wow! I used to be a member of the "Blazer Owners" forum and it's been terminated. I posted a lot of helpful repair procedures and pics there.

So anyway, I just replaced the radiator in my '96 LS and wanted to share my experience.

I cheaped out and cut corners, but hopefully it will all turn out well.

I bought new:

1. Upper & lower hoses
2. Thermostat
3. Radiator (cheap Spectra-Premium #CU1826)
4. Radiator cap
5. hose clamps x 4

I did not do any flushing or back flushing of the cooling system like I probably should've

I ran the engine for just a few minutes after shutting the heat OFF and turning the temp control all the way to COLD (I just wanted to prevent having a huge amount of coolant dropping out. Maybe not such a good plan.)

REMOVAL

** Get yourself plenty of rags and paper towels close by and at-the-ready.

** Place a huge catch pan or multiple catch pans under the engine bay because coolant is gonna drain/drop everywhere.

1. **DISCONNECT AND REMOVE THE BATTERY (makes things much easier)

2. Remove the upper fan shroud.
3. Lower fan shroud snaps into a plastic radiator pan/tray. You need to use a flat-blade screwdriver to unsnap the 3 fastening points. Getting this part out of the way requires a fair bit of twisting and pulling but worth it.
4. Remove radiator cap
5. Pull upper hose off of radiator
6. Turn pet-**** CCW about half a turn ( it should pop outward) and drain the radiator
7. Disconnect the reservoir tank hose from nipple by rad-cap.
8. Don't bother with the special GM quick-connect fittings. Go ahead and unscrew the EOC & TOC line fittings directly out of the old radiator.
10. Disconnect the lower rad hose.
11. Pull the old radiator out.
12. Disconnect the lower radiator hose from the water pump (if you want to replace it)
13. Remove the spring from inside the old lower hose and wipe it clean
14. Push and turn the old spring into your new lower hose.

THERMOSTAT / THERMOSTAT HOUSING & UPPER HOSE REMOVAL
15. Remove the one thrumbscrew to loosen the intake hat/hood from the throttle body.
16. Unfasten the cable bracket from the front of the throttle body.
17. Remove the Thermostat-housing and thermostat from the intake manifold.




**There are large rubber grommets on the mounting pegs on the bottom of the radiator. You'll need to remove and re-use those. They get kinda crappy with age, but I don't know where to get new ones.




Pleasant surprises:

1. Very little oil spills out of the Engine Oil Cooler (EOC) and Transmission Oil Cooler (TOC) lines, so you don't have to worry about a big mess with that.

2. You'll only need a couple of gallons of DexCool and water to re-fill the system.

3. If you've fully drained the radiator you can disconnect and remove the lower hose from the radiator and water pump and there will not be that much additional coolant spilling out.

4. The spring inside the lower hose may look rusty/crappy but it's actually rust resistant, so you can wipe it off and re-use it in your new hose!




Unpleasant surprises:

1. The Thermostat housing / outlet pipe was a rusted out mess and I really wished that I had purchased a new one.

2. Many fasteners seemed to be metric while I was expecting standard. ( a 3/4" wrench worked on the TOC fittings and a crescent/adjustable on the EOC)

4. Big pile of dead bugs and foliage in between radiator and A/C condenser. (not good for cooling efficiency)




INSTALLATION

**You may want to drop the lower fan shroud down into place before dropping in the new radiator, but don't lock it into the tray. (It's hard to wrestle that thing in after the radiator is already installed!)

1. Remove the fabric heat shield from the old upper hose and slide it onto the new upper hose
2. Install your new thermostat and housing. (Slide the new upper hose onto the thermostat housing/outlet pipe before bolting the housing down.)
3. Get your new lower radiator hose pushed onto the water pump nipple but don't fully clamp it yet.
4. Make sure to put the old rubber grommets into place in the eyes on each side of the radiator tray. The pegs on the bottom of the new radiator will drop into these.
5. Drop the new radiator carefully down into the grommets.
6. Thread the lower TOC (passenger side) line fitting into the new radiator.
7. Attach the lower coolant hose
9. Thread the lower EOC (driver's side) line fitting into the new radiator then do the same with the upper EOC line.
10. Thread the upper TOC line into the new rad.
11. Make sure that the radiator is comfortably in place and now tighten all the fittings and clamp down all the hoses.
12. Replace the shroud(s)
13. Re-connect the reservoir hose to the rad filler neck.
14. Re-fill the radiator with 50/50 DexCool & water and purge the system (You're on your own here. I probably did it wrong. I don't yet know if I will have trapped air problems. Follow factory service manual procedure if you want to do it correctly.)
15. ?Add coolant to the reservoir (if necessary)?
16. ?Turn heat on and temp control to high.?
17. Replace the battery
18. ?Start engine and watch temperature gauge and watch the filler neck in the top of the rad to see if the coolant level drops. If it drops add more coolant.?
19. ?As engine starts to get warm, you'll need to put the new cap on.?

OK, well I hope this helps somebody do their own radiator replacement with less mystery and fuss in the future. I cleaned up my old Thermostat housing / outlet pipe by scraping it out with a screwdriver and pulling and twisting a rag through it, but wishing that I had ordered a new one to replace it with.

 

*Moved to the Article Submission/Discussion Forum*

 

Just an update:

I drove it today and everything was fine. The temp slowly rose & fell between about 160 and 200. No more of the edging over 210 crap.

It's a shame that there is no coolant-level sensor on the reservoir considering how fast you can seize and destroy your engine if your coolant level drops too far.

 

Update #2:

Had a leakage problem. 1st coolant spewed out of the expansion tank through the relief hose and down thru the passenger suspension control arms area to the ground. There also seemed to be coolant dripping midway down the passenger side of the radiator. This as I was arriving to work which is about 5 to 7 miles after the T-stat opens and the system is only freshly achieved full heat and pressure.

Similar thing happened the next day only not out of the expansion tank but down the passenger side of the radiator.

The sad fact is that people who come to various forums describing such symptoms are half as likely to receive flippant, off-the-cuff diagnoses like "you've got a blown head gasket" as any of a dozen other knee-jerk replies.

Turns out, my new STANT radiator cap seems to be a wee bit out of spec on the geometry and the little tab-hooks that grab the flange on the filler neck were hitting the expansion tank hose nipple and making me think that the cap was screwed on all the way when it wasn't. This prevented the system from being able to suck coolant back into the radiator during cool-down and also meant that the cap wasn't sealing and thus allowing mild-pressure coolant to blow out through the cap and down the passenger-side radiator tank.

It's very important that there be no problems with your cap, expansion tank or the hose running between the filler neck and the expansion tank. I've seen reports of this hose being choked with Dex-Cool crud which would create similar problems eventually leading to an unacceptably low coolant level, cooling failure and a blown/seized engine.

Coolant expands as it gets warmer, that's why it needs to overflow through the spring-loaded pressure seal created between the cap and the special seat/shoulder in the filler neck, then out the filler-neck hose and into the expansion tank. After you shut your engine off, the coolant will cool-down and contract and the resulting vacuum will suck coolant back out of the expansion tank, through the special valve in the radiator cap and back into the radiator to keep it full and free of air. This is why the cap, hose and expansion tank must be free of any leaks and the coolant must be at the correct level.

Thankfully, I didn't start removing my engine heads and with a little fiddling and muscle, got the rad-cap fully tightened. I expect this to cure my problem, but I'll post an update if it doesn't.

 

Pretty good write up, there is a real good video on youtube that explains this as well.

 

Update #3:
I continued to have problems with coolant spewing out through the expansion tank and radiator cap. It even sprayed into my alternator and set that to whining & screeching.

Turned out to simply be the radiator cap. You have to be extra careful with ordering the correct radiator cap and don't trust that the online listing at your favorite Parts Supplier will be correct. 1996 Blazers use slightly different (almost impossible 2 see difference) caps compared to previous years.

I picked up a Stant 10330 cap from Walmart and the problem is solved. No more coolant spewing out in multiple directions..

BTW: with a defective or wrong cap, you will continue to lose coolant until the level drops too low and your engine overheats.

PS: If you hear a gurgling, percolating sound coming from inside your dashboard while sitting in the car idling or driving, your coolant is low and you had better darn well shut-down and get that taken care of.