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2006 DTS
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Discussion Starter #1
Had this in my temp issue post, but thought a new thread would be good since it's a different topic.

The short version - got a deal on an '06 DTS. Discovered overheating & confirmed combustion gasses in the coolant. Subsequently found a used engine, with less miles & warranty, & decided to do a swap. Eventually, I will get to tearing down the original engine to determine if the problem was just a failing head gasket, or if there's a crack or warping causing the issue.

So my questions: While I have the replacement engine on a stand before doing the swap, what seals, gaskets etc are the weak links that should be replaced?
Already planning to replace brake lines, faulty power steering hose, oil pan & probably valve cover gaskets, plug tube seals etc. Were crank case gaskets a common issue, or oil pan bed plate seals?
 

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2002 Deville and 2009 DTS
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Might want to think about changing the water pump and water crossover while you are at it...It's the PITA to change while engine is in the car.
Depending on how many miles on the engine, maybe even change the tensioner and the pulley on the serpentine belt.

And yes, Crankcase gasket start to weep oil after a while. I was VERY lucky to be able to remove the rear cover without removing or tilting the engine.
Might as well get that out of the way too.
 

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2006 DTS
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Discussion Starter #3
Might want to think about changing the water pump and water crossover while you are at it...It's the PITA to change while engine is in the car.
Been there, done that, still have the hand cramps to prove it....but yes, water pump & all the fun that goes along with it is on my list.

Thanks for the feedback. Had my fingers crossed that crank case wasn't as much of an issue as older models, but I guess better safe than sorry.
 

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Alexandra - 96 SDV Clyde - 15 Silvy
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Yeah the crank case can be a bear, my dad's 06 leaked like a sieve. Car ran great and the leak wasn't catastrophic, but it left a spot on the ground for sure.

Crank case seals,oil pan seals, valve cover gaskets, water pump crossover, oil filter adapter, all of those you should do now, then you'll be set for awhile.

Something else to look at would be the timing chain tensioners. May not be necessary, but you won't have an easier go of looking at them than right now.

Heck you could give the engine mounts and torque strut a gander too. Not saying you have to replace them, but something to bear in mind.

Sorry if I got carried away hahaha. I'm going to be replacing the AC condenser on my Silverado. Seeing as the radiator has a SLOW leak (dumb plastic tanks!), I will be replacing that and the hoses. After working on a Northstar you learn to group repairs when possible!
 

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2006 DTS
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Discussion Starter #5
Need some opinions if I can upload a picture. Doing some tear down and clean up to start valve cover gaskets. Flipped the engine over and this is the remainder of what was dripping out. When I drained the oil there was no evidence of water. Plenty of oxidation on this engine so it's been sitting for awhile. Maybe the result of condensation in the block?
573858

Looks like it also had green coolant rather than Dexcool. So......continue with my gasket replacements and follow through with the engine swap, or send this back and look for another engine?
 

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2006 DTS
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Discussion Starter #6
A bit of follow up. Pulled the oil pan & there was no sludge, but there was a bit of milky oil left. Also captured some of the coolant in a container. Easier to see that it's a mix of Dexcool with something green. Hopefully one of the "universal" versions so no real damage was done. Guess I'll do a leak down test & go from there.
 

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2006 DTS
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Discussion Starter #7
Gave up on the "replacement" engine. After running into milky oil in the pan, a mix of Dexcool & green coolant, & then finding one of the overhead cam lobes with rust & pitting. Figured if I was going to be putting the extra time & effort into an engine, it might as well be the one that I have a clean carfax on already.

Engine is apart. Found the offending holes in the head gasket allowing combustion gases into the coolant. Sending the heads off for resurfacing while replacing all of the other gaskets on the engine.

Next question.....didn't the nylon timing chain "slippers" used to be available apart from the guides? Looks like I have to replace the entire piece in order to freshen everything up.
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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Looks like the guides and slippers are separate - the tensioner shoes are built-in.

 

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2002 Deville and 2009 DTS
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Just thought of another thing while the engine is out... Change the Alternator!
I will be doing that over Thanksgiving weekend.
 

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2006 DTS perf
2006 DTS Performance Lux III
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950 Posts
When the mechanic had my engine out to reseal it I had him change the water pump, spark plugs, belt tensioners , and the belt.
 

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Changing the alternator surely has to be easier with the engine out of the car. I just changed mine along with the power steering pump, a/c compressor (which has since gone bad again!! UGGGHHHH!!), the idler pulley, belt and tensioner assembly. It's not all that easy to do with the engine in. Albeit, instead of removing the the a/c when it went bad, I bypassed it with a 73 and 1/8 inch belt. I am going to take it all back apart this weekend and send the a/c back for a warranty replacement. It really seems like it never ends with this car.
 

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2006 DTS
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Discussion Starter #12
Finally finished & got her started up yesterday for the first time. Had to work for awhile to get some air out of the system, but temperature is now right where it should be.

After the car had been running & warm for awhile (still idling in the shop) the low oil pressure warning came on. Shut down, checked things over, started again with no issues for awhile, then the warning popped on for a moment, then off....followed by what sounded like rocker arm tapping on the back side? So far it's intermittent. No issues on the test ride until pulling back into the shop & the warning popped on again at idle, but went right back off. Popped the hood & after a minute or so at idle the tapping resumed.

Not finding much related to this here so far. Might this be an early side effect of having everything cleaned/de-greased inside & out with all new gaskets? I'll double check the torque on the harmonic balancer bolt, but am certain it was correct before putting the engine back in the car.
 

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2006 DTS perf
2006 DTS Performance Lux III
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950 Posts
Change the oil again check for anything in the oil. also check the oil pressure
 

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2006 DTS
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Discussion Starter #14
Drove the car home last night, roughly 40 minutes on the highway, with no issues & no low oil pressure warning. Though this morning at a couple stop signs exiting my neighborhood, the warning dinged on for a second, then off again. Stopped to double check & all seemed ok. The lifter noise hasn't returned since the test drive the other night. My daily commute is about 95 miles round trip & no other issues this morning. Check engine light was on when I drove home last night, but has now cycled off. Guess I'll pick up some oil additive on the way home & run it for the week & do an oil change this weekend. And yes, check the actual oil pressure to make sure nothing else is going on.

Definitely a different ride than my 03 Deville. My son kept asking if it was better or worse......all I can say right now is that it's different.
 
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