Badly stuck expansion valve bolts

[Diametric]

I'm dealing with the problem of expansion valve bolts that do not want to let go.
There must be a good bit of corrosion on the tips of the threads that were inside the evap housing.
They will turn about 4 turns then lock up solid.

I sprayed them with PB Blaster and right now I'm waiting 1/2 hour to go try again.
If that fails I think I'm faced with drilling the heads off so I can remove the expansion valve then try to get the remaining studs out.

I think the evap core is good (I'll pressure test it) so I was gonna re use it but if the evap core threads strip it's a fairly involved job to remove the dash to replace the evap. Trying to avoid that.

Any trade tips on getting these boogers out?

If so, thanks!

[JohnHere]

Can you get in there with an oxy-acetylene torch (#1 tip or smaller) to heat-up the ends of the studs cherry red? If so, the nuts will come right off. Better wash off all the PB Blaster, though, and have a fire extinguisher ready.

[Diametric]

Can you get in there with an oxy-acetylene torch (#1 tip or smaller) to heat-up the ends of the studs cherry red? If so, the nuts will come right off. Better wash off all the PB Blaster, though, and have a fire extinguisher ready.

Hello JohnHere!

No sir. There is no access to the bolts tips. Maybe if I removed the entire dash assembly I could get to them from the inside of the vehicle. But I'm really wanting to avoid that if possible.

I don't think there are any nuts. AFAIK, the bolts thread directly into the evap core on the other side of the firewall.
So it must be the last three or four threads of the bolts that were exposed to moisture inside the evap housing that corroded and it's that small 3 or 4 threads that are jamming when trying to unscrew them.

I was also thinking that IF I drilled the heads of the bolts off, I could then move the expansion valve out of the way and that just might allow me to heat the bolts with a torch a bit. Still not sure that would do the trick. At least I could get better access to the bolt threads and keep soaking them with PB Blaster then turning them back and forth hoping to eventually free them.

Worst case scenario...I have to remove the entire dash assembly, steering column, mirrors and all the dash fascias and take the dash out then remove the entire HVAC assembly to put a new evap core in there. Tedious but if I have to I will. One of the most tedious things about removing Gen 4 Dodge Caravan dash assemblies is that everything is held together with the most brittle plastic I've ever seen. Trying to unscrew trim screws almost always means breaking off the entire screw stanchion. The trim and fascia parts end up with so many broken pieces that screwing the assemblies back together and reinstallation is near impossible. It is very common when I take these dash assemblies on the older Dodge Caravans apart that I spend one or two days just rebuilding the posts and screw stanchions or cracks in the HVAC face plate assembly. Super brittle. The good news is that once I have done this rebuilding process they usually never break up again. I have 5 Dodge Caravans. All Gen 3 or Gen 4. If you have any kind of Dodge or Chrysler vehicle you probably know exactly what I'm taking about.

These are my thoughts anyway.

[Cusser]

I'm dealing with the problem of expansion valve bolts that do not want to let go.
There must be a good bit of corrosion on the tips of the threads that were inside the evap housing.
They will turn about 4 turns then lock up solid.

I sprayed them with PB Blaster and right now I'm waiting 1/2 hour to go try again.

Since you can turn about four turns, I'd keep trying the PB Blaster and turning through those 4 turns, then more Blaster. That's what I'd do, and be patient...