View Full Version : TR4/4A TR4A Heater Control Valve Help

07-14-2009, 09:03 PM
I was replacing the heater hoses on my TR4A and the outlet pipe from the heater control valve was so corroded that there wasnt enough pipe left for the hose clamp. So when I tried to unscrew the control valve it broke. Ive tried heat,easy out,cutting the broken piece with a hacksaw blade and it wont budge. Its like its corroded to the adapter pipe. My question is how is the best way to remove the adapter pipe from the head without any further damage and also if I do get it loose will it come out without hitting the head stud? Thanks

07-14-2009, 09:38 PM
I broke one off as well - if you are careful, you can take a drill to the inside of the pipe and remove as much metal as you can - it is very soft alloy. Then chase everything with a pipe tap and you'll be good to go. I would not try to remove the angle adaptor unless you had too - I've broken one off before and that is worse. It will interfere with the head stud.

07-14-2009, 09:44 PM
Thanks for the fast reply! How did you keep the drilled out particles from getting into the coolant? Would a small amount in the coolant hurt anything? What size pipe tap did you use? Also who sells the best quality control valve or are they all the same? Thanks again.

07-14-2009, 10:01 PM
When I drill out a pipe, I used a step drill. It cleans out the edges really well.

07-14-2009, 10:02 PM
I'm betting there are better ways, but other than grabbing as much debris as I could I didn't worry about the particles that fell in. Probably running a shop vac at the same time would help, or you could very carefully stuff some fabric or other plug into the hole, but there would be the risk of it getting into the engine. In my case, I knew I had a lot of built up material in the engine already so I didn't think a little more would hurt it. And so far, it hasn't!

I haven't heard of any differences in these valves, Moss or TRF would probably be my first stop.

07-14-2009, 10:08 PM
I just remembered I have a set of the step drill bits so I will try those and order a new HC valve. Do you remember which size pipe tap you used?

07-15-2009, 01:34 AM
Sorry, don't recall exactly, but as a guess I'd say 1/4 npt.

07-15-2009, 11:13 AM
Drill and tap is probably your only option, but, the metal shavings will end up in your rad, plugging some of the cooling. They could also cause problems with your thermostat. You might want to drain your cooling system and remove the thermostat, housing, water pump, and hoses. then flush the block every which way you can. You probably need to do this anyways.

07-15-2009, 11:14 AM
I finally removed the broken piece of the heater control valve and Im pretty sure I dont want to do this again! Question. Will a SAE tap clean the pipe threads up or should I go buy a NPT tap? Thanks

07-15-2009, 11:36 AM
You need a pipe thread tap, the threads are tapered. Yours doesn't look too bad though and you might get by with some teflon plumbers paste (or tape).

07-21-2009, 06:06 PM
Just received a new heater control valve and I have a question. The new one seems to stop and catch with a clicking sound kind of like its in a bind. Is it suppose to be this way or should it operate smoothly? I just dont see how the cable will be strong enough to open it. Thanks