Huh ?
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Itās a confusing concept to me too. Seems like if t-state is removed, the only possibility is a cooler engine. But first consider what Rick says, claims to know the scoop.
A cooler engine temp is detrimental, you want a cooler intake charge for more power. Running the entire engine colder helps keep the intake charge cooler but sacrifices combustion efficiency.
As mentioned above, the idea that āthe faster moving fluid doesnāt have enough time to absorb the heatā is wrong. The reduction in contact time is more than made up for by the increased rate, the reduced boundary layer, and the increased temperature drop from the block to the cooler fluid.
Rickās wrong, except in the case where the open thermostat shuts off the bypass.
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It also seems to me that a faster coolant flow rate through the radiator would increase the amount of cooling, not decrease it. But Iām wondering if some sort of adverse side-effect might occur if the radiator wasnāt able to handle the full coolant flow rate, and the coolant loop backed up.
There seems to be a sort of internet theory about this topic. I wonder if there is any indisputable proof (utube vdo, etc) that removing a carās thermostat (that didnāt overheat prior) immediately causes overheating? Iāve never done that experiment myself.
If the radiator was restricted, then the rate wouldnāt increase, and youād be right where you were with the thermostat in place.
I work with heat transfer (heat exchangers, etc) as part of my background, and thereās no ātoo fastā situation. People confuse contact time with contact volume/time. The volume is the key. Double the flow rate, double the contact volume in a given time, increase the heat transfer.
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Please inform me if I am wrong hereā¦
If the coolant system is full and bled out (no air pockets, everything normal other wise) then that can not be true as you can not compress a liquid, when removing the t-stat all you are doing is causing a constant flow that is not regulated other then the flow rate of the water pump and normal internal restrictions (hoses, passage ways, head gasket holes and block/head coolant holes etc), and will have a flow rate of whatever the water pump can move through out the cooling system (engine/rad)ā¦ The water pump does not flow all the coolant into the rad and leave little in the engine, the amount of coolant is the same through out the entire coolant system no mater what the flow rate isā¦
My point was never about the heat exchange through the radiator itself or how fast the flow through the rad is, but the flow rate across the engine cylinder walls from the heat caused by the power strokeā¦ But thanks to Twin Turbo and Texases I think I understand it better, I am of the old school thinking and evidently not always correct in that thinkingā¦
I guess a very fast flowing river at say 50 degrees would cool a 1000 degree piece of metal down faster then a slow moving river at the same 50 degrees with the same 1000 degree piece if metalā¦??..
Now I know my carbād classic does not like anything under 150 degrees, and I can feel a difference in acceleration loss when the engine gets to/over 200 degreesā¦
Now fuel injected engines normally run better with much higher coolant temps due to computer having preset parameters such as optimal ignition timing etcā¦
That all sounded better in my headā¦ lol
One day I need to take the t-stat out of my classic engine and measure the cylinder wall and header temps vs running a 180ish temp to compare the difference in temp, not while driving just over a 20-30 minute time frameā¦ But that may never happenā¦ lol
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Checking everything.
Back flushing heater cores and engine block.
Only thing left is radiator and ghosts. (Iām doubting itās the radiator)
Freak, rare rust blockage in the engine block?
Iām gonna find this rascal dag nabbit!
One other tidbitā¦
I havenāt really seen any āflowā in the radiator once the thermostat opens.
I canāt recall in the past if I could but I expected to see the coolant somewhat moving from inlet side towards the other side when the cap was off and the engine was running and at operating temperature?
The only indication of flow is with the thermal camera image I posted above.
So while it looks like hot coolant is moving in the radiator, it doesnāt say how much (volume).
It would only take a very small flow of hot water to make the thermal camera respond.
Still want to check for exhaust gasses in the coolant as someone previously suggested.
Nothing I have tested or seen has suggested that type of head gasket issue so far.
My gm scenario is I get engine hot/ac off message but thermostat is failed and stuck open. Just a trick gm does on some cars. Scan tool showed 160f and dash said motor was hot. You are using scan tool to display real temp?
Mine or my sons now, is the same colorā¦ lol
BTW, you may already know this by now but as easy as the front spark plugs are to get to from the top, do the rear ones from under the vehicle, from under they are easy, from up top they are a PITA!!! Ask me how I know, I didnāt look the 1st time and I went from up top, then after done crawled under to do something else and looked up saw all the room needed to replace them from under the vanā¦ lol
Two Scan tools, thermal camera, ELM327 AND laser thermometer.
XTool is nothing more than an expensive OBDC reader on these pre 2003 vehicles.
My $10 ELM327 is more helpful.
Donāt bother with XTool if your vehicle is 2003 or earlier is my advice.
I find it faster and easier just to remove the intake plenum.
Then the rear plugs are as easy to change as the front 3.
Only takes 20 minutes and lets you check a bunch of other stuff at the same time.
Saves time imo.
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Still trying to make sure thereās no hidden obstructions anywhere before I start putting it all back together.
Butā¦in case the Ghost wonāt let my engine cool down I am wonderingā¦
At another forum, the moderator dismissed completely my question about whether or not a clogged catalytic converter could cause engine overheating. I read at some places that overheating was a symptom of a clogged CAT. He said forget about it. He also closed my thread without any real help saying he had given me all the information necessary and I was going in circles to doubt his advice.
So what say you?
It seems that an engine that cannot easily move itās hot exhaust gases out would have no choice but to overheat (and lose power). Could a clogged or even partially clogged CAT be the ghost?
Before you answer consider that my ODB2 report is reporting a failed emissions control system, including the catalyst.
If the overheating persists after all of this I plan to remove the upstream O2 sensor and drive it just to see what happens.
The engine has no power? I overlooked that detail in this thread. Instead of replacing the radiator you should be diagnosing the cause of power loss.
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You cat could be in need of replacement, but if cat is clogged enough to cause engine overheating, that would most likely would also cause very poor engine performance, poor acceleration, stalling, etc. Do you have trouble accelerating your DGC to freeway speeds on freeway on ramps? If so, removing the upstream sensor for a test is a reasonable plan I guess. Was there any other problem besides cat in the failed emissions test report mentioned above? If engine is running overly lean, that could cause both overheating and a failed emissions test.
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Yeah I donāt remember seeing that earlierā¦
My neighbor was chasing an issue with his Nissan Altima with limited power under full throttle. Suspected Cat so pulled O2 sensor and drove it. No change except the expected extra noise. Later, still chasing it down, he disconnected the pipe but left it hanging in front of the cat. More noise but no change. Later, he pulled the cat entirely and then noticed a huge difference in power. Even a disconnected pipe but still in close proximity was affecting exhaust flow enough with a plugged cat. Just be cautious of conclusions with the O2 sensor out of the pipe is my suggestionā¦
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Is replacing cat on 24 yr old dodge an issue? Rust wise? How many cats does a 99 dodge v6 have?
Most exhaust shops should have an exhaust back pressure tester, or you can buy one and do it yourselfā¦
Lot of You Tube videos on how to do itā¦
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