Owned this 87 blazer for a couple months, haven't drove it a lot, but enough. Was a few minutes out of town and temp gauge was reading high, thought maybe it was off, but decided to turn around and head home to be safe. Got home in time for vent cap to steam so gauge wasn't off. I have replaced thermostat, temp sensor, replaced fan clutch with HD clutch, replaced PS belt, radiator cap and it still will start running hot just idling 10+ minutes. I thought the water pump was fine, it wasn't grinding and didn't have any play, but I'm wondering if that is my issue. There is no coolant being circulated when i run the rig with radiator cap off, just some bubbles once in awhile, and no circulation in the reservoir either. Is that the next step? Replace water pump?
CK5
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Keeps overheating on just idle
- Thread starter DrKessler
- Start date
It is possible the fan on the water pump shaft is loose and not moving water, or it could be rotted away. What did the coolant look like ? What do the tube you can see in the radiator look like?
bp71k5
3/4 ton status
If no coolant is moving, the water pump isn’t working.
Replace the pump, like they said. And the hoses because you are already here.
No disagreement from me, but I'd make darn sure the radiator looks good inside. The water pump is stupid simple, there is almost nothing that can cause it to not pump fluid that isn't visible externally.
I'd budget time to pop the back off the one you remove. If the impeller vanes are corroded to nothing, I'd be tempted to replace the radiator if there is any sign of corrosion, and absolutely replace the antifreeze.
That's assuming the pump is corroded. It's possible the PO installed the wrong water pump too.
I'd budget time to pop the back off the one you remove. If the impeller vanes are corroded to nothing, I'd be tempted to replace the radiator if there is any sign of corrosion, and absolutely replace the antifreeze.
That's assuming the pump is corroded. It's possible the PO installed the wrong water pump too.
bp71k5
3/4 ton status
No disagreement from me, but I'd make darn sure the radiator looks good inside. The water pump is stupid simple, there is almost nothing that can cause it to not pump fluid that isn't visible externally.
Radiator would have to be plugged for no water to move? I guess the thermostat could also be installed backwards? It’s certainly good to check if it flows water since he’ll need to flush it anyway.
No, my thought is that if the impeller is rotten, then the radiator is very likely going to be rotten too. If it was replaced but the pump wasn't, then it could be ok, but it would take a lot of corrosion to eat the vanes off a pump...but I've seen pics, so apparently it is possible. Unlikely IMO, but possible.
Could be the radiators that plugged up, but even at it's worst you'd think *something* would move across the top couple of rows. From my experience you'll see corrosion on the tubes under the cap if the radiator has been abused, and that will be minimal compared to what they look like inside.
You can always run it with straight water (briefly) if you want to make sure it's fixed, without losing a bunch of costly (and toxic) antifreeze.
I recently had to replace my radiator, and to make sure the five year antifreeze works as good as it can, you really need to flush the system well, and drain the block anyway to get a good ratio, so the drain plugs need to come out. Those also can give an indicator as to the abuse the coolant did or did not see, if the drain holes are plugged solid, or a bunch of junk comes out through them.
Could be the radiators that plugged up, but even at it's worst you'd think *something* would move across the top couple of rows. From my experience you'll see corrosion on the tubes under the cap if the radiator has been abused, and that will be minimal compared to what they look like inside.
You can always run it with straight water (briefly) if you want to make sure it's fixed, without losing a bunch of costly (and toxic) antifreeze.
I recently had to replace my radiator, and to make sure the five year antifreeze works as good as it can, you really need to flush the system well, and drain the block anyway to get a good ratio, so the drain plugs need to come out. Those also can give an indicator as to the abuse the coolant did or did not see, if the drain holes are plugged solid, or a bunch of junk comes out through them.
Thermostat was installed with the handle approximately at 2 to 8 if the firewall was 12. In theory parallel to the thermostat housing orientation
One drain hole on radiator and one on block?
There are 2 drain holes on gen 1 small blocks @ in middle just above the oil pan flange. 1 on the radiator lower driverside.
I don't under stand your t stay install description.
I don't under stand your t stay install description.
should be installed like this with the spring end down
This was mentioned above and I wanted to make sure it wasn’t missed
GM has two styles of long snout water pumps. They rotate opposite directions of each other. One is for a V belt set up (which you should have) and one for serpentine set up (started shortly after 87 model years) Mixing them doesn’t work, and can do exactly what is happening now
If you don’t resolve the problem with one of the above mentioned things with the t stat and such, consider replacing the pump and make sure to specify the year of the truck.
it is. that metal ridge that goes from one side to the other on the thermometer is what i was referencing the 2 and 8 o clock orientation and the outlet for the thermometer housing comes off at a angle about 5 o'clock. perhaps the clock reference is a poor choice, ha...
Thermostat rotation location in the port does not matter.
“Indexing” it won’t make much of a difference
but you can check to make sure it opens in a pan of boiling water. Use a spoon, not your fingers
If you have a temp gun or IR camera take a look at the rad and upper/lower hoses after it's warmed up. You should see the temp drop across ea.
i am still on v-belt, this is the pump i ordered, which the description says is for a serpentine belt, but says direct fit for 87 blazer... Shoot, guess i need to call the parts store. Thank you for the heads up on that.
Disregard that maybe... When i think of serp belt, i think of the engine setup just having one belt, but if your just referring to the flat belts vs the v-shaped ones, i have a serp belt that connects main pulley from block to water pump and alternator, so that still might be the proper part.
bp71k5
3/4 ton status
It says that’s standard rotation so would be correct for V-belt but not for serpentine.
