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  1. #1

    Default '88 Siverado leaking anti freeze somewhere

    Hello, I'm working on a 1988 Silverado. Here are the symptoms. I have to add anti freeze 2x week. Maybe more in the summer. It smells like antifreeze when the truck is running and water drips from the exhaust pipe, even after the truck has been running for awhile. The heater core is dry and not leaking inside the bottom of the plastic housing. and also you can hear gurgling inside the heater. There are no visible leaks that I can see on the outside the engine or on the pavement. The oil is clean and has no signs that antifreeze has been mixing with it. I'm starting to tear down the engine now. My question is, "Is it a manifold gasket failure, or do I need to go deeper and replace the head gasket?"

  2. #2


    My bet is on the intake leaking at the rear corners. If it gets too bad it will ruin the head gaskets so be sure to thourghly clean the block with brushes and solvent to check for leaks. The headgaskets tend to leak at the corners of the heads and run down the gasket "crack" and fall onto and around the exhaust manifolds. Use some good felpro perma-dry gaskets to take care if it and only use silicone if the cooland pitted the surface and even then just use it to fill the pits.
    Hope this helps ya
    01' 1500 LT Z71 ECSB 5.3L
    line-x'd front brush guard with KC Daylighters, 6000k HID lows and highs, rewired highbeams, Trans-go mild shift kit, custom stainless duals, 3500 dually OEM taillights, K&N CAI. Still have OEM fender flairs and leveling kit in boxes waiting for time.

  3. #3
    Jr. Apprentice
    Join Date
    Feb 2010
    Stroudsburg, PA


    I'd have to agree with that... I just had the exact same thing on my 99... The truck finally came up for state inspection and I asked them to check it out, they found the leak from the rear of the intake. I tried to just keep adding anti-freeze until the weather improved, but it started leaking out the front AND into the oil.
    It's done now, but it seems that every repair on this thing adds a new problem.
    Anyway.. my only other thought (being an 88) could be freeze plugs rusted through. I've only seen that on ONE of my cars over hte past 30 years, but something to consider.
    Bob Hatton
    Stroudsburg, PA
    1999 Suburban K1500, 1992 GMC Jimmy
    1991 Suburban C2500, 1973 Chevy Blazer K15

  4. #4


    x2 on the head gasket
    2000 Sierra Reg. Cab 5 Speed

  5. #5


    +2 on the intake gasket
    2010 GMC SIERRA CREW CAB (Silver) 4x4, ReadyLift 2.5" Level Kit, 305/60/18 Dick Cepek Mud Country, Go Rhino Nerf Bars, Husky Liners front and rear, Bushwacker Bed Rail Caps, Custom tuned. 4:11's

  6. #6


    Hi everyone! Thanks for your input. I've taken your advice and jumped in with both feet. Here's where I am at now. I've taken everything off the engine down to the intake manifold. I have all the manifold bolts out but 3, they sheared off unfortunately. The 2 studs on the passenger side at the front of the engine(they sheared off slightly below the top of the manifold), and 1 on the drivers side also at the front(it sheared off a fraction above the top of the manifold). I have the manifold loose, but I can't raise the end towards the driver's compartment because it hits the oil pressure sensor fitting just right next to it. And the remaining sheared bolts must be long enough yet to keep me from taking off the manifold. What should I do? Can you remove the sensor fitting mounted in the top of the engine and take the manifold off? Or should I try to drill out the sheared studs on one side of the engine and remove it that way. Your help is appreciated.

  7. #7


    Ouch....if possible, I would try to leave as much bolt left as possible, allowing you to grab it and maybe, just maybe remove without drilling it if the sensor looks like it will come off, you may be saving yourself a ton of work getting the broken bolts out. Drilling out the hardened bolts would be my last resort, as you may end up damaging the threads in the heads and learning a lot about thread inserts...
    Dan Dodge
    '97 GMC K3500

  8. #8

    Join Date
    Sep 2010
    everett, massachusetts


    I was gonna reply earlier to say just put some stop leak into the coolant system as long as you do keep the coolant sytem clean and use the max coolant for corrosion protection.

    when these engines get this old this is the norm with what you experienced.. so now studs must be removed. you will need reverse drills and alot of penitrating oil not wd-40. also work the studs out with moderate force. intake manifold bolts usually come out easy. could be someone removed these bollts before and did not use any thread sealant material / could be they used permenent lock tight . if you suspect permenent lock tight you must heat the bolt up with a torch before removal.

    use a piece of metal tubing to act as a guide to drill out the studs. then re-tap or us an easy out if necessary.

  9. #9


    Thanks for your help. I was afraid of that. These 3 bolts had no chance in heck coming out clean. I can take the oil pressure sensor off at the back of the engine, but the brass fitting there hits the lip of the mainfold. I'm treading lightly, hoping that I can reduce the length of stud and simply lift the manifold off while maintaining enough length to get a vise grip on it to get the rest of the stud out. I'm keeping my fingers crossed. I'll let you know what happens.

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