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I just want to take the time to say thank you for posting this. I have been trying to fix this issue since the beginning of June, 2014. Needless to say, I am not a certified mechanic nor do I have as much knowledge as you do sir. I followed your instructions word for word and in less than 10 minutes I was done. My 2003 3.4 is running like a champ, blowing hot air, and maintaining proper operating temperature. Again, thank you for posting this as you have relieved over 7 months of stress and headaches. I will always be looking for your advice on here when I need help working on my car.

Sincerely,
Ian Allyn
 

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OK all this information is terrific but I have one more question. I have replaced the head gaskets, intake gaskets thermostat radiator and cap. The car is continuing to run on the high side of the normal range. Though it does not overheat the gauge is showing à higher value than I feel comfortable with. We put a laser thermometer on the inlet and outlet sides of the engine and both were under 190°. Should I be concerned with this? It actually runs slightly cooler at an idle then under load. I also have great heat at all times.?
 

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Mr. Handy
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What temps are you seeing on the gauge at max?

If you get the car up to temp (at least 180) and then let it sit idling what does it get up to?

And what does it raise to once driving and under load? And what kind of load are we talking about? I mean obv full throttle or close to it constantly is going to raise the temp. But cruising at a stable speed should lower the temps and not raise them.

Also how did the coolant and old thermostat look as well as the lower intake (coolant passages)? Was there any sort of film/gunk build up?

Fyi: these engines do run a bit hot! As long as you are under 210f I wouldn't worry too much.

I run a Lower temp Tstat but only cause I don't live in a weird climate. I run a 180f stat and have yet to see 200f. But I am likely suffering on mpg because of it.
 

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No gunk or film on lower or upper intake. The temp is slightly higher at cruising speed then at an idle. It does stay below the 3/4 mark on the gauge, but to me that is too high compared to what I have seen in my experience. When I speak of load, I am speaking of 60 to 65 mph.drove for 40miles and it never overheated and sitting at an idle for over 20 minutes the fans never came on. If this is common then I will just put a good set of gauges in rather then depend on the factory ones.
 

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Mr. Handy
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Perhaps for the price of a new OE temp sender change it out and see if that may be the issue.
:eek:k3:

Exactly what I was trying to get at.

However he is saying his fans never come on. And they should be coming on at around 210f. Something isnt right
 

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I agree gents! I would think if the engine was hot, the fans would come on. I will change the sending unit today. If ANYONE has anything that pops into their head I would appreciate any and all ideas! I have been working on engines for way too long and have never seen an engine run cooler at an idle then it does with air rushing through the radiator.
Nothing on this thing is easy to work on either! I guess being an old V8 guy I am very spoiled!
 

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Well Gentlemen, Problem solved, the coolant temp sensor was bad. Though it was changed with the thermostat just before the head gaskets were changed it was failing. I thank you all for the quick and worthwhile info. I was beginning to doubt my own abilities and feared that I did something wrong with the head gasket job. Glad that wasn't it I couldn't even think about tearing that apart again! Again thanks to you all!
 

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Mr. Handy
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Great news!

So are the fans turning on now? And are you seeing lower/more accurate temps?
 

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Mr. Handy
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First off why has the tstat been removed?
 

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Hey....new to the forum....was reading with interest this thread concerning bleeding of the water system.


I have a '05 Impala with the 3.8 liter engine. A couple of weeks ago my wife phoned me and said the water temp was maxed, and there was an alarm sounding in the car. Then, she said temp returned to normal. I flushed the system that weekend, and noticed that the color of the Dex was dirty brown, kind of like muddy water.


That was a couple of weeks ago. My wife uses the car pretty much daily....and had not noted anything abnormal since. Today the same problem returned....this time she also noticed that the heater was also blowing cool air.


I have always performed an air purge by running the engine and heater, keeping the radiator cap off, and adding fluid there. I tried the purge at the purge valve, but kept getting periods where no water at all would come out of the purge. I would squeeze both top and bottom radiator hoses....and ultimately the purge valve would start to bleed dex again. Also....the color of the Dex was once again like muddy water. Also the heater air was warm, but not hot as it should have been.


I had replaced the water pump last year....as well as those 2 plastic water tubes that go into/out of the idler.


So....tomorrow my plan is to perform another flush. Then try and make sure all the air is bled out of the system. Might even swap out the Thermostat.


I am just wondering why this dex is looking like muddy water. Also...as I have never used that purge valve on top of the T-STAT before....wanted to make sure that it should have DEX coming out of it all of the time when open? Another question I have is the location of the drain valve on the radiator....I have been pulling off a hose to drain the fluid previously.....


Thanks....appreciate input....
 

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I haven't read the entire post. But in regards to the 3.4 coolant bleeding I do one additional step. After doing the bleeding at the bleeders I have an assistant rev the engine a bit and hold it there. That will cause the coolant level to drop in the radiator. While the level is low I will add coolant until it is topped off and replace the radiator cap. Then I will tell the assistant to let off the accelerator. This way I know I am 100% air free. If this adds too much coolant it will purge out on its own.

Don
 

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Mr. Handy
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Hey....new to the forum....was reading with interest this thread concerning bleeding of the water system.


I have a '05 Impala with the 3.8 liter engine. A couple of weeks ago my wife phoned me and said the water temp was maxed, and there was an alarm sounding in the car. Then, she said temp returned to normal. I flushed the system that weekend, and noticed that the color of the Dex was dirty brown, kind of like muddy water.


That was a couple of weeks ago. My wife uses the car pretty much daily....and had not noted anything abnormal since. Today the same problem returned....this time she also noticed that the heater was also blowing cool air.


I have always performed an air purge by running the engine and heater, keeping the radiator cap off, and adding fluid there. I tried the purge at the purge valve, but kept getting periods where no water at all would come out of the purge. I would squeeze both top and bottom radiator hoses....and ultimately the purge valve would start to bleed dex again. Also....the color of the Dex was once again like muddy water. Also the heater air was warm, but not hot as it should have been.


I had replaced the water pump last year....as well as those 2 plastic water tubes that go into/out of the idler.


So....tomorrow my plan is to perform another flush. Then try and make sure all the air is bled out of the system. Might even swap out the Thermostat.


I am just wondering why this dex is looking like muddy water. Also...as I have never used that purge valve on top of the T-STAT before....wanted to make sure that it should have DEX coming out of it all of the time when open? Another question I have is the location of the drain valve on the radiator....I have been pulling off a hose to drain the fluid previously.....


Thanks....appreciate input....
Once u get the coolant looking clean I would def replace the coolant temp sensor. They tend to get dirty and fail if u have muddy dexcool.

Drain valve is on passenger side bottom of radiator. Kind of a pita to get at without pulling shields off.


Next time you have the idler assembly off replace those coolant elbows with the aluminum variant. Costs a few $$ more but well worth it.

If your coolant keeps getting muddy I would have to think its being contaminated by either oil (lower intake leaking) or the internal trans cooler is leaking into the radiator/coolant.
 

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Once u get the coolant looking clean I would def replace the coolant temp sensor. They tend to get dirty and fail if u have muddy dexcool.

Drain valve is on passenger side bottom of radiator. Kind of a pita to get at without pulling shields off.


Next time you have the idler assembly off replace those coolant elbows with the aluminum variant. Costs a few $$ more but well worth it.

If your coolant keeps getting muddy I would have to think its being contaminated by either oil (lower intake leaking) or the internal trans cooler is leaking into the radiator/coolant.
g25....thanks for the thoughts. I will look for the valve again today....and of course it is a balmy 43 degrees today so that adds to the "fun".

Will check the price and location of the coolant temp sensor and will replace today (after getting rid of the muddy water....looks like clay....is brownish orange in color). My oil has never shown signs of water intrusion....and I just changed the oil and filter when I was working on the car a couple of weeks ago.

I DID replace those elbows with aluminum ones. Those plastic ones just crumbled when I was taking it apart. Just cheap that Chevy did not use those originally. I thought the pump was leaking as there was anti-freeze all over the passenger side of the engine compartment, but turned out that those tubes were the root cause of that problem.

I am not a mechanic by trade....but have acquired a lot of tools over the years, and outside of a major engine overhaul, am normally willing to at least give most repairs a shot. Certainly have learned a lot on this forum (already) and on other forums for Camaro's, Neon's, Avalanche's...etc....

Between the forums and youtube, have managed to save a lot of $$$ over the years in repairs....

So again, appreciate all the thoughts.
 

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Ok. I replaced the thermostat and the coolant temp sensor after I had flushed the system with water. I did not see anymore brown water.

One bad sign (I believe) was that I located the drain plug on the drivers side of the radiator. I unscrewed it with a 18 or 19 mm socket (what a pain) but nothing came out. I unscrewed the drain plug all the way....could not actually take it out, maybe it is a captive drain plug....but I never saw any liquid come from there. I am guessing this means the radiator is clogged.

I bled the system as described in the procedures above. Seemed like things were working decent.....but then the warm air that was blowing out of the heater turned cooler....and the water temp indicator on the control panel started to fluctuate again from about 10:00 to around 12:00 on the temp dial

I continued bleeding the system using the Tstat bleed valve. While I have not noticed the car overheating.....the heater blows cool air sometimes, and warm air other times. The temp indicator varies as noted above.

I was not losing water before....so not sure if there is a leak or not.
 

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Mr. Handy
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Now it sounds to me like you have a plugged up heater core. As for no coolant coming out of the drain I have no idea. Could be chunks of crap (the stop leak tablets) stuck right by the plug.

What process did you use to flush the system? Have you flushed just the radiator by itself? If not, I would def recommend it.

If your problem still persists I would recommend a heater core flush. And then a pressure check of the coolant system. There could be a small leak and air is being introduced to the system causing air bubbles and the fluctuating temp.

NOTE: After replacing the coolant temp sensor you MUST reset the computer (unhook both battery cables, turn key on, and leave it for a couple minutes). This is an absolute must!!!

I replaced my coolant temp sensor years ago due to sludgy dexcool (my temp gauge wouldn't move at all) and after replacing it the problem persisted. I reset the computer and presto
 

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Retiredpauly mentioned the airlift. I use one at work and I am always confident that there are no air pockets whenever I install a new radiator.
One thing I could never understand is why there isn't a cooling system bleeder on every engine.
 
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