$575 99 Seville project Car overheating
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Northstar Engines and System Technical Discussion Discussion, $575 99 Seville project Car overheating in Cadillac Engine Technical Discussion; ...
  1. #1
    browe is offline Cadillac Owners Member
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    $575 99 Seville project Car overheating

    I normally don't post threads but I am at a stand still on a N* in the 99 SLS
    I purchased this car as a project car, with the knowledge that it had a blown HG

    The first thing I did was do a Cylinder leak down test, and it identified Cylinder 1,3 as having issues. I also did a combustion leak test with the blue liquid at the overflow tank and it showed yellow positive

    So I realize that the engine will need to be drooped and rebuilt sooner or later, but I decided to try a bottle of the snake oil (nanotechnology). Yes I can here the critics coming but I my goal is to get it to run enough to pass inspection...(overheating at the inspection station isn't good, plus its an experiment)

    I made 2 attempts with the stuff
    1st pulled no plugs, followed directions ,and didn't eliminate the gases bubbling through the overflow tank
    2nd removed cylinder 1,3 plugs, disabled fuel injection to cylinders by removing power to the injectors, it made a horrible racket. Followed the directions flushed and filled with coolant....did combustion leak test and showed negative..

    After combustion test testing negative and idling 15 or so minutes gas would build up in the cooling system, pushing coolant out the purge tank...I checked the coolant purge line on the crossover and it was logged with corrosion. I used a 1/16 drill bit to remove the corrosion on the aluminum fitting and have a good stream through the overflow (roughly flowing 1pt per min)....and can see air properly purging from the system when running

    So now I still see gas build up in the system after 30-45 min idle only after the engine gets above 220 deg….combustion test is negative at that point . At least until the coolant gets to the top of the overflow tank. Another symptom is that the heat quits working when this happens…ie a gas bubble in heater core?

    What other possible sources of air introduction in to the cooling system (other than HG) are there?


    Thanks in advance for the input

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  3. #2
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
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    Re: $575 99 Seville project Car overheating

    Another symptom is that the heat quits working when this happens…ie a gas bubble in heater core?
    Yup.

    Sounds to me like you have confirmed that it is a blown HG. Snake oil seldom works and you seem to have confirmed that.

  4. #3
    tateos's Avatar
    tateos is offline Cadillac Owners Connoisseur
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    Re: $575 99 Seville project Car overheating

    With the N* HG problem, the the reason the heater stops working is because combustion gases have entered the cooling system and displaced coolant that should be in circulating in, among other places, the heater core.

  5. #4
    browe is offline Cadillac Owners Member
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    Re: $575 99 Seville project Car overheating

    thanks

    I guess the negative test for combustion gasses in the over flow tank must be due to the coolant scrubbing the hydrocarbons out of the system?

  6. #5
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
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    Re: $575 99 Seville project Car overheating

    Yup. Exhaust gases get vented to the surge tank via the purge line.

  7. #6
    tateos's Avatar
    tateos is offline Cadillac Owners Connoisseur
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    Re: $575 99 Seville project Car overheating

    Most people that have the HG problem go through a period of denial - they do test after test, then replace this thing and that (thermostat, radiator, temp sensor, water pump, fans....) out of disbelief that the HGs can actually be real problem, but it is almost invariably the HGs. The cars have a pretty stout cooling system, so we almost never hear of overheating that wasn't the HGs.
    maeng9981 and maeng9981 like this.

  8. #7
    drewsdeville's Avatar
    drewsdeville is offline Cadillac Owners Master
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    Re: $575 99 Seville project Car overheating

    Keep us updated on the project. Craigslist is riddled with HG Cadillac victims selling for cheap, and I've debated pulling the trigger on one numerous times.

  9. #8
    browe is offline Cadillac Owners Member
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    Re: $575 99 Seville project Car overheating

    I most probably will go to P & P this weekend to get a LD8 northstar. in a 99 Deville .they have a 50% off all in the yard sale...so cost would be $95 with core..dirt cheap...I like to have a 2nd engine to rebuild (winter project) then swap with the one removed ...plus it helps with bolts and sensors and accessory...but I am a little leary on getting an engine that I dont know how it runs.

    Has the N* seen much bottom end issues....rod or main bearings, oil pump? I just got done with a Chrysler 2.7 in a 2001 sebring convertible....challenging timing chain, rod and main bearing issues...but that's why it only cost $1000..The boss loves to drive it!!!!!!!!!

  10. #9
    Submariner409's Avatar
    Submariner409 is offline If it won't run, slap in a big stereo
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    Re: $575 99 Seville project Car overheating

    A Northstar engine that appears clean and dry, head gasket failure notwithstanding, should be a good top overhaul candidate. If the oil pan seal and the halfcase seal are weeping oil, either walk or know that head gaskets are only the beginning. The crank, lower end and oil pump are stout and reliable. Know that the proper torque procedure is MANDATORY for the harmonic balancer: The oil pump is driven by clamping friction between the balancer hub and a crankshaft shoulder - guess at the procedure and you have no oil pressure - none.

    Subscribe the car to www.alldatadiy.com and do some top overhaul homework - it will be necessary.

    Take a long look at www.northstarperformance.com and/or www.huhnsolutions.com

  11. #10
    89falcon is offline Cadillac Owners Fanatic
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    Re: $575 99 Seville project Car overheating

    Quote Originally Posted by browe View Post
    I most probably will go to P & P this weekend to get a LD8 northstar. in a 99 Deville .they have a 50% off all in the yard sale...so cost would be $95 with core..dirt cheap...I like to have a 2nd engine to rebuild (winter project) then swap with the one removed ...plus it helps with bolts and sensors and accessory...but I am a little leary on getting an engine that I dont know how it runs.

    Has the N* seen much bottom end issues....rod or main bearings, oil pump? I just got done with a Chrysler 2.7 in a 2001 sebring convertible....challenging timing chain, rod and main bearing issues...but that's why it only cost $1000..The boss loves to drive it!!!!!!!!!
    If you swap with an SLS engine, you REALLY need to swap the intake cams at the same time....that's the main difference between the two engines....and possibly oil cooler ports on the oil filter mount....if so, swap that also.

    now think about this.......why would a 12 year old cadillac be in the junk yard? If it were a low mileage car that got totaled a couple blocks from the dealership, the engine would be LONG gone. If you are lucky...and I mean VERY lucky, the junked it for a bad suspension....also a very expensive fix.....or possible a collision.

    The bottom end is "stout". I wouldn't lose much sleep about it....and hopefully the car that was $45K off the lot 12 years ago, was well maintained....but unless you "know" it was running great without overheating (I've seen a lot of people blame the "cooling system" for the problems instead of the HGs....it IS the HGs), I'd give a lot of thought to fixing the HGs in a pre-emptive move......and fix the bottom end oil leaks at the same time.....but DON'T touch the rod bearings, and only inspect the mains when you split the block to fix the oil leaks......about $1000 in parts is worth it to me to know I won't be pulling the engine again in the next 100K miles.....

    I swapped a 97 SLS engine into my 97 STS. My kids have beaten the car to death (colorado winters....I feel VERY comfortable with them driving the tank with stabilitrak!)....so the car itself wouldn't be worth much even with a brand new engine.....so I took the chance on an engine I was told "ran great and didn't overheat".....about 5K miles and 5 months into it...so far so good (my kid's school is about 3 miles away). My original engine had over 200K miles, and the bearings look really good when I disassembled it. I only wanted to get 1-2 more years out of the car.....otherwise.....fix it before installation.

  12. #11
    Submariner409's Avatar
    Submariner409 is offline If it won't run, slap in a big stereo
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    Re: $575 99 Seville project Car overheating

    Quote Originally Posted by 89falcon View Post
    If you swap with an SLS engine, you REALLY need to swap the intake cams at the same time....that's the main difference between the two engines....and possibly oil cooler ports on the oil filter mount....if so, swap that also.
    He has an SLS (VIN Y engine, LD8) and is trying another identical engine, so there is no need to swap cams UNLESS the cam lobes and cam follower buckets are worn/dished.

    If the original vehicle was not equipped with the HD Cooling RPO (and almost no SLS was) there's no need to look for an oil filter adapter with the oil cooler line quick connect fittings.

  13. #12
    89falcon is offline Cadillac Owners Fanatic
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    Re: $575 99 Seville project Car overheating

    Ahhh....for some reason I thought he had an STS...

  14. #13
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    maeng9981 is offline Cadillac Owners Connoisseur
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    Re: $575 99 Seville project Car overheating

    $95 for a spare Northstar? That's a steal!

  15. #14
    89falcon is offline Cadillac Owners Fanatic
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    Re: $575 99 Seville project Car overheating

    Quote Originally Posted by maeng9981 View Post
    $95 for a spare Northstar? That's a steal!
    There might be that much in aluminum in it....

  16. #15
    browe is offline Cadillac Owners Member
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    Re: $575 99 Seville project Car overheating

    Picked up the 97 LD8 long block from a 97 De ville Base on Black Friday $124 inc core ( I figure at least 250 lbs scrap aluminum if all goes south.. what a bargain!!!! .besides it gave me good practice on dropping the carriage, accessory disconnection and 6 bolts, and on the ground. man that was easy...It was More difficult separating the tranny from the block...

    accessory's were already picked but I dont in intend to use them since I will be using tall other acc from the 99 LD8

    I think I may be lucky, the car had damage, flipped over, top bashed in and mangled on one side. On removal of the carriage I saw the tranny had a huge crack on the side of the cast housing....engine may be good

    With all the my other projects, helping the boss with x-mas decorations, I haven't had the chance to get the engine on the stand to do a through inspection. I did attempt to remove the torque converter bolts, with a 1/2 impact wrench...wont budge...I will be using 3/4 impact next with a propane torch to heat up the bold to break the locktite....(may be virgin)

    I have been looking at gasket sets
    the head set is the same for 95-99 LD8
    But the conversion set is different PN for the 97 and 99 LD8s
    I know the 99 has liq cooled alt while I assume the 97 is air cooled, correct?
    The last 6 of the VIN for the 97 Deville is 296923....(what was the 97 production of Deville's?)

    What other differences would contribute to the 2 different conversion gasket sets?

    Thanks!

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