Normal Operating Temperature

Normal Operating Temperature

99 Blazer

90* yesterday, running A/C and my temperature would hit 225 while in stop and go traffic and cool down to 220 when cruising. Would run 210 to 215 with A/C off. Off course when the temp got high the fan clutch locked and cause temp to go higher while killing acceleration.

New 195 thermostat was installed a few month ago and a new red cap has been installed recently.

I guess I will go to a 180 thermostat to see if that helps?


Why the hell did they stop making the thicker rad and go down to a 1" core?

Suggestions?

In my humble opinion, you're running too hot. "Normal" is roughly two clicks left of center. That is where my dash gage runs, and I live just outside of Phoenix.

Simply put, A 180° T-Stat won't help, You probably need a new Rad. These 1" thick cores IMHO plug too easily and are a pain to clean out. Even if you go to a Rad Shop, with the Oil cooler on one side and the Tranny cooler on the other, they're a "B" to Rod out. You can buy a brand new rad for what a shop will do a Rod Out for.

Good luck.

Rick,

Been doing this since this new rad was put in. I have a longer commute now and it is much more noticeable.

O.K. If this has been doing this ever since a new Rad was installed, perhaps you have a bad Temp Sensor. If the Temp sensor is good, then IMHO, this engine is running too hot. With a new T-Stat and Rad Cap, and a good clean coolant mix (50-50 max, I assume You aren't running 70-30 coolant mix), you shouldn't see more that 200° - 205° F. I have a new Radiator, Cap, a 195° T-stat, and new Coolant, and stay below 200° F with the A/C on in 90°-100° temps.

The first question is, Is the engine actually running too hot?

Do you have a Scanner that will read DTC's? My OBD II Scanner will give me actual Engine Temps too, which I understand is a different sensor than the one for the dash gage. If you have one or can borrow one, it might be worth a try to see if the temp sensors match.

Question 2, How old is the "New Rad"?

Just trying to help Brother, good luck.

O.K. If this has been doing this ever since a new Rad was installed, perhaps you have a bad Temp Sensor. If the Temp sensor is good, then IMHO, this engine is running too hot. With a new T-Stat and Rad Cap, and a good clean coolant mix (50-50 max, I assume You aren't running 70-30 coolant mix), you shouldn't see more that 200° - 205° F. I have a new Radiator, Cap, a 195° T-stat, and new Coolant, and stay below 200° F with the A/C on in 90°-100° temps.

The first question is, Is the engine actually running too hot?

Do you have a Scanner that will read DTC's? My OBD II Scanner will give me actual Engine Temps too, which I understand is a different sensor than the one for the dash gage. If you have one or can borrow one, it might be worth a try to see if the temp sensors match.

Question 2, How old is the "New Rad"?

Just trying to help Brother, good luck.


Temperatures readings are coming from my scangauge II. Rad was put in when I replaced the engine 3 or 4 years ago.

50/50 mix being run.

O.K. So if both of your sensors are giving you approximately those same (high) temps, I still say you're running too hot.

Here is one last trick to try that I was shown in a Radiator shop. Bring the engine up to its normal running temp, then SHUT THE ENGINE OFF, ONCE THE FAN HAS STOPPED, reach down inside of the fan shroud and feel the radiator cooling fins at the bottom of the rad, then at the top of the rad.

If the bottom section is cold while the top section is hot, that means the bottom section of your rad is plugged up, and you're only cooling with the top half. This is relatively normal as the sediment, rust etc. settles to the bottom of the rad.

This happened on my Jimmy and one of my Blazers. My Jimmy plugged up 15 months after installing a brand new rad.

Here was my problem

http://img844.imageshack.us/img844/1338/img12251j.jpg

Clogged cat

Btw, drove home in traffic about the same outside temp as before and it got to 220 in stop and go traffic with a spike to 224 when traffic would take off and stop but when back down relatively quick to 218 or so. once I started moving got back down to 204 and then to about 198 for a while. Made it back to 215 when I hit some traffic and back roads to my house.

Btw, drove home in traffic about the same outside temp as before and it got to 220 in stop and go traffic with a spike to 224 when traffic would take off and stop but when back down relatively quick to 218 or so. once I started moving got back down to 204 and then to about 198 for a while. Made it back to 215 when I hit some traffic and back roads to my house.

being a 1999 did you use GM APPROVED dexcool or other type of coolant ? mixing coolants can create blockages in the engine restricting flow. appears to me at slow speeds your engine coolant flow is not strong enough to pass proper coolant flow through the radiator.

look inside the radiator the best you can to see if you have crud on the internal coils. if so use an acid cleaner . drain the engine completely then fill with water and flush the system out including the heater core.

If you have a lot of corrosion in the coolant system [Gray metal film on the internal passageways] it is possible the water pump fins are worn.

replace the coolant cap with a new one and be sure the system holds pressure. with no pressure the coolant will boil and the water pump cannot pump air.

O.K. I'll be the first one to admit that I am confused, and that I learned something new. but can someone explain how a clogged cat will cause high temps in the rad? Clogged Cats will cause poor performance etc., but over heating?

O.K. I'll be the first one to admit that I am confused, and that I learned something new. but can someone explain how a clogged cat will cause high temps in the rad? Clogged Cats will cause poor performance etc., but over heating?

a restricted exhaust can cause some extra heat load BUT a properly operating engine cooling system should have NO problem handling it.

a restricted exhaust if bad will even cause hard starting. most times however the restriction gradually sucks the engine power and much LOWER MPG !

This engine has never had dexcool in it. It had a new rad and engine at the same time. New water pump a few month ago.

Clogged exhaust will cause engine temperatures to rise by causing it to work harder and trapping heat in the engine due to the hot gases not escaping as fast.

Only time I had problem with performance or gas mileage was when the outside air temp rose to above 80*.

It now runs like a brand new truck. I think the cat has been bad for a while, but like I said before my commute went from 12 miles to 60 and it didn't have the time to develop the symptoms.

Good to know you found your problem, or at least most of it. I am not convinced that you're out of the woods yet. A properly maintained and functioning cooling system should show a fairly steady temp. My dash gage NEVER spikes over 210° with the A/C on, and in rush hour stop and go Phoenix traffic.

Did you check the bottom and top of the Rad fins to see if there is a temperature difference?

Did you replace the cat or did you just leave the empty shell in place? It is my understanding that when a cat starts to go, the guts of it usually ends up in the muffler.

Good to know you found your problem, or at least most of it. I am not convinced that you're out of the woods yet. A properly maintained and functioning cooling system should show a fairly steady temp. My dash gage NEVER spikes over 210° with the A/C on, and in rush hour stop and go Phoenix traffic.

Did you check the bottom and top of the Rad fins to see if there is a temperature difference?

Did you replace the cat or did you just leave the empty shell in place? It is my understanding that when a cat starts to go, the guts of it usually ends up in the muffler.


Empty cat, no codes.


My next step is looking at the fan.

Sure, check the fan and the fan clutch, if you see streaks of oil coming out of the fan clutch, replace it. With the engine off, the fan should not spin more than 1 revolution when spun by hand.

Anyway, My prediction in the end is that you have a partially plugged Radiator. Between my 2000 Jimmy and my 2001 Blazer, I've seen this 2 or 3 times.

And FWIW, these single row, 1 inch thick rads are junk. They only work when the system is clean, once the coolant gets contaminated, forget it.