I was watching my temperature gauge on Saturday and it would go slowly back and forth between the, I'd say, 11 o'clock and 1 o'clock position, every 30 seconds or so. Always in the green zone. I'm assuming that's the thermostat opening and closing. Should it do that or just stay steady at one temp? Is this a foreboding sign that needs attention or a good thing?
Thoughts?
Russell
MD7A Temperature Gauge
Moderator: Jim Walsh
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Russell Skinner
- Posts: 17
- Joined: Feb 8th, '05, 17:12
- Location: Cape Dory 30C-Albatross-Deltaville, VA
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Brian D
thermostat
should be just like your car...comes up to temp and stays there.
My guess is that one of the passages is partially blocked coming out of the block and into the exhaust manifold.
I could be the thermostat, but unlikely...thuy are pretty simple and generally fail in the open position so you would never come up to temp.
Good luck.
My guess is that one of the passages is partially blocked coming out of the block and into the exhaust manifold.
I could be the thermostat, but unlikely...thuy are pretty simple and generally fail in the open position so you would never come up to temp.
Good luck.
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John Nebilak
- Posts: 49
- Joined: Feb 7th, '05, 22:21
- Location: CD36 Indigo, Pt. Richmond, CA
MD7A Temp
Russell,
I recently did a valve job on my MD7A and put in a new thermostat and temp sending unit. I noticed the same fluctuations on the temp gauge. Prior to this work my temp gauge read a constant value but very low on the scale, low side of green. I believe I had the wrong sending unit.
I made sure all passages were clear and clean when I reassembled everything and believe that the motion on the gauge is not representative of any abnormality. I have been running my motoer this way for a year now without any problem.
Hope this helps,
John
I recently did a valve job on my MD7A and put in a new thermostat and temp sending unit. I noticed the same fluctuations on the temp gauge. Prior to this work my temp gauge read a constant value but very low on the scale, low side of green. I believe I had the wrong sending unit.
I made sure all passages were clear and clean when I reassembled everything and believe that the motion on the gauge is not representative of any abnormality. I have been running my motoer this way for a year now without any problem.
Hope this helps,
John
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John Nebilak
- Posts: 49
- Joined: Feb 7th, '05, 22:21
- Location: CD36 Indigo, Pt. Richmond, CA
MD7A Temp
Russell,
I recently did a valve job on my MD7A and put in a new thermostat and temp sending unit. I noticed the same fluctuations on the temp gauge. Prior to this work my temp gauge read a constant value but very low on the scale, low side of green. I believe I had the wrong sending unit.
I made sure all passages were clear and clean when I reassembled everything and believe that the motion on the gauge is not representative of any abnormality. I have been running my motoer this way for a year now without any problem.
Hope this helps,
John
I recently did a valve job on my MD7A and put in a new thermostat and temp sending unit. I noticed the same fluctuations on the temp gauge. Prior to this work my temp gauge read a constant value but very low on the scale, low side of green. I believe I had the wrong sending unit.
I made sure all passages were clear and clean when I reassembled everything and believe that the motion on the gauge is not representative of any abnormality. I have been running my motoer this way for a year now without any problem.
Hope this helps,
John
Temp gauge
Over the 20+ years of my md7a when the temp gauge would start to cycle that would mean a reduction in water flow somewhere.
After cleaning heads and passages, and new thermostat it would return to rock steady......at assigned temp......good luck with finding your problem...... Jim
After cleaning heads and passages, and new thermostat it would return to rock steady......at assigned temp......good luck with finding your problem...... Jim
Jim Lewis
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Russell Skinner
- Posts: 17
- Joined: Feb 8th, '05, 17:12
- Location: Cape Dory 30C-Albatross-Deltaville, VA
Thanks-but doing the work?
Is taking off the thermostat and manifold a doable job for a guy like me, who is a C+ (on a good day) mechanic, or should I have someone who knows what they are doing-do it?
Russell-
I just took mine off last week when chasing an exhaust leak. The job is a piece of cake as long as you are 18" tall or less. Its just a matter of removing a few bolts but the access to that side of the MD7A in our CD 30 is horrible. One of the handiest tools for this project is a small mirror.
The good news ( I guess) is that once the manifold was off I was able to shake out a good deal of rusty junk. I have noticed the same temp gauge fluctuations you mention. The engine is raw water cooled and had a substantial amount of junk in the cooling passages. Pressure water and a magnet were the two best tools for cleaning out the passages.
I removed these parts while searching for the cause of a small but persistent exhaust leak. The manifold gasket was in pretty sorry shape and I hope that that was the culprit. The area around the bottom of the manifold where the cooling water enters the thermostat was blackened with exhaust. I sure hope I don't ever have to tackle the head gasket because there sure isn't much room to work in that engine room.
Good luck.
-Mitch
I just took mine off last week when chasing an exhaust leak. The job is a piece of cake as long as you are 18" tall or less. Its just a matter of removing a few bolts but the access to that side of the MD7A in our CD 30 is horrible. One of the handiest tools for this project is a small mirror.
The good news ( I guess) is that once the manifold was off I was able to shake out a good deal of rusty junk. I have noticed the same temp gauge fluctuations you mention. The engine is raw water cooled and had a substantial amount of junk in the cooling passages. Pressure water and a magnet were the two best tools for cleaning out the passages.
I removed these parts while searching for the cause of a small but persistent exhaust leak. The manifold gasket was in pretty sorry shape and I hope that that was the culprit. The area around the bottom of the manifold where the cooling water enters the thermostat was blackened with exhaust. I sure hope I don't ever have to tackle the head gasket because there sure isn't much room to work in that engine room.
Good luck.
-Mitch
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Brian D
very doable
like most things getting it apart is easy...the hard thing is putting it back together.
two things that make the job much easier are super tak (gasket tack from and auto supply store) and some zip ties.
Use the zip ties at the ends of the manifold to hold the bronze intake pipe in the manifold as you reassemble.
there is one very small orifice that in my experience is the usual suspect...use a small philips head to clean it out...this is on the block itself....of course clean the manifold.
it's about a 3-4 hour job...and of course you have to bleed the engine after. you also need to buy a head gasket repair kit...or maybe you can order the manifold gasket separately. I doubt you will be able to reuse it if it's been on there for more than a few hours of run time.
good luck
two things that make the job much easier are super tak (gasket tack from and auto supply store) and some zip ties.
Use the zip ties at the ends of the manifold to hold the bronze intake pipe in the manifold as you reassemble.
there is one very small orifice that in my experience is the usual suspect...use a small philips head to clean it out...this is on the block itself....of course clean the manifold.
it's about a 3-4 hour job...and of course you have to bleed the engine after. you also need to buy a head gasket repair kit...or maybe you can order the manifold gasket separately. I doubt you will be able to reuse it if it's been on there for more than a few hours of run time.
good luck