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Thread: The ol' Tahoe is down for the count - coolant in cylinder(s)

  1. #201
    Join Date
    Feb 2000
    Location
    Montana
    Posts
    11,117

    Post

    Quote Originally Posted by arveetek View Post
    ...clip...

    First, I made a bypass hose to make a circuit on the oil cooler ports:






    ...clip...

    Casey
    I've spoken to a guy here recently who called to talk about why his 6.5 was losing oil pressure after warming up. It would be fine, then he'd lose almost all oil pressure... We talked about the possibilities I knew about on that first call.
    On the second call I learned sorta accidentally that he had put plugs into the oil cooler line ports on the block. His original lines were leaking and he "didn't think they were necessary". I told him that if the oil cooler line circuit was to become blocked, it'll force a bypass valve to open. I continued by saying that I didn't know what the ultimate consequences would be, but an odd response in oil pressure would be expected...

    Like you, I made a looped bypass when I primed the oiling system on Sarah's 6.5 while it was on the engine stand.
    Jim

  2. #202
    Join Date
    Oct 2001
    Location
    Granby, Missouri, USA
    Posts
    2,977

    Default

    We had our first camping trip of the season this past weekend, and it was the first time I really had an opportunity to work the new engine pretty hard. Overall, I'm really pleased with the performance of the engine and upgraded turbo. I was a bit concerned the HX35 turbo might produce too much boost, but on long, somewhat steep grades with the transmission locked in 3rd and the engine at around 2500 rpm, the boost stayed steady between 10-12 psi with EGT's hitting a max of 1150*. The coolant temps were more stable than before as well; the old engine always ran hot, even with every 6.5L cooling upgrade available. I'm beginning to suspect the coolant passages may have been blocked with sediment. The new engine never even reached the halfway/210* mark. It would start to climb a bit, the engine fan would kick in, and then the temp would come back down to around 185*. This was with the A/C on and the ambient temp about 83*. Much better results than before.

    All in all, even with just a stock build, the engine seems to have more power and pulls strong. There is a bit more turbo lag, though, as it blows a ton of black smoke until the engine can build up a bit more RPM and then the exhaust clears up and just keeps pulling. I can hit 15 psi in the upper RPM range at full throttle, so I do keep my eye on the boost gauge, but it doesn't get that high as easily as I thought it might.

    An intercooler is next on my radar. I want to make sure this engine lives a long life.

    Couple of pics of my rig below. 1995 Tahoe towing a 2017 Springdale 1800BH; trailer weighs approx. 4500 lbs and is 21' long; it's not a huge trailer, but is a pretty good load for a short-wheelbase 1/2 ton vehicle.

    First pic is at Devil's Tower in Wyoming about 3 years ago; second pic is north of Mulberry Mountain in Arkansas:







    Casey
    1995 K1500 Tahoe 2 door, 6.5LTD, 4L80E, NP241, 3.42's, 285/75R16 BFG K02's; 1997 506 block; Kennedy OPS harness, gauges, Quick Heat plugs, and TD-Max chip; Dtech FSD on FSD Cooler; vacuum pump deleted, HX35 turbo, Turbo Master, 3.5" Kennedy exhaust, F code intake; dual t/stats, HO water pump, Champion radiator; Racor fuel filter

  3. #203
    Join Date
    Feb 2000
    Location
    Montana
    Posts
    11,117

  4. #204
    Join Date
    Apr 2001
    Location
    Newberg Oregon
    Posts
    11,694

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    So glad to hear that the little beast is gittenerdone......Makes all the work and rework all worth the effort.....

    Enjoy.....
    (1) 1995 Suburban 2500 4x4
    (1) 1997 Astro
    (1) 2007 Chevy Avalanche
    THIS IS BOW TIE COUNTRY

  5. #205
    Join Date
    Sep 2001
    Location
    Ft. Wayne, In.
    Posts
    501

    Default

    Way to go Casey!
    Sounds like you did a great job!
    d
    Dave, N9LOV
    Member #242
    Dave's Diesels:
    Sold June, 07 '82 1/2 ton 4X4;340k miles
    '97 2 Dr Tahoe, Intercooled,
    Kennedy ECM, 4" Exhaust
    '02 GMC

  6. #206
    Join Date
    Oct 2001
    Location
    Granby, Missouri, USA
    Posts
    2,977

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    After 4,000 miles, fuel mileage is still low. My best tank so far has returned 16.5 mpg, but the last two tanks returned 16.1 mpg. I'm a little disappointed, as I averaged a consistent 17 to 18 mpg with the old engine. But from the other posts I've read, 16 seems to be average. I'm not sure why the mileage would be lower, with a fresh overhaul and new injectors. Perhaps the engine could still use some more break-in time?

    Casey
    1995 K1500 Tahoe 2 door, 6.5LTD, 4L80E, NP241, 3.42's, 285/75R16 BFG K02's; 1997 506 block; Kennedy OPS harness, gauges, Quick Heat plugs, and TD-Max chip; Dtech FSD on FSD Cooler; vacuum pump deleted, HX35 turbo, Turbo Master, 3.5" Kennedy exhaust, F code intake; dual t/stats, HO water pump, Champion radiator; Racor fuel filter

  7. #207
    Join Date
    Jul 2020
    Location
    Montana
    Posts
    367

    Default

    Quote Originally Posted by arveetek View Post
    We had our first camping trip of the season this past weekend, and it was the first time I really had an opportunity to work the new engine pretty hard. Overall, I'm really pleased with the performance of the engine and upgraded turbo. I was a bit concerned the HX35 turbo might produce too much boost, but on long, somewhat steep grades with the transmission locked in 3rd and the engine at around 2500 rpm, the boost stayed steady between 10-12 psi with EGT's hitting a max of 1150*. The coolant temps were more stable than before as well; the old engine always ran hot, even with every 6.5L cooling upgrade available. I'm beginning to suspect the coolant passages may have been blocked with sediment. The new engine never even reached the halfway/210* mark. It would start to climb a bit, the engine fan would kick in, and then the temp would come back down to around 185*. This was with the A/C on and the ambient temp about 83*. Much better results than before.

    All in all, even with just a stock build, the engine seems to have more power and pulls strong. There is a bit more turbo lag, though, as it blows a ton of black smoke until the engine can build up a bit more RPM and then the exhaust clears up and just keeps pulling. I can hit 15 psi in the upper RPM range at full throttle, so I do keep my eye on the boost gauge, but it doesn't get that high as easily as I thought it might.

    An intercooler is next on my radar. I want to make sure this engine lives a long life.

    Couple of pics of my rig below. 1995 Tahoe towing a 2017 Springdale 1800BH; trailer weighs approx. 4500 lbs and is 21' long; it's not a huge trailer, but is a pretty good load for a short-wheelbase 1/2 ton vehicle.

    First pic is at Devil's Tower in Wyoming about 3 years ago; second pic is north of Mulberry Mountain in Arkansas:







    Casey
    Have you researched the made in China Hx35w? I’ve read that they spool faster and have less lag.

    On my work bench is a good used Holset Hx35w and next to it is a made in China one. With my finger, I can spin the compressor wheel easier then the Holset. The Holset is lubed but the China one is not. Could be worth giving it a try on your build.

    On an older build with both Holset and made in China Hx35w lubed the China one for sure had less resistance.

    With my build, I set a strict rule for myself with regards to the Egts. Having the Egt probe on the square dimple of my exhaust manifold, I feel safe to assume that whatever reading I am getting on the pyro gauge, I increase 200 more degrees in my head. Internally, it will always be hotter then what the probe reads. So to be safe, 900 degrees is the max I will ever push it.
    Last edited by 2INSANE; 05-26-2022 at 17:08.

  8. #208
    Join Date
    Jul 2020
    Location
    Montana
    Posts
    367

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    Quote Originally Posted by arveetek View Post
    After 4,000 miles, fuel mileage is still low. My best tank so far has returned 16.5 mpg, but the last two tanks returned 16.1 mpg. I'm a little disappointed, as I averaged a consistent 17 to 18 mpg with the old engine. But from the other posts I've read, 16 seems to be average. I'm not sure why the mileage would be lower, with a fresh overhaul and new injectors. Perhaps the engine could still use some more break-in time?

    Casey
    That’s about what I am getting. I always push it hard.

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