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Cooling System ‘94 K2500 Suburban

Big T

Big T

Well-Known Member
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Location
Fullerton, CA
Mods on this cooling system include:
  1. Bosch HO water pump 2000 model year w/ spin on fan clutch hub
  2. Hayden fan clutch within the last 5K miles
  3. DMAX 9 blade fan
  4. New OEM style radiator
  5. AC Delco 190 T-Stat
  6. Single t-stat crossover
  7. Green coolant 50/50 mix (no water wetter
Engine runs warmer than expected. Will routinely see 210 on uphill grades.22A1EDF6-937F-4303-85B5-703C0C701D09.jpeg
 
Last edited:
First is make sure you have an issue: factory gauge is notoriously off. Do you have a secondary one to compare either Dash mounted mechanical or through the cap?
Comparison reading from the scanner at the other sensor? (I’m 99% you are past these but best to ask)

Did you flush the engine block when the radiator was done to ensure no rust in the block/heads? Drained plugs on both sides?

100% sure all air bled from system?

Does this have a “tune” for more power?

Do you have an egt on there where you can see if it is egt driven heat?

Is there ever any coolant meeting to be added?
 
How is the condition of the ac condenser fins, also when was the last time the stack was split and blew out with air, including the trans and engine oil coolers?

the reason I ask on the condenser fins is because they can get collapsed over the years and start blocking air flow through the stack. there is also a gap to the passenger side of the condenser where air flow can bypass the stack to the fan.

next question is at what temp is the fan clutch kicking in and can you tell if the fan is in full lock and roaring? on some, not all fan clutches, even when up to temp for them to kick in, when the rpm is up above 2k + the fan will start to slip and unlock lowering the air flow into the stack. this is one of the things I have noticed about my electro-viscous clutch that it stays locked when turned on.


other things you can check is if you have a ray-temp gun. check various places on the radiator and engine to see what you get. this might tell you more info.
 
First is make sure you have an issue: factory gauge is notoriously off. Do you have a secondary one to compare either Dash mounted mechanical or through the cap?
Comparison reading from the scanner at the other sensor? (I’m 99% you are past these but best to ask)

We have GMTD Scantech on a laptop. I does run 5 F lower than the dash gauge. Need to do more testing.

Did you flush the engine block when the radiator was done to ensure no rust in the block/heads? Drained plugs on both sides?

My son did the work here. Did not flush it. While doing recent work on timing chain and gears, the passages are very crusty.

100% sure all air bled from system?

Yes, upper hose gets hard. This has never been an issue.

Does this have a “tune” for more power?

Yes, Buddy 4-position tune. Pretty much stays on stock position where it is a dawg.

Do you have an egt on there where you can see if it is egt driven heat?

Yes
 
BTW: I do have a (chineese made) electro-viscous fan clutch I bought off RA that I have no use for. I had installed it on my truck and it was fully locked in unless I used something to hold the fan in place while starting the engine. then it would unlock until the controller engaged again. I only ran it a week or so until I replaced it with a Delco one.

if you want to try it I have no use for it!

More Information for GPD 2911362

www.rockauto.com
 
dbrannon79 said:
How is the condition of the ac condenser fins, also when was the last time the stack was split and blew out with air, including the trans and engine oil coolers?

the reason I ask on the condenser fins is because they can get collapsed over the years and start blocking air flow through the stack. there is also a gap to the passenger side of the condenser where air flow can bypass the stack to the fan.

next question is at what temp is the fan clutch kicking in and can you tell if the fan is in full lock and roaring? on some, not all fan clutches, even when up to temp for them to kick in, when the rpm is up above 2k + the fan will start to slip and unlock lowering the air flow into the stack. this is one of the things I have noticed about my electro-viscous clutch that it stays locked when turned on.


other things you can check is if you have a ray-temp gun. check various places on the radiator and engine to see what you get. this might tell you more info.
Click to expand...
Cooling stack is clean after the radiator replacement. This is a California car, so not many bugs. Certainly not a busher of grasshoppers.

I'll have to do some test runs to report back on the fan clutch. It is a new clutch.
 
ak diesel driver said:
How hard are we talking? Usually a hard upper hose is an indicator of a head gasket issue
Click to expand...
Les. I haven't been sleeping with it. I've been in Montana for the past 2.5 years and this truck has been in SoCal. Some discussion about this truck heading up to Montana, because my son does not have the time to work on it.
 
quick and easy is to pull the thermostat out and remove the serpentine belt, then start it and watch for bubbles. Don't run it for very long that way 1-2 minutes tops. If you see some you can remove the crossover and repeat to see which head.
 
You dont want circulation. You are trying to let the bubbles work their way up the crossover.


The problem I have with this type test is if it is the heads cracked between the valves (which I promise you have some of with that many miles)
The cracks won’t fully open up until the metal is all the way hot.
To verify it that way becomes dangerous. Get engine hot, open system and remove stat WHILE at the boiling temperature. This is not a pleasant thing.

The other way is getting the system hot, dump pressure, open up and do combustion/ block check. Tells you when there is exhaust seeping into the coolant.


Does ANY coolant ever have to be added?
 
Will L. said:
You dont want circulation. You are trying to let the bubbles work their way up the crossover.


The problem I have with this type test is if it is the heads cracked between the valves (which I promise you have some of with that many miles)
The cracks won’t fully open up until the metal is all the way hot.
To verify it that way becomes dangerous. Get engine hot, open system and remove stat WHILE at the boiling temperature. This is not a pleasant thing.

The other way is getting the system hot, dump pressure, open up and do combustion/ block check. Tells you when there is exhaust seeping into the coolant.


Does ANY coolant ever have to be added?
Click to expand...

No coolant needs to be added
 
If You have an old fan clutch, like @Will L. guided Me.
Drill a hole through an area where when a sheet metal screw is screwed all the way through, it will lock the fan clutch permanently.
Then install the fan onto it, install the complete assembly onto the coolant pump shaft, take it for a drive and see if it then will run any cooler.
The overheating problem on My truck was the fan clutch not engaging. It was a brand new fan clutch.
Just dont use Your new one, it will be destroyed in this process.
I believe I still have the one I locked up. If You need I will mail it to You, just pay postage. No return necessary.
It seems that I always forget a piece of pertinent information when I tell someone about this process.
Will L, help, what am I forgetting ? 🤷‍♂️😹😹😹
 
MrMarty51 said:
If You have an old fan clutch, like @Will L. guided Me.
Drill a hole through an area where when a sheet metal screw is screwed all the way through, it will lock the fan clutch permanently.
Then install the fan onto it, install the complete assembly onto the coolant pump shaft, take it for a drive and see if it then will run any cooler.
The overheating problem on My truck was the fan clutch not engaging. It was a brand new fan clutch.
Just dont use Your new one, it will be destroyed in this process.
I believe I still have the one I locked up. If You need I will mail it to You, just pay postage. No return necessary.
Click to expand...
I can hear the fan engaging. I need to put the GMTD Scantech on it and drive it around.
 
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