Resurface head and replace valve seals etc at time of headgasket replacement or not?

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by cdherman, Mar 31, 2026 at 11:40 AM.

  1. cdherman

    cdherman Junior Member

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    OK, I blew my HG with a leaking EGR cooler that I put on to a flawlessly running vehicle. It was burning no oil and having no problems, but the fluid popped the HG.

    It never over heated, in fact never even threw error codes, but I could see steam in the exhaust. Putting a good EGR cooler on did not stop the coolant loss.

    I have the Felpro HG already and a Toyota kit coming with all the seals. Kit comes with new valve seals as well.

    Local place wants $195 to clean head, regrind valves as needed and replace seals. Another $60 to resurface head. Seems fair and they have an excellent reputation.

    But they take 10-14 days and I'd like to keep moving. This vehicle has 150k miles and needs to last another 3 years and perhaps 50k miles. The car was sideswiped so its no beauty anymore but its been reliable and in 3 years my daughter plans to buy a new car.

    I have read lots of threads, but cannot decide whether to re-work the heads or not. I have a good straight edge (accurate to .0001") and feeler gauges, so I will check the head (and the block) for true and check the valves with the brake cleaner trick..... If I find a problem, I'll definitely have the heads worked on.

    But it would be really nice to have my garage back...... What the consensus? I don't need perfect, just running for 3yrs/40 k miles or so........
     
    #1 cdherman, Mar 31, 2026 at 11:40 AM
  2. Mendel Leisk

    Mendel Leisk MMX GEN III

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    Check against flatness spec's with a machinist's straight edge? Just for giggles you check it first with the "straightest edge you've got on hand", trying several. You basically press the straight edge against the face, and try slipping a feeler gauge under at various points.

    Never mind, see you've got straight edge and feeler gauges.

    The flatness specs are in the bottom link in my signature. (on a phone turn it landscape to see signatures)
     
    #2 Mendel Leisk, Mar 31, 2026 at 12:16 PM
  3. frodoz737

    frodoz737 Top Wrench

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    If it was my car...yes...get it done right. It's a GEN III with 150K miles...and the head gasket blew.
     
    #3 frodoz737, Mar 31, 2026 at 12:40 PM
  4. PriusTech

    PriusTech Active Member

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    Just take a paint and body sanding block with 220 grit Wet-o-dry with WD-40 and go over the gasket surface. Do not use a roll-loc disc, it will gouge in and cause low spots. Then check with the straight edge. Machining is not necessary if it's within flatness specs. But machine shops will always do it anyway. While you have it apart it doesn't hurt to do the valve seals although I would use OEM seals. Fel-pro won't last as long.
     
    #4 PriusTech, Mar 31, 2026 at 1:33 PM
  5. cdherman

    cdherman Junior Member

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    Guess I should check and see how much trouble putting in the valve stem seals is. Good point. I'll have toyota seals.

    Aside -- I once had a subaru boxer engine that some idiot had cleaned off the block with a "wiz-wheel" (like a roll-loc disc) and has rounded the aluminum edges. Which resulted in repeated HG failures. Proper way to fix that is to split the boxer block, deck the half blocks and reassemble. What I did: Get a piece of true plate glass big enough for 2 sheets of wet/dry fastened to glass with spray contact cement. Then using wd-40 as lube, I honed that block 180>220>320>400>600. First pass you could instantly see the rounded edges of the cylinders. It was going strong 6 years and 50k miles later, when I sold it.
     
    #5 cdherman, Mar 31, 2026 at 2:23 PM
  6. ASRDogman

    ASRDogman Senior Member

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    Use a razor blade to clean off the head. Maybe a brass brush to clean it up. Then check the head.
    You shouldn't do any sanding. If it's not warped, no need for the machine shop.

    The block is cast iron and it's not going to warp, if it did, you would've known it because the engine wouldn't have worked

    Valve guide seals are easy. You just need the spring compressor and a strong magnet to grab the retaining clips.
    If the valves are leaking, use valve grinding compound with an electric drill and popping the valve, to seat them in.

    You can do that in an afternoon.
     
    #6 ASRDogman, Mar 31, 2026 at 3:18 PM
  7. BiomedO1

    BiomedO1 Senior Member

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    NEVER sand an aluminum head!!!! Use a green plastic brillo pad and elbow grease.

    You can usually borrow a valve compression tool at your local parts store. They will charge your credit card and refund it when you return it. Make sure it's in good working order BEFORE you leave. I've run into a lot of broken/nonfunctional tools. They are usually pretty good about that, but you don't want to get blamed for breaking something that you didn't break.

    I personally wouldn't use a drill with grinding compound on the valves. If they're leaking and it isn't carbon deposits - it needs to be measured and machined; but at 150K - it's probably OK.

    Good Luck...
     
    #7 BiomedO1, Mar 31, 2026 at 4:03 PM
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