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Duramax 6600 Discussion Forum for the Duramax 6600 Diesel Engine, including the LB7, LLY, LBZ & LMM engine specific topics.

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  #1  
Old 10-30-2008, 03:38 PM
01DURAMAX 01DURAMAX is offline
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Default lb7 engine not getting to operating temp

finally received my injectors from gm after waiting 3 weeks for them so i was able to do the injector swap. everything went well, overall not too bad a job. trucks not smokin anymore and running excellent. i have plenty of heat and the coolant level is staying right where it should after bleeding the system several times. it seems as though the coolant system isn't building pressure but as i said the level is staying where it should. oil level is also good. anyone seen this before? could there still be an air pocket somewhere?...i did pull the drain plugs on the block as well in order to change out all of the coolant. again this is an 01 lb7. any help appreciated.

thanx
-Dave

Last edited by 01DURAMAX; 10-30-2008 at 04:24 PM.
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Old 10-30-2008, 05:20 PM
DmaxMaverick DmaxMaverick is offline
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Are the thermostats still original? If so, you should have replaced them when you did your complete coolant service. Now, while you are still messing with it, would be a good time. The originals are old by now, and could be sticking. Especially after a complete coolant change.

If you have air in the system, it will normally vary the coolant tank level, and blow out a lot of coolant. The temp gage will also fluctuate to extremes. If you did the bleed procedure according to the service manual, it should be minimal. An air bubble in the system is more likely to cause an overheat, rather than an underheat.
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Old 10-30-2008, 06:56 PM
01DURAMAX 01DURAMAX is offline
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the thermostats are only about 9k miles old. i thought the same about runnin hot rather than cold but i can't think of anything else it could be. dependind on who you talk to the bleeding procedures are different. in all cases it seems that there have been many probs with purging all of the air out in these motors.
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Old 10-31-2008, 01:06 AM
DmaxMaverick DmaxMaverick is offline
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What bleed procedure did you use?
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Old 10-31-2008, 04:39 AM
01DURAMAX 01DURAMAX is offline
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i opened the bleeder and filled the coolant until the i got no bubbles out of the bleeder and the level in the bottle was correct. i started the engine and with the cap loosely on 1 thread and when the temp read over 175f i revved the engine from idle to 3k rpm in 30 second intervals but it never warmed up over 180f. i opened the bleeder to see if any air would come out but i just got strait fluid. at this point i decided to drive the truck in order to see if i could work the air pocket out if there is one. i took the truck home with me from my shop which is about 40 miles and then back again this morning. still same thing coolant level hasn't changed at all and engine won't warm over 180f. it is cold here approx 28f but it should warm up in that time. its a mystery to me. if anybody has any ideas.
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Old 10-31-2008, 06:49 AM
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Mark Rinker Mark Rinker is offline
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Okay dumb question...is it possible that you aren't getting a good read of your engine temp - i.e. loose/broken sender wire?

Just a thought...
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Old 10-31-2008, 08:19 AM
01DURAMAX 01DURAMAX is offline
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i suspected that as well not a dumb question. but i have the genesys scan tool and the highest reading that i am getting from the tool is 165.
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Old 10-31-2008, 10:40 AM
DmaxMaverick DmaxMaverick is offline
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That's the correct procedure. There's only one effective way to bleed it, and you nailed it. I'd like to hear of the others. I think you can rule out air contamination at this point, due to your procedure and visible results.

I think if you are seeing 175, it's close enough to call it good. The senders and gages are not that accurate, and a dose of fresh coolant may have loosened things up. I'd run it as-is, and watch for changes in trends, rather than the actual number.
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Old 10-31-2008, 10:40 AM
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180 (when looking the somewhat inaccurate dash gauge) is not entirely out of the range of normal when driving in cool weather and the engine isn't loaded all that much.

If you have the factory winter front, I'd install it for a test, or you could test the truck in some other way that loads the engine more (like towing at freeway speeds).

Jim
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Old 10-31-2008, 01:17 PM
kaylabryn kaylabryn is offline
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Have you driven it or are you just letting it idle/reving in one place. A diesel takes forever when not put under aload to warm up. Just a thought.

Mike
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