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!!

[Injuneer]

And your hose routing matches this?

And you have the correct LT1 t'stat?



http://shbox.com/1/93-94_hoses.jpg

[Darrenmb]

Hoses match that exactly,( the one without oil cooler) the one with blue arrows doesn’t get Hot, t stat being checked tonight! For operation and to ensure correct kind, all the parts I ordered when I built it were for gen2 lt1, but that doesn’t mean wrong stat wasn’t sent......

[Darrenmb]

Just took a peek at my tune, wondering if maybe fans are coming on too soon, fan 1 at 175 and fan2 at 185, guess I need to see what t stat opens at, thought I had a 180, buts possible I went 160....,

[shownomercy]

175 may be a little low, but that wouldn't cause you to overheat.

[Darrenmb]

Sucks having to be at work!! Wanna work on my car damnit!! Only reason I was able to check tune was that It was emailed to me, so I just downloaded tuner pro at work... shhhhh. Lol

[harner]

I recall my 355 LT1 being a bear to bleed air out of. I ended up putting the front end of the car as high in the air as I could to help get the air pocket out. May be worth a try to save you a couple hundred bucks. If you're deadset on replacing a rad, I'd look at the Summit brand aluminum rads. I ran one in my IROC for a while without issues. That was also over years ago so I can't comment on their quality.

[shownomercy]

This has been the greatest help to me for bleeding the LT1. Fill up funnel, let car run until thermostat opens, bubbles come out, and done.

https://www.amazon.com/gp/product/B01I40ZQWE/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

[JOATMON]

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 othef hrs, tonight I am going to pull thermostat and put in pot of water on stove and make sure it’s opening..

My bad, I must have missed the part about the engine being rebuilt. Sooo, it must be a completely stuck thermostat, water pump not pumping, or air in the system as others have suggested. I bought a cooling system vacuum evacuation rig a while back after helping a friend with a LS3 Camaro and using his. It eliminates all the air in the cooling system prior to filling.

[JOATMON]

I bought this one from Amazon
OEMTOOLS 24444 Coolant System Refiller Kit, 5 Adapters | Eliminate Trapped Air, and Test Radiator and Heating Core Lines for Leaks | Universal Adapters to Fit Most Radiator Necks and Coolant Reservoir

[Darrenmb]

Nothing to update, a burst pipe has caused an impromptu bathroom remodel... luckily the jag isn’t a daily driver!

[El Super Kevbot]

Replace the radiator.. I just dealt with this sort of thing, no black stuff but constantly overheating after numerous bleeds, numerous caps. It would drive fine sometimes but any hill or incline and it would skyrocket. It left me stranded in Vegas on my way to phx this summer. I hate going to dealerships but I was left no choice. I told them everything. They did pressure tests and the motor was fine. Turned out the cheap internet radiator that my brother installed when he was trying to figure it out turned out to be ever so slightly warped and cause the cap seals to wear uneven. Made it home to Seattle no problems. I'd bite the bullet and replace the radiator. At least rule it out. Hope this one lasts 28 years.

[Darrenmb]

I have purchased a new 3 row aluminum radiator, and a new t stat, but still working on bathroom, if I stop to work on car, wife will not be happy!!! You know that saying is try.... happy wife, happy life!!!

[Darrenmb]

UPDATE!!!!!!
Because I hate reading posts with an issue but no resolution!! :)
Finally had some time yesterday and got to work on car! It’s a combination issue, I replaced t stat and temps cam
Back down to a normal level with just one fan being called for turning on and off as needed, so car is running properly and cool again, used my ir gun to check everything out and. Although temps are staying between 177 and 183, with both hoses hot, I still have a couple of cold spots in radiator near bottom center, doesn’t appear to be hurting anything but I have ordered a new rad regardless, one I bought was for v6 , had no steam port,
Main issue was faulty tstat though! Onward and upward!!!! Now that temps outside are going up it’s time to evacuate and charge the ax!!!

[shownomercy]

always nice to have it be a simple fix!