes up to hot)

Try putting the sender wire to earth not power and see what the gauge does



Cheers Pete
Author:  drmini in aust [ Sun Nov 01, 2009 12:06 pm ]
Post subject: 
Apart from very early motors that had a brass tap on there, most others had a brass plug which never got taken out since new.
The back of the water jacket there fills up with rust flakes, casting sand etc and it's a bugger to clean out.
However it won't usually affect the motor, there is very little coolant circulation needed in that spot for cooling to be normal.

Often you can clear it with a twist drill and a pair of pliers... :wink:

If rebuilding the motor though it's worth getting it cleared properly while motor is apart. A chemical clean will do it (but is expensive now).
Author:  harry33 [ Sun Nov 01, 2009 12:20 pm ]
Post subject: 
The gauge goes to hot when I put the sender wire to earth. What does this mean?

So should I just not worry about the lack of coolant at the plug for now (I will hopefully get around to rebuilding the engine sometime.. but not yet)?
Author:  drmini in aust [ Sun Nov 01, 2009 12:38 pm ]
Post subject: 
If the gauge goes to H when you ground the wire, that is normal.

Don't worry about that block drain plug for now. Whether water comes out or not doesn't matter. It will not affect engine temp. :wink:
Author:  EST-071 [ Sun Nov 01, 2009 12:46 pm ]
Post subject: 
harry33 wrote:
The gauge goes to hot when I put the sender wire to earth. What does this mean?

That means that the gauge is working correctly, if you think the engine is running hot get a kitchen thermometer and put it in the radiator and see what it reads.
If it reads 80 deg+ I would replace the sender unit.
Cheers Pete
Author:  harry33 [ Sun Nov 01, 2009 8:04 pm ]
Post subject: 
By the way, thanks for the help guys - it's much appreciated.

I had a play with a multimeter and the temp sender.. The voltage across the sender was jumping around pretty wildly between about 1V and 6V, even while the engine was off.. Is this supposed to happen?

Harry
Author:  EST-071 [ Sun Nov 01, 2009 9:02 pm ]
Post subject: 
Should be no voltage at the sender as it is the earth side.
The gauge gets power from the voltage regulator and the sender causes resistance.
Cheers Pete
Author:  harry33 [ Sun Nov 01, 2009 9:15 pm ]
Post subject: 
Sorry - I was talking about the voltage between the nut on the sender (which I assume is earth) and the wire (when the wire is attached to the sender).
Author:  drmini in aust [ Sun Nov 01, 2009 9:52 pm ]
Post subject: 
The gauge and sender are powered by a +10V supply. This is `regulated' by 1950s technology (a glorified bi-metal strip). With the sender taken off the head, there is voltage on that line. A digital voltmeter may read a bit funny though as the regulated output is pretty choppy.
Author:  sgc [ Sun Nov 01, 2009 10:08 pm ]
Post subject: 
drmini in aust wrote:
A digital voltmeter may read a bit funny though as the regulated output is pretty choppy.


That's an understatement :shock:

The one I took off my car a month or two ago was more like a voltage randomiser than a regulator. Even in AC mode the multimeter couldn't get a lock on the voltage output.. I would have been interested to see what the waveform looked like on an oscilloscope...
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