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  1. #1

    Default Hellp!! Coolant always low but no leak.

    Hi guys i need your help. my coolant keeps going low but i have no apparent leak. I read somewhere about the cylinder heads being defective in the 5.3 heads from '01-'06. So I'm hoping thats that's not the case. I have 144k miles on it. also my second problem is oil gets really low to with no leak visible, I changed the oil about less than a month ago and already its almost 2.5 quarts low. please let me know what you think. also my check engine light, and ((brake)) light is on. If you have any questions please feel free to ask Thank you.

  2. #2


    What year is your truck? There is a known problem with the cast tech heads. Most had a "706" stamped on the ear of the head. Here is the TSB: . As far as your brake light and check engine light goes, I would take it to an autoparts store and have them scan it. They do it for free and it will give you a starting point on what to repair. The check engine could be due to low coolant.

    1995 Silverado 4x4
    6" BDS Suspension Lift-3" Body Lift-Add A Leaf in rear -Trailmaster SSV Shocks-Duel Steering Stabilizer Kit -AirAid Cold air intake-
    4.56 Gears with Detroit Auburn Locker-Pro-Comp Traction Bars with duel shocks-Aluminum Skid Plate Kit-38.5" x 16.5" Mickey Thompson Baja Claws-Constant Dropping fuel gauge

    2005 Yukon XL Jet Power Programmer, Bilstein Shocks, Bilstein rear springs, Helwig Anti-sway bars, EGR Window Visors, EGR Hood Shield, Denali Headlights, Headlight harness upgrade, GE NightHawk Bulbs, White Night Rear lighting system, Russell Braided SS brake lines, PowerStop Brake pads, PowerStop cross drilled and Slotted Rotors,
    2002 Silverado ext cab 2wd (Sold)
    2003 Yukon XL (Totaled)

  3. #3


    The info is below. and i had went to a parts store before and they checked it and it gave me the trouble code i dont remember exactly what code it was but if i remember correctly it had something to do with the evap canister. do these go bad? or defective? maybe a broken hose? is it common?? the one that has me asking questions is the brake light. all my brakes are brand new and my fluid isn't low.

    2001 Chevrolet Suburban LS

    5.3l V8, 2WD 148k Mi
    Magnaflow Exhaust
    Volant CAI
    Airraid TBS

    Head Unit: Alpine
    Speakers: 6.5 pioneer 5 ways All Around
    Subs: 1 12" Kicker Solo X 2500W RMS
    Amps: Soundstream TX1.2000D FOR SUB, KICKER 400.4 For DOORS
    3 Farad Capacitor

    06 Silverado Z71 Rims

    Remote Start Alarm
    55W HID Headlights
    07 Suburban Badging

  4. #4


    Is it the abs light or just brake light. The brake light goes one when the parking brake is on or there is a major fault in the system. You may need to go to a shop that has a better code reader they will use it for free usually but ask u to consider having them fix the problem. My local shop usually tells me what they should fix and what I can do easy my self.

    1996 Chevy Tahoe LT 5.7L V8 4X4 205,000+ miles. Built proudly at Janesville Assembly in Janesville, Wisconsin
    Basic mods: Lights all over, bunch of electrical work, and a couple cooling mods.

    Check out my other mods in My Garage:

  5. #5


    It is just the brake light and not the abs. and yeah ill have to go to a shop to have them scan it, how do i find out if i have the defective heads or not?? are they stamped on the heads under the valve covers???

  6. #6


    You will have to read the TSB to identify the heads, the info is right there. "706" is stamped on the outside of the head, not under the valve cover. But, having 706 does not mean that you have or do not have the bad heads. You would need to pull the valve cover and look for the castech symbol as described in the tsb. (looks like a battery) Advance auto parts will scan the engine and brake codes for free. I don't know if autozone has the scanner that will read brake codes. There are multiple evap codes that can point to anything from a bad gas cap, bad valve, to a major leak in the system, so an actual code will be helpful.
    Last edited by Pikey; 12-28-2012 at 12:52 PM.

  7. #7


    Ok so the codes i got are p0446 and p0453 this was at autozone and no there scanners dont pull brake codes lol and i hope when I pull the valve covers it isnt a nightmare

  8. #8


    for the PO446 check this out, it has pictures and park numbers. You can actually search this forum and find a thread about cleaning the valve that you have.

    I found this on the Po453:
    The po453 ispretty straight forward code pointing to a fault in the Fuel Tank Pressure sensor, and if it was already changed, then there was something either done wrong, or a deeper problem. What you are going to need to replace in this case, is going to be, like i say, the Fuel Tank Pressure Sensor. This sensor is mounted to the top of the fule pump assembly, located on top of the fuel tank. The tank will need to be dropped to access this sensor.

    Have you tried replacing the gas cap?

  9. #9


    ok thx for the info ill actually just go and replace the valve with that part that it shows on that website.

    now the fuel pressure sensor thats gonna suck being its a suburban with a huge gas tank lol

    thanks to all of you guys for your info!!!

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