Surge and Rough Idle

[Lutrova]

Update: I removed the thermostat housing quick to see what I was up against. The bolts are fine. I stripped out the upper bolt hole (thankfully not the lower). So I guess I get to learn how to tap a thread - hopefully without removing the intake again. If the existing bolts are 5/16x18, is the idea to go up one size and tap out 3/8x?? threads?

Also it looks like I did use some RTV with the gaskets, so I'm not sure where I went wrong. Maybe the thermostat slipped down?

[gadget73]

If the threads in the intake are stripped, you may want to use a thread repair insert. A larger bolt probably isn't going to fit through the thermostat housing and I don't know that there is enough material there to drill it. There should be enough material on the intake to allow for an oversize hole to be drilled and tapped for the insert to go in. One other trick, I think the intake holes are blind, meaning they don't go all the way through. That might be a problem with an insert. If you do have to drill through, the bolt and insert will need sealer on it otherwise it will leak coolant around the threads.


honestly if this were on my car I'd remove the intake and do the job on the bench. Way less chance of screwing it up. If the drill runs crooked you're probably going to wreck the intake. Or realistically I'd just swap the intake to one that isn't damaged and cash in the scrap aluminum.


self-stick thermostat gaskets are your friend. Keeps the t-stat from sliding out of position. No RTV required if your mating surfaces are properly clean and flat, which they rarely are unless you carefully file them true again. Usually corrosion and bad gasket removal techniques have them so f'd up that it won't seal.

[Lutrova]

Well pulling and/or replacing the intake would suck. Right now a helicoil repair kit sounds like the most appealing option, and if I screw that up then I guess I'm replacing the intake anyway.

With a self-stick gasket is the adhesive enough to make up for an uneven mating surface, or would you still put RTV between to get a proper seal?

[Rodentkiller]

You may have a warped Thermostat housing you can do ne of two things buy a new housing or sand down the old housing on a large belt sander. the easer way to go is buy a new Thermostat housing.

[Lutrova]

Picked up a MrGasket chrome replacement housing from O'Reilly's. For 11 bucks I figured it couldn't hurt. But it came with this double o-ring that sits in a channel around the coolant passages. Is this supposed to replace a gasket? Is it any good? Is this housing any good?

I suppose if the o-ring is meant to replace a gasket it doesn't hurt anything to try it out. But if a gasket goes in there too, or RTV, then maybe it'd be better to ask first before messing something else up.

[Lutrova]

I successfully repaired the threads with a helicoil. Took the fan, shroud, and upper AC bracket off to get a good angle with my dying Harbor Freight drill. But it's a huge relief not having to pull or replace the intake.

The new, cheapo thermostat housing seems to have sealed up alright. I just used the o-ring provided with no gasket or RTV and haven't seen any leaks. Rodentkiller may have been right that the original housing was warped as I could rock it a bit when set on the garage floor.

So that about wraps up this thread. Engine's running great, which is probably due to vacuum running to the MAP sensor and everywhere else it should. What isn't running great right now is the transmission, but that's a story for a new thread.

Thanks to everyone for the help. It may have taken forever, but I feel like a lot of maintenance has been done and money saved. So long as I did a decent job on the lower intake gaskets...

[gadget73]

flat file, carefully used will find and fix high spots on gasket surfaces. Lay the file across the whole housing and give it a few passes. You'll see shiny spots where the metal is high. Go across the whole thing from both directions until the file is touching evenly. That should make it seal. Or just replace the thing for 11 bucks and carry on with life. i always seem to need to fix this stuff when there is no replacement easily available.

[87gtVIC]

flat file, carefully used will find and fix high spots on gasket surfaces. Lay the file across the whole housing and give it a few passes. You'll see shiny spots where the metal is high. Go across the whole thing from both directions until the file is touching evenly. That should make it seal. Or just replace the thing for 11 bucks and carry on with life. i always seem to need to fix this stuff when there is no replacement easily available.

At what point does one need to worry about the actual thermostat being to thick to fit in a filed housing?

[gadget73]

if you have to remove so much metal that it becomes an issue, you need a new housing anyway. With a file you're probably removing the thickness of a sheet of paper or two. Beyond that its probably too screwed up to fix.

[87gtVIC]

if you have to remove so much metal that it becomes an issue, you need a new housing anyway. With a file you're probably removing the thickness of a sheet of paper or two. Beyond that its probably too screwed up to fix.

I agree.

Only reason I ask as the stock housings I seen have such a little lip already for the t stat that any filing done I would have guessed a gasket and silicone could have sealed.

[gadget73]

the 'stat does sit in a slight recess. The file is mostly about removing burrs from cleaning or slight warping from being installed for a long time. Basically stuff thats just enough to cause a sealing problem.