Radiator blockage

[Darrenmb]

Hopefully this is in the right section, if not. Please feel free to move.
Was out the other night and stuck in traffic. Noticed temp gauge was up around the 115 mark ( it’s in a jag so of course it’s in Celsius) which is hotter than I have ever seen it, especially since it was about 60 degrees out! Once car was
mov Again it dropped, by not down to where it normally sits. Figures I had lost coolant somewhere somehow, so next morning I checked and rad was full! Just left car alone at that point as I have been a bit under the weather lately( even got tested for COVID, negative thankfully) anyways, feeing a bit better today so started car and brought up to temp, all seemed ok sitting in driveway, cooling fans came on etc, first one, then the other, but they never shut off! Thought for a
second maybe they are wired backwards or something and are pushing air instead of pulling, but no, air being sucked in! However........
air on outside edge of fans closest edges of radiator was hot, air from middle of radiator where fans are closest to each other was still really cold!
My assumption is blocked radiator, so googling prices, and local parts stores are carrying them at around 90 bucks! Seems a bit too cheap, I don’t want to end up side of road with a new but leaking radiator!! So I’m looking for some input on something a little better, but really don’t want to spend 600 bucks for an all aluminum unit either, anyone know of a happy medium???? Thanks in advance

[Injuneer]

Are you using the Jag radiator or an LT1 radiator? What year is the PCM?

You describe dual fans.... are they controlled by the PCM? Appears you have verified they are both running. Stock programming turns the first fan on (or both at low speed - late 94-97) at 226°F (108°C), and the second fan (or both on high) at 235°F (113°C).

Is the dash gauge accurate - have you checked it against the coolant temp reported by the PCM? Might be a good idea to check the resistance of both coolant temp sensors, and for 12V reference at the gauge sensor and 5V reference at the PCM sensor.

http://shbox.com/1/4th_gen_tech2.html#ect

Have you verified the fan wiring per the factory service manual?

[Darrenmb]

Radiator is from the firebird, pcm is 94 has I want to say a 160 Tstat and Moe has fans on early, using an infrared thermometer gauge is a few degrees off ( as measured at the head where coolant temp sender is mounted), fans are wide correctly and are running in correct direction, do you not think rad is blocked? I tested rad temps with ir gun but not until
Fans were on, so it was messing with reading, radiator definitely cooler in middle than at edges.

[Injuneer]

Rather than guess whether the radiator is blocked and start replacing parts, I tend to prefer to start by collecting a bit of data for diagnostic purposes. I honestly was not aware if it was a stock radiator, and I didn’t remember from helping you in the past what PCM, etc..If you are confident it is actually running that hot, and you are sure all the air is out of the system, block coolant surfaces are clean, suction hose is not collapsing, system is holding pressure, etc., radiator may be the way to go. That’s just my conservative approach to solving a problem.

[Z28pr0jekt]

What waterpump do you have?

[Darrenmb]

Stock firebird pump, cam driven!
Everything is new except the radiator, and nothing else I can think of would explain why it’s only hot on sides and cold in middle. No air in system, heater works fine ( which leads me to believe water pump is pumping), hoses aren’t collapsing, I do not see a lot of flow in radiator, but it’s a little hard to see down in there, as jag hood opens backwards and I don’t get a straight view into it! Coolant in neck does heat up, still looking for a decent upgrade on radiator that isn’t 600 bucks... I found a GM one, for 200 bucks, may go that direction...

[shownomercy]

Are you 100% the coolant is bled from air? Sounds like you have an air pocket to me

[JOATMON]

Darren, You may be experiencing the same issue that I'm having with my swap. After getting it running right and letting it reach full temp to make sure the fans were functioning, when I shut it down it belched some really nasty crap back into the coolant reservoir. I drained the radiator(new) and refilled and drained a couple times, then put antifeeze mix thinking it was ok. Then it belched up more nasty crap. It appears that after this engine sat up with that damned Dex-Cool it created some nasty crap in the block water jackets.
I'm gonna have to pull the thermostat out and give it a good long flushing with some flush chemical.
If your engine sat up for a while before the transplant you may be experiencing the same????

[Darrenmb]

Block was fresh from
Machine shop, hot tanked etc, I am leaning toward air in system now, however no air comes out of either bleeder, just straight coolant, no bubbles or hissing, looks just like opening a faucet!!! Passenger side radiator hose (big one not the steam pipe) is cold! Steam pipe is hot and flowing coolant into radiator!!!
I have to be missing something!!!! I dug further and let it heat up more, ir gun at different spots of radiator still gives readings that are hotter in spots than others, tonight I am going to pull thermostat and put in pot of water on stove and make sure it’s opening..

[Darrenmb]

Yes I’m going back and forth on this, just don’t want to replace stuff that doesn’t need it!!