Bfenty

History: Bought a new (to me) 1985 Corvette last week. Drove it almost 8 hours home with no issues, I've put over 800 miles on it since I bought it, and she's been running like a champ. I don't know much of the history of the car, other than it is visually in very good shape and seemed mechanically sound the entire time I was driving it.

Now, I drove it to work today (about 60 miles). She was running well, staying around 200 degrees. I stopped at a stop light, and suddenly the temperature started spiking. The pressure valve near the heater core popped off and steam went everywhere. I was lucky enough to stop near a mobile detailer who had just set up, he helped me refill the radiator with water, I let her cool off for a bit, as soon as I started driving the temp climbed again, I hit 240 and managed to get to work and park it. There are no visible leaks, the heater does not blow warm (it's ambient temp air coming out). There was a lot of pressure in the system (thus why the cap popped), which is making me fear a head gasket. I'm now sitting at work, an hour away from home, with a car I can't drive.

Please help!!!

Tom400CFI

You didn't get it full of water/coolant when you filled it back up. Start by getting it full of coolant, w/no air....then re-asses.

It seems more like you're cooling fan isn't working; you stopped and temp went up. Everything after that is unclear, b/c it doesn't seem like you got the system filled properly. No heat = not enough coolant.


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Bfenty

I'm wondering if it could be a stuck tstat? I'm pretty sure I have enough coolant, although the pressure cap blew and I'm not sure if that's something that just putting it back on is enough-do you have to do something special to re-attach that?

c4cruiser

With the engine cold (coolant at 100 degrees F or lower), remove the radiator cap and start the engine. Add enough coolant to bring the level to the top of the filler neck. Watch the coolant level as temps approach 180 to 190 degrees and see if the coolant level drops. That would indicate that the t-stat has opened.

Check the radiator hoses for any sign of them collapsing. Chances are that the t-stat may be stuck closed or a radiator hose has collapsed.

To completely fill the cooling system, do the same as above but once the coolant level drops, raise engine RPM to about 1200 and fill the radiator to the neck, then replace the radiator cap.

I would suggest dong a complete cooling system flush and refill, replace the t-stat, replace both radiator hoses and get a new radiator cap. Also check the fan for proper operation. Also look under the front of the car above the air dam to make sure nothing has become trapped that could cut down or stop airflow into the radiator. Make sure the lower air dams are in place and in good condition.

Bfenty

Thanks for the reply! I don't think the radiator hoses have collapsed-looking at them they appear fine and they feel ok. I know the fan is working and the car has run bone stock temps (fan kicks on at 220 and it's obvious on the temp gauge, tstat opens at 195) right up until today. It was a very sudden change and there's no white smoke that would indicate a head gasket. I think a tstat repair will get me home and then I'll do a full coolant system workover there.

The other thing is that the cap blew on the heater control tubing. I'm wondering if I can just duct tape that off for now or what I need to do. I understand that I will need to fix it RIGHT but for now I just want to fix it well enough to GET HOME.

Bfenty

Bought a t-stat and the tools I need to change it. I'll have to work on it a little later but I'll update what happens.

Bfenty

well, I can't get one of the bolts out. Stupid thing...I'm so close to having this fixed. I should've gotten some pblaster or something...

Tom400CFI

Heat it. Heat works. Heat the manifold around the bolt threads and the bolt will come out. Use heat. Heat works.

Bfenty

I don't have any tools to do that with, though...

FASTAZU

You can try this. Tap the top of the bolt head a few times while trying to loosen it., not hard enough to deform it. If you can't get it off can you remove the hose and see the thermostat? may be able to get a screw driver in and pry it open at least that will get you home.

Bfenty

Good suggestions

Tom400CFI

Couple good ideas right ^there^.

Bfenty

So my brother in law drove out to meet me and brought a bunch of PB Blaster and a breaker bar. We ended up taking the plenum off so we could get the breaker bar onto the bolt, after dousing it in PB Blaster. A couple tugs later and the bolt sheared (We DID let the PB Blaster soak in for about 30 minutes).

So we were able to get the offending thermostat out-great! But now we can't re-attach the housing properly. I bought some RTV at Walmart, so we put a ton of it on this thing, bolted it back down with the one good bolt, and gave it a good 30 minutes to set. We did NOT put the new thermostat in-wanted the engine to run very cool to avoid causing issues.

Drove it home with no issues. She stayed about 160 the whole way (mostly interstate driving at 60 mph). I now will take the whole thing apart and try to get the sheared bolt out-anyone have a good method of doing this?

My first step will be to soak it in PB Blaster for a day or two, I think. I obviously do not want to damage my intake manifold. I suppose I COULD just re-tap the hole? Would love some good advice. Someone above also mentioned heat-I don't have a blowtorch or anything like that available readily but I might be able to get one.

ddahlgren

There is a reason it is called a 'breaker bar'. You did have the heat from the engine if you started it and let it get hot. Buy a propane torch they are cheap and will save a bunch of work down the road. Where did the bolt break is the first part of how to fix it.

Bfenty

Engine heat-didn't think about that. Too late now

it broke with a little bit of the bolt sticking out of the manifold.

The bolt actually had two nuts on the top of it-one was used to hold a ground and the other was holding the tstat housing down. Is that stock? My previous '85 didn't have that, but it also wasn't stock when I bought it.

Bfenty

Image of the bolt before it broke off.

Bfenty

I have these that I’ve never used before-might work? I could also take it to a shop that has done things like this for me before, before I really fawk it up.

hcbph

Here's a couple of thoughts, not having seen what's left of the bolt.

couple of options here, depending on what's left. First is if it's broken below the manifold so in essence you have a hole to deal with.

This has worked better than PB Blaster, Kroil and others: 50-50 mix of ATF and Acetone. Squirt it around the threads, take a punch or comparable and a hammer - hit the end of the bolt to 'shock' the thing and open the space between the threads if you're lucky and allow it through better. You may want to do this multiple times over a couple of days. I've seen this loosen some stuff that had sat outside in the open for decades where the canned stuff didn't even make a dent in it.

Now depending on your skill and tools, get yourself a left twist drill bit smaller than the diameter of the bolt (you can get a set at HF but I won't speak to the quality of them). You want a left twist as that's the direction the bolt unscrews, normal drill will turn in the direction to tighten it instead. Measure the depth of the other bolt hole to know when to stop drilling. Center punch the bolt to have a dimple to start drilling. Mark the bit on the depth to stop at and start drilling slowly. You may luck out and have the bit grab onto the stub and start working it out. If you drill the length of the bolt stub and it's in there yet, then you can try the ez-out. You may want to try some heat 'around' the fitting on the manifold but not the bolt to help loosen things up. Don't go oversize on the hole you drill in case you run into issues there's still some meat let on the broken bolt to work with.

If the old bolt is sticking out above the manifold, you might be able to weld a nut onto it to turn it out.

Now if you don't have any 'warm and fuzzy' feelings doing this, take it to a machine shop and let them remove it for you. It's cost a few bucks but may be cheaper in the long run than potentially damaging the intake.

Just some thoughts. Good luck.

PS if you break off a drill bit or ez-out in the hole, you've just compounded your problems trying to get it out. Be aware of that.

Bfenty

Called the local shop-they said they’d be surprised if it took more than 3 hours for them to get it out, and that’s about $250 in labor. Not cheap but cheaper than a manifold.

Silver85

Steel bolt broken off in an aluminum hole.....things can go sideways in a hurry trying to get it out. I find the biggest challenge is getting the bolt prepped to drill straight so that you don't mess up the threads. You need to establish a dimple in the center for the bit to grab and not wander.

Once it's drilled you can use the easy out VERY CAREFULLY. Soak the bolt overnight with the 50-50 mix described above and then use PLENTY of heat on the aluminum before turning the easy out. They break easily if you apply too much torque. I think it's because they are made from a very hardened steel? Not sure but they are almost impossible to drill out if you break one.

I have never used a heli-coil in aluminum but that might be an option.