Possibly stuck bolts on thermostat housing of Chevy 305 engine.

[cecho]

I went to remove the thermostat housing the other day and stopped after the bolt turned but did not break loose. It takes around 80 - 90 ft-lb to get the thing to start to move. I'm guessing that the bolt itself is twisting due to the threads being stuck from corrosion. I left it where it was at since I don't really want to deal with a broken bolt at the moment. Any ideas on what I can do? I thought about spraying it down with penetrating oil, but I don't think it would ever get to the threads.

 

[achris]

Re: Possibly stuck bolts on thermostat housing of Chevy 305 engine.

Beat it with a hammer, heat it with a hot spanner... If it still won't play, drill the head off and deal with the stud.

Chris....

 

[cecho]

Re: Possibly stuck bolts on thermostat housing of Chevy 305 engine.

Oh well, that's what I really wanted to avoid. I don't find drilling out bolts to be very fun. I don't really need to go in there. I'll just wait until I have to. I guess I can put PB blaster on it every day for a few months and hope for the best.

Maybe a couple of molecules will find there way under the head and down the shaft of the bolt and maybe those will make the difference.

 

[achris]

Re: Possibly stuck bolts on thermostat housing of Chevy 305 engine.

Oh well, that's what I really wanted to avoid. I don't find drilling out bolts to be very fun. I don't really need to go in there. I'll just wait until I have to. I guess I can put PB blaster on it every day for a few months and hope for the best.

Maybe a couple of molecules will find there way under the head and down the shaft of the bolt and maybe those will make the difference.

I didn't say to drill the bolt out... I said drill the head off and then take the housing off the stud, then deal with the stud. Often removing the load from the threads is enough to allow them to turn.... You can also get heat into the threads of the bolt a lot easier and more accurately. Often whatever is holding it in there will break free once it has been dried out and is less 'sticky'....

Chris.....

 

[Scott Danforth]

Re: Possibly stuck bolts on thermostat housing of Chevy 305 engine.

you can spray all you want, however there is no path for oil to get to the threads. in this case, drill a small hole in the head of the bolt, just off to the side of center by .2" (its a 3/8" bolt). this will be an oil access hole to get your PB blaster or Kroil, or what ever in there by the threads.

However I found that a few well placed "taps" with a hefty hammer on the head of the bolt usually breaks the corrosion loose.

then it that doesnt work, you will be removing the head of the bolt like Chris mentioned.

 

[ENSIGN]

Re: Possibly stuck bolts on thermostat housing of Chevy 305 engine.

Heat the thermostat housing around the bolt.

 

[Augie56]

Re: Possibly stuck bolts on thermostat housing of Chevy 305 engine.

Cecho, my thermostat housing bolts were very "sticky" to remove this off-season, as well (1979 Merc 228 / GM 305). I had the same thoughts as you when I replaced my thermostat ("sure hope I don't snap this bolt in two" and "sure hope the t-stat housing doesn't crack").

Well, I hoped for the best and eased them loose the most gently way I could and everything was fine. The threaded areas were sure corroded, so I wire-wheeled them clean and lightly coated them with 3-1 oil before re-installing. No leaks and all's good.

I don't know if I'd be quick to try to use heat, though....too close to the carb and you might warp the t-stat housing, which may cause it to not seal up properly. If it breaks when you try to free it up, then so be it...much easier to remove a stud than replace a t-stat housing or cause a fire/explosion.

 

[Hoosmatroos]

Re: Possibly stuck bolts on thermostat housing of Chevy 305 engine.

Try to wiggle with your wrench. Bit loose, bit tighter. Hopes that breaks the corrosion. But first try to hammer that sucker on the head

 

[Bondo]

Re: Possibly stuck bolts on thermostat housing of Chevy 305 engine.

Oh well, that's what I really wanted to avoid. I don't find drilling out bolts to be very fun. I don't really need to go in there. I'll just wait until I have to. I guess I can put PB blaster on it every day for a few months and hope for the best.

Maybe a couple of molecules will find there way under the head and down the shaft of the bolt and maybe those will make the difference.

Ayuh,.... I think Chris is sayin' Grind the heads off,...
a Drill could do it I suppose, but my 4" grinder'll do it Quicker,...

Once the heads are ground off, yer just fightin' gettin' the housings Up, 'n off the bolts, which are now studs...
Slappin' 'round it with a hammer usually works...

After ya get the Housings off,... gettin' the rest of the bolts is fairly easy, as they'll be 'bout 4" high...
Plenty to grab with vise-grips, or whatever ya wanta use...

If ya Don't wanta grind the heads off the bolts, Have ya got Air Tools,..??
If so, that opens other possible adventures,....

 

[cecho]

Re: Possibly stuck bolts on thermostat housing of Chevy 305 engine.

Thanks for the help! The threads aren't the problem. It's the shaft of the bout corroded to the housing. I got one out. The second one I think I'm going to have to get out by cutting the head off.

 

[ENSIGN]

Re: Possibly stuck bolts on thermostat housing of Chevy 305 engine.

Heat the housing!!!

 

[cecho]

Re: Possibly stuck bolts on thermostat housing of Chevy 305 engine.

Whelp, heat didn't work. I thought it was free and the head of the bolt came off. Same result as cutting it off at least. Trying to pull the t-stat housing also broke the bolt at the threads though.

I now have a bolt shaft stuck in the t-stat housing and the threads stuck in the intake manifold.

Using the other bolt to try and tap the bolt shaft out of the t-stat hasn't been successful thus far. Also trying to grip what I could from the threaded side in the intake has resulting in nothing but the jaws of the pliers slipping. I guess I need to use an easy-out or left handed drill bit on the threaded portion. Not sure what to do about the t-stat housing yet though. I guess a reverse bit and easy out for that as well. I've been lucky. I haven't had to drill out a bolt since the late 90's. Hopefully it's easier than I remember it was.

Any better ideas?



The reason I went in there in the first place is because the t-stat is sticky and should be replaced. I'm planning on putting a 160 in its place.

 

[Augie56]

Re: Possibly stuck bolts on thermostat housing of Chevy 305 engine.

Heat wasn't my recommendation, it makes steel soft and prone to snap when trying to free bolts/nuts. I always use it as a last, last result. Now you may need a new t-stat housing, too.

If the cost of Easy-Outs and drill bits exceed the cost of a new t-stat housing, you might be better served to not even try to re-use your old t-stat housing, especially after heat has been applied. Just my $0.02.

 

[cecho]

Re: Possibly stuck bolts on thermostat housing of Chevy 305 engine.

I'll at least try to get it out first. I have nothing to loose but time and money.

I didn't try turning it when hot. I also didn't get it all that hot. Just to the point water starts to boil. Well under 300 degrees F. I also waited until it was warm to the touch before turning it. I was only trying to break the corrosion.

The bolt shaft is frozen from corrosion. There's nothing else that would have gotten that bolt out. I don't see any thing that would have gotten it out. I was lucky the other one moved. I'm pretty sure it's going to require drilling the bolt out completely. I don't see why that would require a new $150 - $200 t-stat housing.

Actually... I might only have to drill it part way and then tap it the rest of the way out. The problem with tapping it out now is that I have no guide.



Removing what's left of the threads shouldn't be too bad. I only need to flatten the head of the bolt with a dremel or hacksaw so I can drill it with a left-handed drill bit. I was able to move it slightly with the pliers before it rounded too much

 

[achris]

Re: Possibly stuck bolts on thermostat housing of Chevy 305 engine.

.... I guess I need to use an easy-out or left handed drill bit on the threaded portion.

Why? Why use a left handed drill? Why not just use a normal drill. Just drill it out to the size required by the easy-out and run the easy-out down. It's an open hole (where the threads are left in) so just drill straight through. If the drill jams and runs the threads out though the bottom of the hole, all the better....

Not sure what to do about the t-stat housing yet though. I guess a reverse bit and easy out for that as well.

I have just one word here... Press.....

Chris....
BTW. I wouldn't worry about the steel becoming soft after heating. The thermostat housing isn't going to see much tension, compression or shear in it's life... I think it will survive... :facepalm:

 

[cecho]

Re: Possibly stuck bolts on thermostat housing of Chevy 305 engine.

I can only put out about 1.5 tons of force with my home made press. We'll see if that's enough. The reason I didn't apply too much heat is I didn't want to warp the intake or ruin the intake gasket. As far as using the left handed bits over right handed bits.... I just happen to have a nice set of those... they are sharper than my right handed bits.

What can I put on the bolts to help lower the chance of the bolts corroding that badly? Grease? Anti-seize? RTV sealant?

 

[cecho]

Re: Possibly stuck bolts on thermostat housing of Chevy 305 engine.

My simple press didn't budge it. I drilled about 1/2 inch into the bolt to get a 1/4 " punch in. After hammering on it for a bit one of the nipples shattered. Since I didn't have anything to loose at that point I put all my force into it with a 4 pound sledge. After a LOT of hammering it finally moved about 1/32 of an inch. After a lot more hammering I couldn't budge it at all after that. I found another housing on ebay for $53. It's on its way. I don't expect any problems with removing what's left of the intake bolt. I'll go for it after my hands stop ringing. It feels like I've been mowing the lawn. :lol:

I'm pretty sure I could have drilled it out, but I don't have a drill press nor did I want to spend the time drilling it with a hand drill knowing I could buy another for less than $100. It probably would not have been worth the cost in drill bits to drill out a 4 inch long bolt anyway.

 

[Augie56]

Re: Possibly stuck bolts on thermostat housing of Chevy 305 engine.

Old boats are just fantastic, huh?

 

[cecho]

Re: Possibly stuck bolts on thermostat housing of Chevy 305 engine.

Old boats are just fantastic, huh?

It's a hobby.

I had to drill out both bolt holes in the intake manifold. The other one was too corroded past where the old bolt was for the new stainless steel bolts I bought to fit so I just went ahead and helicoiled both of them.

 

[Scott Danforth]

Re: Possibly stuck bolts on thermostat housing of Chevy 305 engine.

What can I put on the bolts to help lower the chance of the bolts corroding that badly? Grease? Anti-seize? RTV sealant?

At work, we use TefGel its a teflon based lubricant for sealing. we also use 5200 and 4200 fast cure.