Help - what is happening here?

[RealJakeMalloy]

Hi -
1976 truck. I am not mechanical at all. Truch has been running great and cool - around 185 water temp. Then in a parking lot heard a "pop" and apparently a bit of smoke. Since then the truck has been running hot despite all fluids being topped. I opened the hood today and saw this...what is this and is this the culprit?

http://https://photos.app.goo.gl/Xn8io2e6F9SGbnMV7

 

[langester]

I tried to open the link and it doesn't seem to be working.

 

[NewDog]

Looks like the tube from your PCV valve has come off (that might explain the pop sound), there should be a tube going from there to your carb.

Not sure if that explains the overheating issue.

The link you posted had an extra "http" in it too. Here's the link that works:

https://photos.app.goo.gl/Xn8io2e6F9SGbnMV7

Posted a snip of the video below.

 

[jdeignan]

Shot in the dark but if thats a PCV valve off of the carb, wouldn’t it create a vac leak, and lean condition? Lean would equal hot temps.

 

[jckkys]

There is no PCV in the picture. There is a breather hose connection on the oil filler cap that has no hose to the air cleaner. Your PCV must be behind the carb plumbed to the rear of the passenger side valve cover. The breather hose isn't a vacuum hose.

 

[m_m70]

^^^
this. although I can't see a hose in the vid so not sure if he had one connected.
but you are correct. no valve connected to carb = vacuum leak = lean = heat

 

[m_m70]

There is no PCV in the picture. There is a breather hose connection on the oil filler cap that has no hose to the air cleaner. Your PCV must be behind the carb plumbed to the rear of the passenger side valve cover. The breather hose isn't a vacuum hose.

this is correct!!

 

[thegreatjustino]

Picture has nothing to do with running hot. As stated, your PVC valve would be in the back of the passenger side valve cover.

Whatever is causing your overheating issue, it's not what's shown in the photo.

 

[DirtDonk]

Just in case there is something visible though, take a couple more shots around the engine compartment and maybe we'll catch something you can use.

Thanks

Oh, and welcome to classicbroncos too!
(in both of the ways that can be taken!%))

Paul

 

[904Bronco]

Looks like he has a pretty good case of blow by out the inlet hose for the PCV system, if so then the blow by is exceeding what the PCV can pull in... if the rig is running in this picture.

Or is it a dirty camera lens?

 

[jckkys]

I don't see any oil on the breather hose nipple. If there was blow by, you would see oil there. The popping noise is most likely a back fire through the carb. These are usually either a lean mixture or a timing issue, including plug wires out of order.

 

[DirtDonk]

And another thing for while you're puttering around the engine compartment, I would ditch the zip-tie holding all the plug wires up hard against each other, and either buy legit wire separators and use those, or you can actually use multiple zip-ties to make wire "separators" rather than just holding them together with one.

With brand new wires this is probably not the issue it used to be, but once they get older and the insulation and other things start to break down, you can get cross-talk between the wires and cause all sorts of funky running things to happen.
Some of which are worst-case scenarios, but most of which will just make the engine run rough.

Paul

 

[RealJakeMalloy]

Thanks, guys. Would there be a cap that would go over that open cover? Maybe what I heard what a cap being blown off and the smoke puff was the initial smoke coming out?

Also going to upload some engine images.

 

[DirtDonk]

Hey Jake. Nope, no cap on that vent.
It would have a rubber hose connecting it to your stock air cleaner housing so that only filtered air would enter the engine. It's literally being sucked into the engine by the PCV valve from the other valve cover. On our engines the valve and the vent are on opposite covers to promote the most efficient suckage of bad gasses out of the crankcase. The swapped sides over the years, but which side does not matter as long as one has the PCV connected to full vacuum and the other has the filtered air "return" connection.

For the V8 engines at least, one of the changes came between '70 and '71 when they put the valve on the driver's side cover and the air intake on the passenger side. I think it remained there all the way through '77.

Paul

 

[RealJakeMalloy]

It seems odd that the hose would just vanish like that - any chance you can show me the proper setup? I should be able to buy some tubing and fix this, no? Even as a total mechanical novice?

 

[DirtDonk]

What air cleaner do you run? Only the stock one, or another type of stock filter would have the easiest way of mounting the breather hose. But aftermarket filters can be retrofit. Just need to know what you have.
And yes, the hose should be readily available I think. Never had to buy that particular size myself, but it should be out there.

As for the pop, I can't see that hose making that sound as it was exiting, stage left... But as for why it would disappear, if it fell off it could easily have fallen to the ground while you were driving. And is probably still in the parking lot!
The "pop" might have been it getting hit by the cooling fan?

Paul