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Old 05-12-2012, 02:21 PM   #1
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Losing coolant

Hi Guys-
Got an Isuzu C-240 (four cylinder diesel). When run at idle (600rpm) for 20 minutes or so,
the temperature holds steady at 140, the cooling system does NOT
pressurize, and it loses about a half gallon of coolant.
The bilge is dry and the engine starts and runs easy. Exhaust appears
to be clean water with no color or odor.
What to do?

Thanks-
Eeber
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Old 05-12-2012, 02:27 PM   #2
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I'm clueless, but John Deere says my 4045D shouldn't run at idle for longer than five minutes.

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Old 05-12-2012, 03:08 PM   #3
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Originally Posted by Eeber View Post
Hi Guys-
Got an Isuzu C-240 (four cylinder diesel). When run at idle (600rpm) for 20 minutes or so,
the temperature holds steady at 140, the cooling system does NOT
pressurize, and it loses about a half gallon of coolant.
The bilge is dry and the engine starts and runs easy. Exhaust appears
to be clean water with no color or odor.
What to do?

Thanks-
Eeber
If the coolant is not leaking, it's going out through the exhaust. The cheapest possibility is a blown head gasket. It gets more expensive from there.

If you just filled it and it only did this once, there could have been an air pocket. If you haven't messed with it and it just started loosing coolant, and keeps on loosing coolant, you're going to need a mechanic or a service manual, a good set of tools, and some serious mechanical ability.
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Old 05-12-2012, 03:24 PM   #4
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Mark,
That's a good point but not an OMG issue.

I'd be concerned about the very low coolant temp. My Mitsu warms up quickly to almost 190. Every time. I suspect that your coolant is very likely going from the coolant side of the heat exchanger to the sea water side. I'd check the heat exchanger. And 140 degrees warmed up temp is too cool. Is it a Klassen Engine?
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Old 05-12-2012, 03:57 PM   #5
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Mark,
And 140 degrees warmed up temp is too cool. Is it a Klassen Engine?

Haven't seen "Klassen" anywhere on it.

Maybe a different thermostat will fix the low temp?

There is a new exhaust elbow. Would that be a clue that maybe the
exchanger is bad? Either way, with that much coolant loss, I'll pull
the heat exchanger to begin with. Good guess?

Thanks Gentleman-
Eeber
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Old 05-12-2012, 04:03 PM   #6
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Mark,
............. I suspect that your coolant is very likely going from the coolant side of the heat exchanger to the sea water side.
That's another possibility.
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Old 05-12-2012, 04:16 PM   #7
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Eeber,
No ...the exhaust is sea water.

Yes ...a thermostat should fix the temp. Check your coolant cap (like a radiator cap). I run a 13 lb cap and about 185 degrees. If you only have a 5 pound cap you should probably run a 170 thermostat.

I still think it's the heat exchanger.
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Old 05-12-2012, 04:25 PM   #8
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What happens after 20 minutes? Does it over heat? I know it's a stupid question but just covering the bases. I was loosing about that much and than it would over heat. I replaced the cap to 15lb cap with a good spring and problem solved.
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Old 05-12-2012, 04:44 PM   #9
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What happens after 20 minutes? Does it over heat?

No it does not overheat.

Thanks for the tip on pressure caps.
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Old 05-12-2012, 05:07 PM   #10
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If you are loosing coolant...and it's not in the bilge or the oil...my guess it's going out through the heat exchanger into the exhaust...not too many places it can go.
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Old 05-12-2012, 05:16 PM   #11
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If you are loosing coolant...and it's not in the bilge or the oil...my guess it's going out through the heat exchanger into the exhaust...not too many places it can go.

I'll remove it and send it to a radiator shop for testing/repair.
It looks like it bolts all the way through from the outside?

Thank-you-
Eeber
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Old 05-12-2012, 06:02 PM   #12
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One other question if I may;
What effect, if any, would the fact that the coolant system is not
currently pressurized, have on the operating temperature?

Thank-you-
Eeber
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Old 05-12-2012, 06:45 PM   #13
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Nothing if the temp never gets up above 140. PV=nRT
If volume is constant, which it's not your loosing volume. Coolant is not pressurized. And your temperature is constant at 140. n is a constant and r is a value given for particular liquids. I would say if your temperature is constant and your unit doesn't overheat than the higher your temperature is the more volume you loose. If you let the unit run long enough you will develop more pressure.
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Old 05-13-2012, 05:51 AM   #14
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I would suspect an air lock somewhere in the system.

At 140 there is no use for a pressure cap, so leave it off and keep filling if the coolant level drops.

Long ideling sucks for your ( or any) engine , as does 140F, which will not get rid of combustion products in the oil.

Go for a ride , in gear, and see what the temps become underway.

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Old 05-13-2012, 06:45 AM   #15
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Sorry to say Swampu but the Ideal Gas Law does not apply in eeber's case, his is not a closed gaseous/liquid system due to a liquid leak somewhere that occurs below temperatures where a vapor phase can be established. Think steam engines for a better application.


Eeber (if not an air lock) if you have a TX heat exchanger this would be a good time to check and clean it too. Potential leak areas are:
  • Head gasket or cracked head
  • Exhaust manifold
  • HX
  • Turbo if JWAC
  • Bad plumbing
Also, double check/test your oil for coolant. As suggested get a pro on these engines. Start with boatdiesel.
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Old 05-13-2012, 06:51 AM   #16
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Sorry to say Swampu but the Ideal Gas Law does not apply in eeber's case
That is probably why it took 7 years to get a 4 year degree
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Old 05-13-2012, 08:36 AM   #17
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if you have a TX heat exchanger this would be a good time to check and clean it too.

What's a TX heat exchanger?

Thank-you
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Old 05-13-2012, 11:25 AM   #18
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I do'nt see how it can be an airlock as pressure would rise to some degree.
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Old 05-13-2012, 12:49 PM   #19
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Quote:
Originally Posted by Eeber View Post
When run at idle (600rpm) for 20 minutes or so,
the temperature holds steady at 140, the cooling system does NOT
pressurize, and it loses about a half gallon of coolant.

How do you know it does not pressurize, is there a pressure gauge on the system?

Does the rate of loss continue if you run it longer than 20 minutes? For example, if you ran it for 40 minutes would you lose a gallon?

If it runs longer, does the temperature increase?

Before spending a lot of money on mechanics to remove heat exchangers and send them out for testing, I would get a car parts store radiator pressure tester and check it while not running. I would put a flourescent dye tracer in the coolant and view the exhaust overboard with a UV light as well as check all the plumbing associated with the cooling system.*

If you have a coolant loop in your potable water heater, check the hot water as well.

* You probably won't get anything out the exhaust with the engine shut down so after doing the pressure check with dye, start the engine and watch the overboard with the light. Do this in the dark for best results.

If you see dye glowing, disconnect the transmission cooler inlet and see if the source is upstream (the engine itself or the heat exchanger) or not. If not, then reconnect the inlet and disconnect the outlet from the transmission cooler and check it after pressurizing, dye in that location with none at the inlet shows the cooler is leaking.
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Old 05-13-2012, 02:15 PM   #20
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rick has the right way to do it, it could be the tranny cooler,oil cooler,or the hot water heater if it is heated by the engine. take his advice it good.
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