81 blazer temp gauge problems

[ngoetz]

I bought a 81 blazer in the end of May. I was gone for the month of June in Germany so now i am back in the states trying to sort out issues with the K5. The truck has about 8 inch of lift and 37" SSR with a rebuild 305 and th350.

It has a radiator from a 90 suburban if that makes a difference (not sure if the suburban radiator is bigger) But anyways the temp gauge never goes above the first mark on the temp gauge. The is no fan shroud on the radiator so i would expect it to have problems cooling but it doesn't raise above the first mark under any circumstance. Does anybody know how to test the coolant temperature sensor?

 

[bradshawtech]

Sounds to me like it does not have a thermostat.

 

[ngoetz]

yeah I was thinking that. But I would rather test a sensor before I have to drain some of the coolant to check for a t-stat. But it must be done I guess What temp t-stat should I run?

 

[gotblazers]

I bought a 81 blazer in the end of May. I was gone for the month of June in Germany so now i am back in the states trying to sort out issues with the K5. The truck has about 8 inch of lift and 37" SSR with a rebuild 305 and th350.

It has a radiator from a 90 suburban if that makes a difference (not sure if the suburban radiator is bigger) But anyways the temp gauge never goes above the first mark on the temp gauge. The is no fan shroud on the radiator so i would expect it to have problems cooling but it doesn't raise above the first mark under any circumstance. Does anybody know how to test the coolant temperature sensor?

I replaced my thermostat with a 180 degree one and it still does that. Only time i ever went past that was climbing up to summit at hollister in 4high loc and even then it was just barely. It just means you got a good cooling system imo ive wheeled mine several times including a 50 mile drive to and from hollister no problem.

 

[bradshawtech]

81 Blazer, Pre injection and computer. I would say 195 degree t stat just to be sure.

On the cylinder head between the exhaust port is where your temp sender is located. It has a single green wire plugged into the sensor, pull the wire and ground it to a good ground with the key turned to the run position and verify that the wiring and the guage are working correctly.
The guage will be pegged all the way to hot if everything is working when you do this test.

 

[ngoetz]

another quick question DO other people run their trucks with out the fan shroud? I assume that the shroud improves the cooling a lot.

 

[bradshawtech]

It is not recommended to run without the shroud for a multitude of reasons.

Fan inefficiencies, dangerous and the air is not pulled through the radiator.

You will notice the lack of cooling mostly in slow speed situations while in traffic or on the trail. If it is a daily driver then on the open road and the highway it should cool well enough.
Are you running the air conditioner as well? If so then it will not operate very well without the shroud for all the same reasons.

 

[ngoetz]

No a/c. With a 3 inch body lift and a radiator from a 90 suburban will any stock shroud fit?

 

[bradshawtech]

The body lift will throw a wrench into the problem.

If it were me I would invest in a electric fan system (search for a thread on windstar fans )

If money is tight then it is going to be tough to find a shroud that will work with the body lift as the radiator is now the same 3" higher than it was in the factory position.

 

[ngoetz]

cfm?

• I was maybe looking into doing a dual fan setup with something from summit. How many cfm does the ratiator need to stay cool?

 

[bradshawtech]

I cant recall the exact CFM rating that you need for a smallblock GM but I bet Summit has a calculator or go to Flex A Lite fan website to see what they recommend.

I have Flex A lite fans on all of my trucks and I love them.

 

[jms]

• I was maybe looking into doing a dual fan setup with something from summit. How many cfm does the ratiator need to stay cool?

If your cooling system is working well as is, leave it alone.

CFM ratings on electrical fans are typically determined without any obstruction of the air flow during testing. Well, a radiator is a serious obstruction...and don't underestimate the demands on the electrical system - those CFMs don't come free...

Of course, it all depends on what you do with the truck. For me, electrical fans worked well in town, in the summer, with the A/C on.
Rockcrawling in the desert heat - not so much.