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89 Blazer running hot - at my wits end...

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GlamisGurlie

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I have replaced the radiator (custom from a radiator shop - no plastic), hoses, thermostat, temp sender, gauge, fan shroud, and checked for a blown head gasket. I run a 180 T-stat and it runs at 210. Yesterday it got up to 230 even with the heater on (100 degrees plus here, so that was miserable lol). The only thing left is changing out the water pump and clutch. Wondering if I should switch to a high flow? Never had this problem in the 17 years I've had her until last year. I towed with it all the time and rarely would it get off the 180 mark, even when it was over 100 degrees out. Now I can't tow anything - it's immediately at 230. Thoughts and recommendations on the high flow water pump?

Thanks everyone!
 
Does it heat up during freeway driving or around town stop and go? Or doesn't make a difference?
 
Could be a bad impeller on the WP. If stock was cool for 17 years I see no need for high flow.
 
Possibly a plugged CAT, or a bad O2 causing it to run really lean?

Edit....unplug the temp sender that goes to the computer, that'll put it in open loop and make it run rich.
 
Last edited:
GlamisGurlie said:
I have replaced the radiator (custom from a radiator shop - no plastic), hoses, thermostat, temp sender, gauge, fan shroud, and checked for a blown head gasket. I run a 180 T-stat and it runs at 210. Yesterday it got up to 230 even with the heater on (100 degrees plus here, so that was miserable lol). The only thing left is changing out the water pump and clutch. Wondering if I should switch to a high flow? Never had this problem in the 17 years I've had her until last year. I towed with it all the time and rarely would it get off the 180 mark, even when it was over 100 degrees out. Now I can't tow anything - it's immediately at 230. Thoughts and recommendations on the high flow water pump?

Thanks everyone!
Click to expand...
Put the proper 195* t-stat back in and problem solved. Many people don't understand how the complete system works. Running a hotter t-stat will actually keep it cooler than trying to install a cooler t-stat. I could explain it here but that would take too long.
 
Carcinogen said:
Maybe you should go ahead and explain... A thermostats function is to control minimum temp.
Click to expand...

Only thing I can think of, if the thermostat is too low, it will just stay open all the time and water won't sit in the radiator long enough to cool off.

Maybe?
 
Carcinogen said:
Maybe you should go ahead and explain... A thermostats function is to control minimum temp.
Click to expand...

Ok, i'll try to explain it then. As we all know the cooling systeem consists of an engine block full of water, radiator, t-stat, and a fan system either mechanical or electric. Lets focus on the t-stat for a minute, the t-stat is a "VALVE". So you go out and start your vehicle and the first thing that happens is the engine produces heat, that heat is absorbed by the water in the cooling system. Water is not really flowing until the t-stat (valve) opens when it reaches its predetermined temp. Now we have water flow. The hot water that was in the engine block is now routed out of the engine to the radiator and the water that was in the radiator is now entering the engine block at which time will make the t-stat (valve) close since is cooler than the opening temp of the t-stat (valve). The job of the radiator is to dissapate the heat through the cooling fins by the air flowing through the radiator. If the water wasn't allowed to sit long enough in the radiator for the air flow to cool it suffiecently then the engine will start to over heat because the t-stat will remain open. So at this point we have either bad air flow through the radiator, a bad radiator, a bad or stuck t-stat (valve) or one that is under rated, or if the issue only happens at low speeds or idling then a bad fan system as fans are only required up to around 25mph. There is also the chance of a lower radiator hose sucking closed (it happens but rare). The only other issue could be the wrong water pump (reverse rotation on an 89 versus standard rotation on early models) or the impeller is no longer turning or is rotted off.

Once you grasp the concept of how the repeated t-stat "valve" is supposed to keep things happy the better off you'll be.
 
Also another thing most people overlook is the fact after years and thousands of miles,not only can the radiator get deposits in it that restrict coolant flow and "insulate" the coolant from being cooled sufficiently by the fins--engine blocks also get crud build up that does the same thing,it coats the passages and prevents heat transfer..
Many engines I put new freeze plugs in,had an inch of sandy rusty crud piled up in the water jackets..

Back in the day they used to sell a Dupont 2 part radiator flush/neutralizer powder that you dumped in the radiator and let the engine run awhile,several times if need be,up to the point it got too hot ,then you'd flush that out,and had to put the neutralizer in the water and leave it in awhile,to kill the caustic action of the cleaner..I suspect the stuff was lye based,much like Draino sink drain un-clogger...or maybe steam boiler cleaning solution..

I used that stuff on a few vehicles and man,did the water ever come out looking and smelling like rusty sewage !..though a few times the stuff ended up creating a leak in my radiator or heater core (which was likely due to radiator stop leak being removed-),the engines always ran much cooler after a good douching with that stuff..

A few customers I sold that stuff too ended up having head gaskets fail,the old steel shim OEM ones,after using it,I guess it is strong enough to finish off an old one about to fail--I'd rather have it fail in my driveway,than on an interstate though..

Dont know if its still sold,I haven't seen it on store shelves for a long time..maybe it was determined for aluminum engines,heads,radiators and heater cores,it wasn't the best idea..
 
It works the same way with a 160 as a 195 thermostat, the concept is the same just different temps. Reducing flow will increase temps, it may spend more time in the radiator but it will then also spend more time absorbing heat in the engine.
 
Carcinogen said:
It works the same way with a 160 as a 195 thermostat, the concept is the same just different temps. Reducing flow will increase temps, it may spend more time in the radiator but it will then also spend more time absorbing heat in the engine.
Click to expand...

Believe what you want but I have first hand experience that was learned probably long before you were even born.
 
Don't forget a thermostat is also a calibrated passage even when wide open to control flow which is not the same as a not having one in there alowing too much flow to fast and poor cooling.

If you have always run a 180 and have not had a problem before you already know to check the water pump impeller.
I have had an impeller almost completely rot away but that was a Ford V6 TBird.

I always ran a 180 in my 74 K5 untill I upgraded the Rad and needed to upgrade to a 195 to get enough heat in the winter.

Either way you should run a 195 as factory anyways. The sensors and computers are calibrated as such for optimal performance.

And of course pressure factors in also.
 
There are many factors that influence the results within a cooling system. Design, condition of components, etc.

The physics of this are that water (coolant) takes more energy to heat the cooler it is. The cylinder walls and combustion chamber are the heat source, and surface temps exceed the boiling point of the coolant. Moving cool liquid past the heat source is the only way to prevent or minimize localized boiling.

Ignoring every external factor (coolant composition, condition of cooling system, design of cooling system, etc.) that can possibly influence YOUR results in a closed system, slowing coolant flow only increases boiling at the heat sources and increases the overall coolant system temperature because the system is only so efficient at shedding heat.

As mentioned already, the thermostat governs the minimum temperature. Changing flow by reducing restriction or increasing the volume of coolant moved may change the flow patterns within an engine leading to reduced efficiency.
A thermostat can be used to temporarily offset a marginal cooling system by providing slightly more heat capacity in the coolant.

The system in your truck is designed for a 195* thermostat. If it can't maintain that temperature, do not use a reduced temp thermostat to bandaid it. As you see, a colder thermostat has little bearing on maximum engine temperature.

If you plan to replace the pump, do yourself a favor and pull the impeller cover off, and see what kind of condition it's in. If it looks good, I'd expect no change in your issue..
 
GlamisGurlie said:
I have replaced the radiator (custom from a radiator shop - no plastic), hoses, thermostat, temp sender, gauge, fan shroud, and checked for a blown head gasket. I run a 180 T-stat and it runs at 210. Yesterday it got up to 230 even with the heater on (100 degrees plus here, so that was miserable lol). The only thing left is changing out the water pump and clutch. Wondering if I should switch to a high flow? Never had this problem in the 17 years I've had her until last year. I towed with it all the time and rarely would it get off the 180 mark, even when it was over 100 degrees out. Now I can't tow anything - it's immediately at 230. Thoughts and recommendations on the high flow water pump?

Thanks everyone!
Click to expand...
 
I have an 89, same issues after moving from Colorado to Minnesota. Did all you did then found timing to far advanced for lower altitude. It cured it for me
 
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