1996 b4000 coolant/temp issues?

[North Idaho 5.oh]

Ok, so this is a 1996 Mazda b4000 that I just recently purchased from the original owner (yes it’s absolutely mint) and it had a coolant leak from the right side of the timing cover (as you’re looking at the engine) down by the motor mount.
It does not have oil in the coolant, or vise versa.
I just went through and re-sealed the timing cover, front main seal, water pump, thermostat, lower intake gasket, upper plenum o-rings, valve cover gaskets and all associated gaskets and o-rings….
Now the issue is, I started it up to burp/bleed the system, and it’s not building pressure and the temp gage is going up maybe 1/4 way up and then going straight back to the C… Heat is on and it’s hot, took it for a drive and it’s the same thing.
Maybe I’m over thinking it or maybe it needs to be bled better? Any input would be great!
Oh, it has an aftermarket radiator cap (with the red lever) if that’s a possibility of an issue….?

 

[SenorNoob]

I'd suspect cap unless you have another leak. And getting the air out completely requires getting it almost full. (I "milk" the upper radiator hose with the cap off. You can see air bubbles.) Make sure you have something in the expansion tank. Then drive it till you have heat. When it cools it'll pull coolant from the expansion tank. Assuming of course that you don't have any leaks and a good cap.

You can usually find a parts store with a loaner tool for testing cap and the whole system. Looks like this.

 

[North Idaho 5.oh]

Ok, I’ll try the radiator cap. You’re the second person to mention that… I just finished the re-seal today so now it’s the fine tuning.

 

[North Idaho 5.oh]

And come to think of it, I believe I have one of those coolant pressure testers…. Just have to dig it out lol

 

[gaz]

@North Idaho 5.oh ,

I would not drive this until the cooling system is sorted out and known to be in perfect working condition and order.

Radiator, hoses, water pump, thermostat, heater core, water temp sender, engine temp sender, fan/clutch and the radiator cap.

If I had to replace the ENTIRE cooling system, that is way better, far cheaper and a ton less effort than losing the engine to it.

While the radiator cap is cheap and could be the culprit, I feel thermostat failure, stuck open.

 

[rusty ol ranger]

Its probably the cap but i had a thermostat fail on my 77 F250 once and cause something similar

 

[North Idaho 5.oh]

Ok fellas …. I know it’s been a while but I’m slowly catching up on some projects after the crazy weather we have been having!
I found a donor for the b-series!
Should I do head gaskets or leave it be?

 

[North Idaho 5.oh]

Ended up doing everything. Head gaskets, timing cover, front and rear main seals etc…. Worth it. Preventative maintenance… I have never broken a fuel rail stud till today , I actually broke 2!
Slapped some silver paint on the oil pan and some red on the valve covers… will be putting the engine and transmission in it tomorrow hopefully!

 

[gaz]

I don't recall the 4.0 having fuel rail studs?

 

[North Idaho 5.oh]

This is the fuel rail/upper intake stud…. Best pic I could find. The top (E8) snapped right off

 

[North Idaho 5.oh]

So this truck turned into a complete nightmare…. I ended up pulling the heads and found small cracks in them so with the miles I ended up getting another engine. I found a 97 explorer with 114k miles and was T-boned… got it for $400 and pulled the whole drivetrain and prepped it for install. Got the engine and transmission out of the truck and installed the engine and transmission from the 97 explorer…. Well let’s just say the transmission did what auto transmissions do best and dumped all the fluid and I gave up for a while…. I weighed my options and opted on doing a 5 speed conversion with a 2005 ranger tranny and happened to stumble on another truck just like it (same color too) but with the manual. I used all 5 speed parts so it looks completely factory and shifts like butter. The coolant temp issues were all related to a bad thermostat and a mouse nest (not sure it’s related) in the blower motor…. I resealed the water pump and installed a new radiator cap and thermostat… so far so good…. Looks awesome too! Gonna be my sons first truck since his bronco is taking a little longer than expected