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Old 26-10-2019, 05:59   #1
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Volvo MD17C cooling issue

I've started having an issue with my MD17C. The engine starts, warms up, then goes way into the red zone on the temp gauge. (I don't know how accurate that is or the sending unit) The engine sound changes, then I get what appears to be steam out the exhaust, then the exhaust get loud (like there is no water in it) At some point during the "steaming" the temp gauge drops rapidly into the middle green. Then the water starts coming out the exhaust again, with decreased noise.


I shoudl add this is a raw-water cooled engine - no heat exchanger.


What I've tried:


New thermostat - I thought maybe it was sticking or working at the wrong temp? Did not fix it, actually, the new one seems a bit worse.


Took the thermostat out. Engine stays all the way "cold" as expected, but I don't get steam/noise anymore?


So, what's my issue? 2 bad thermostats?



Is running "full cool" with no thermostat a problem?


Thanks everyone!
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Old 26-10-2019, 07:59   #2
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Re: Volvo MD17C cooling issue

Running on full cool is bad for the engine. It will clog up with soot etc. from the exhaust plus combustion may also be more dirty. Check the regular things, impeller may have lost a chunk that is blocking. Do you have an auxillary water supply for flushing the engine? It may be open sucking in air which could account for the up and down temperature. Water supply thru-hull may be partially blocked. Let us MD17C owners know what you find out please.
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Old 27-10-2019, 16:16   #3
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Re: Volvo MD17C cooling issue

If your thermostat doesn't have a vent hole, you're probably getting an air lock under the thermostat. When the engine fills with water when it's cold the thermostat is closed and usually the air traps the water some distance below the thermostat. As the engine warms, it gets overheated, makes steam. Eventually the steam rises and causes the thermostat to open. Having the vent hole allows some water to pass thru the engine ensuring heated water gets to the thermostat spring. Because the spring that expands/contracts to operate the thermostat is out of the water, it doesn't sense the heat fast enough. (Water transfers heat much better than air).
If the thermostat plate doesn't have a small hole (about 1/16"), drill it. Your thermostat may look different.
ditto: don't run the engine under power cold.
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Old 27-10-2019, 16:40   #4
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Re: Volvo MD17C cooling issue

Long period overheating issues with my MD17D (FW cooled) ....... found a major culprit a month or so ago....

Coverplate on the raw water pump was worn.... ie when you look at it outer part ( where the impeller blades are doing the rotating) it is worn down compared with the centre disc.
This is not a 35 year old cover plate but a 10 year or so old Speedseal.
Machined flush again.... 90% of problem gone but even without a thermostat ( all part of the testing process) still sits on the edge of the red at 1800rpm.... can't run at 2000...

So... I have decided that if there was wear on the cover plate ( running in silty water? Non genuine impellers?) then there is probably also wear on the other side of the impeller... ie in the pump body itself....

So next step , when I am next in Oz, is to buy a complete new Ancor replacement pump....and fit it when next on the boat in March 2020

Watch this space....
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Old 27-10-2019, 17:46   #5
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Volvo MD17C cooling issue

If your where your not able to surface the cover plate back smooth, you can usually flip it over on most pumps until you can surface it.
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Old 27-10-2019, 17:58   #6
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Re: Volvo MD17C cooling issue

If you have a raw water cooled engine & it is being used in salt water & have overheated it you need to do a descale probably.
However seeing you are in Michigan maybe not.
Otherwise what Lepke said
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Old 28-10-2019, 08:24   #7
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Re: Volvo MD17C cooling issue

I just went though this problem on 41 year old MD 17C and had to take the cooling manifold off and clean out all the tunnels and also the intake pipe connection. All were blocked.
Also have had to get a second hand gear box as the friction material on the original is worn out. No one at Volvo Spain or head office would, or could give me the specifications for the material. Spain said buy a new engine!! Had clutch and break expert put in material, but material did not work. Had my first Volvo engine in 1974 when there service was great. Times and their service has changed!!
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Old 28-10-2019, 08:53   #8
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Re: Volvo MD17C cooling issue

I have a bunch of MD17 parts for sale. Heads(populated), heat exchangers, water pumps, and probably some other misc stuff...
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Old 28-10-2019, 09:14   #9
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Re: Volvo MD17C cooling issue

The normal water flow in the raw water cooled MD17 goes from the sea water pump to a "T" fitting on the underside of the exhaust manifold. At the T fitting the water can go two directions:
#1 it can continue on past the T and into the thermostat housing, flowing alongside the closed thermostat and out of the housing to the exhaust mixing elbow. This is the normal flow when the engine is cold and the thermostat is closed. Or,
#2 it can flow into the T and into the exhaust manifold water passages, from there into the cylinder heads, down into the cylinder liner passages, back up into the head and out of the head into additional passages in the exhaust manifold. There it contacts the thermostat and when it gets hot enough it causes the thermostat to open and it flows thru the thermostat and into the thermostat housing and then to the mixing elbow and overboard.

When the thermostat gets hot enough to open, it's motion blocks or partially blocks the flow in path #1 and causes flow to begin in path #2. So the
thermostat regulates the engine temp by causing water to flow in one path or the other, or perhaps a bit in both.

When you start the engine from cold, there is plenty of water flow out the exhaust because the thermostat is closed, causing all of the pumped water to bypass the engine and go out the exhaust. As the engine starts to warm up, the thermostat begins to open, which closes off the the bypass water path in the thermostat housing and that should force water thru the engine path. Evidently this engine flow isn't happening, so the water that's in the engine overheats and steams, probably until it's mostly gone and then nothing comes out the exhaust.

When there is no more water in the engine, the thermostat, (no longer touching water) closes, again allowing water to flow in the bypass and cooling the exhaust.

When you run the engine without the thermostat in place, bypass water flows into the thermostat housing and also into the front end of the exhaust manifold, because there is no longer a thermostat there to keep it out. This cools the temp sender which resides in the front of the manifold and that gives you a cool reading on the gauge. But there is really little or no flow in the heads and liners, and the engine is running hot.

So the question is, why is there inadequate flow in the engine when the thermostat opens? It could be, as mentioned earlier, that the pump is worn out and there isn't enough pressure to overcome the normal flow restriction in the engine. Or it could be that there is a flow restriction in the T fitting underneath the manifold, something like an impeller blade perhaps. Or maybe after 35 or 40 years of life there is a lot of corrosion inside of all the little passages in the engine and it just needs a good cleaning out.

All something to think about this winter!

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Old 28-10-2019, 09:25   #10
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Re: Volvo MD17C cooling issue

Quote:
Originally Posted by peterbeale View Post
I just went though this problem on 41 year old MD 17C and had to take the cooling manifold off and clean out all the tunnels and also the intake pipe connection. All were blocked.
Also have had to get a second hand gear box as the friction material on the original is worn out. No one at Volvo Spain or head office would, or could give me the specifications for the material. Spain said buy a new engine!! Had clutch and break expert put in material, but material did not work. Had my first Volvo engine in 1974 when there service was great. Times and their service has changed!!
Peter,
If you still need it, send me a PM with email address and I can email drawings of the friction material for the RB and MS gearbox.

DougR
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Old 28-10-2019, 13:44   #11
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Re: Volvo MD17C cooling issue

I would suggest watching a few Barnacle Buster Youtube videos. I find with my Volvo MD7b it needs a flush about every 18 months or so. I use a phosphoric acid mix to do the job. Only takes a small amount of calcium build up to cause problems.
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Old 29-10-2019, 02:51   #12
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Re: Volvo MD17C cooling issue

I had this same problem & symptoms with my MD11C (2 cylinder version of the same engine) Doug R is absolutely correct. You will find that the bronze "T" under the exhaust manifold will be blocked as well as most of the passages in the manifold (manifold passages will likely be rusted as well so be careful cleaning them) and all the fine passages in the heads and blocks. This is a 40 year old raw water cooled engine and the black tar like substance that builds up in these passages will blow you away, it certainly did me! Believe me there is no way that barnicle buster or any equivalent will clear this sort of blockage. Take the exhaust manifold and the heads off & then take them home and you can clear all the passages slowly by hand & sight on a bench with drills long wire, scew drivers etc. To save taking the blocks off you should be able to clear the passages insitu with wire etc down to the water drain plugs at base of the blocks and then flush through. Pretty big job with all gaskets etc especially at Volvo prices but certainly very doable. Hope your exhaust manifold is not too badly rusted as these cost over US $1500 for the 2 cylinder variety. Good luck with it and let us know how you get on.
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Old 29-10-2019, 02:54   #13
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Re: Volvo MD17C cooling issue

I forgot to mention the "Marine Diesel" website / blog was a great resource when I did mine just go there & search up MD11C or MD17C and you will get a number of references as it is a pretty common problem with this engine at this age from what I learned.
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