View Full Version : Running hot: airlock or new T-stat?
Blew a hose last Saturday and installed new hoses, thermostat, and temp. sending unit on Sunday. The new thermostat is from NAPA, and does not have the 'to radiator' arrow stamped on it. I installed per the Haynes manual, which says 'install spring side into the elbow' which I assumed meant into the motor side. Proceeded to fill radiator with new coolant-only 3 gal-, after which I drove it up onto ramps to facilitate burping out any air in the system. Not much air came out and the fluid level did not drop. Now the gauge shows very high running temps. It will idle to over 200* and got nearly to the red zone after only a few blocks down the road.
I am guessing I installed the thermostat backwards or have airlock.
Thoughts?
Thanks.
If you had not been having Overheating issues then I am suspect that the beast is airlocked.
The spring portion of the stat should go into the crossover.
Make sure that the stat has an airbleed hole in it.
These are many times a little drilled hole with a loose rivet in the hole to allow trapped air to escape into the radiator.
Normally these will burp quite easily and not give issue.
What were the circumstances with the blown hose??
Let us know
Robyn
Subzilla
03-23-2009, 08:04
6 years ago, I put a rebuilt engine in an '84 S10, put a new NAPA thermostat and drove it. From day 1, coolant temps would almost redline until warmed up, then suddenly drop back to normal once the thermostat opened and did this consistently. Replaced thermostat with another brand (can't remember but was probably from Advance Auto) and that fixed the problem.
Change your thermostat. UNLESS, there is an issue causing the blown hose as Robyn is questioning.
The hose issue was that we noticed it badly bleeding green while refueling. A blown hose may be an overly dramatic description. Either way we lucked out; prior to refueling there was no rise in temps. We fueled close to home,(wanted to check mpg's-15 pulling my boat) just a few miles, so I went for it. By the time I pulled in to home the temp was creeping to the red zone, but it never went into the red.
Good to know the T-stat was installed properly, except that the air bleed hole may not be at the top. I was wondering what that little rivet in a hole was for. I think that I'll just get a GM T-stat today and save the NAPA one as a back up. Was trying to get the burb up and runnin' for today, but since that didn't happen, I'll take the time to get an OEM part.
Thanks for the help.
....is turning into a nightmare! My dad is in town, and while I was at work, he went to pick up an OEM T-stat for the the burb. Well, the dealership did not have any in stock, so I reinstalled the NAPA one (with the airbleed pinhole to the top) and put it back together...again. Still gets to warm. I am thinking the NAPA T-stat is junk, rather than an airlock. I observed coolant being pumped back into the radiator via the uppermost heater hose, after the coolant was up to temp where the T-stat would have been open. No bubbles bubbling up. Slowly added more coolant while the motor was running. Temp climbed to about 220*. Took the burb down the block, again the needle kissed the red zone and then dropped right back down to 215-220 and still tries to, but never quite makes it, get into the red zone.
The temp. sending sensor is new too, but I think that is working like it should; my heater is blowing awfully hot air. Hotter than normal, making me think that the gauge reading is true.
Sounds like the NAPA parts is not functioning correctly.
The rivet in the hole is sort of a check valve to stop coolant from flowing through the air bleed hole.?????/
I have seen these with and without a rivet in the hole.
Some early ones did not have a hole at all.
The later trucks with the 6.5 usually have an airbleed screw on top of the stat housing.
???? When the temp goes up high, is the top hose real hot or relatively cool ???
With the coolant rushing out of the heater hose and back into the radiator tank it pretty well eliminates the probability of an air lock.
Have you seen any coolant being blown out the overflow past the radiator cap ??
Sure sounds like a bad T stat.
Keep us posted.
Robyn
Got a thermostat from the dealership yesterday, installed it with the little tiny pinhole up, and I am still getting warm temps.
Grounded my temp gauge to the frame--the gauge spikes all the way to the hot and returns to the cold side after the key is turned on again.
With the NAPA stat, the upper hose was cool even when the motor was warm. With the GM stat, the upper hose is warm with the motor.
No coolant spilling into the overflow reservoir.
Gauge still spikes to near the red zone and will go back down to around 210-215*.
The only thing that I am still wondering is if there is enough coolant in the system. Filled it with 3 gals after the initial thermosat swap and hose replacement. Manaul says capacity is 6 gal. I realize that I did not completely drain the system, but I guess I don't know what would be left after removing the lower radiator hose and the system draining from that point.
Something is amiss here.
Once the engine is warm the coolant level should equalize and the level should be such that you can see it in the top of the radiator neck.
Possibly the gauge sender is whacked.
With the spike of the temp to near red zone and then fall off still sounds like a low level to me though.
Try running with the cap off until the stat opens and see if you canget it to burp itself.
Keep us posted
Robyn
Amiss indeed. I am very frustrated wth this. My parents are in town and my dad wants to head up to Roosevelt to try for walleyes. As it is, he is sort of stuck in town.
Each time that I have messed with the thermostats, just like you mentioned I have run the motor with the radiator cap off until the temps were such that the stat should open. This is when I have observed the flow from the uppermost heater hose. After the motor got up to temp, I would then add more coolant to fill the radiator. I 've tried filling to the top and filling about an inch below the top-why I don't really know, guess I don't want to cause trapped air by filling to the top too fast. I have pulled the truck up on ramps to try and help any air burp out.
I supposed the last thing left to replace would be the new sending unit. Think I'll drive it bit to see what happens (keeping a close eye on the gauge of course), check the coolant level often, and maybe if there is air it will work itself out. If not, then a new sending unit.
Got fed up and took the truck in to the diesel shop. He checked it all out and took temp readings with an infrared gun and all is normal. It's simply a bad gauge. Apparently, the grounding test for a gauge is not an indicator for accuracy.
Thanks all for the help.
Well If I were you I would trot on down to the parts house and get a mechanical type burbon tube gauge and mount on a column bracket Or????????
Screw it into the sending unit hole in the LH head up front. Forget the factory one and use the new one.
Ya needs to know whats up.
best
RC
That's exactly what the shop recommended. It's lunch time now, and I am on my way to look for the set up.
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