[RESOLVED] Would High Coolant Temp cause knock?

[mattdev]

Coolant temp is running hot (due to thermostat, which is going to be changed) about 210-230max. Last WOT 3rd gear pull I had 7* timing, while my a/f ratio was under 11:1.

Running 22psi w/ 93 octane should be pretty simple. What makes me ask, is my underhood temps are extremely high (I'm guessing due to my high coolant/engine temps), would this cause me to knock/pull timing due to the all around high temps?


Thanks!!

 

[1992awdlaser]

It will make it easier for the car to knock. The heat in the cooling system also means the block and head are going to be hotter which will cause the extra heat to go into the cylinders/combustion chamber. That will make it easier for the car to knock. I think there is something else wrong though if it's reading 7 counts of knock.

 

[iluvmy4g63]

Coolant temp is running hot (due to thermostat, which is going to be changed) about 210-230max. Last WOT 3rd gear pull I had 7* timing, while my a/f ratio was under 11:1.

Running 22psi w/ 93 octane should be pretty simple. What makes me ask, is my underhood temps are extremely high (I'm guessing due to my high coolant/engine temps), would this cause me to knock/pull timing due to the all around high temps?


Thanks!!

i serously dout it would cause knock. but it might cause head gasket problems. did you start getting knock when the thermostat went up?

 

[mattdev]

Well, it's not 7 counts of knock, I'm only getting 7* of timing advance, should be near 20*. (damn 2g ecu's w/ no know sum).

And that's the logic I had, when the coolant temp is up, the head and block are hotter than normal, making it easier to detonate. My reasoning is a combination of high intake temps and engine temps would cause excessive knock.

What are some other reasons for all the knock? I am checking into exhaust leaks before the wide-band, and some boost leaks. Is rich knock possible from running well under 11:1 a/f ratio?

 

[throwedgsx]

how "well under" 11.0/1 are you?

 

[mattdev]

anywhere from 10.2:1 to 10.6:1

 

[snowborder714]

2g Coolant Points:

Enter ECU Learn Mode :: 170F (77C)
Coolant Fan ON :: 200F (93C)
Pull 1 degree timing :: 206F (97C)
Pull 2 degree timing :: 224F (107C)
Enter Open Loop Mode :: 228F (109C)
Default Coolant CEL :: 235F (113C)
A/C Override :: 240F (115C)

High intake temps will also pull timing.

 

[mattdev]

Very helpful, my coolant temps will level out at about 103 Celsius and after pulls will be at about 107-109, that answers a lot of my timing questions.

I will be changing to a 180* thermostat, considering I have a Duralast thermostat (I believe over 190*)

 

[mattdev]

All right, I still have some issues after t-stat swap.

I installed a stant 180* t-stat, which drastically lowered the temps (no duralast parts for me) Instead of leveling out at 220*F all the time, I occasionally spike to 220*F and will level at about 206-213*F. Must be the water pump, correct?

Also, I made a CAI, which brought my timing up to about 12* advance. Better, but still not Good.

I have some pretty extreme underhood temps. Does my relatively high coolant temp make for this?

And just to clarify... Radiator fans are supposed to suck air IN from OUTSIDE, correct? Not pull air OUT of the bay.

 

[->PrOjEcTGS<-]

All right, I still have some issues after t-stat swap.

I installed a stant 180* t-stat, which drastically lowered the temps (no duralast parts for me) Instead of leveling out at 220*F all the time, I occasionally spike to 220*F and will level at about 206-213*F. Must be the water pump, correct?

Also, I made a CAI, which brought my timing up to about 12* advance. Better, but still not Good.

I have some pretty extreme underhood temps. Does my relatively high coolant temp make for this?

And just to clarify... Radiator fans are supposed to suck air IN from OUTSIDE, correct? Not pull air OUT of the bay.

Might want to do a leak down test to check for a blown head gasket. That can cause an overheating situation.

Yes, stock fans are "pullers" which will draw are in through the radiator from the front of the car.

 

[1992awdlaser]

That is how the stock fans are set up, yes. Is this problem at idle, cruise, or both? What is your coolant/water mix ratio?

 

[mattdev]

Ok, I have one 14" Puller, and a 12" Pusher, they aren't re-wired to a switch or to ign. switch. Do the fans stay on during cruise?

It's mostly at cruising, the temp will come down to about 193 after a few minutes of idle with fans blowing.

Leakdown test is on it's way... The only thing that leads me to believe it isn't the headgasket is I show no other signs of it being blown. I don't burn anything, oil and coolant are clean, I don't leak anything, etc. And after 3rd gear pulls, WOT runs, etc. the temp actually goes down, and comes back up to the same temp. It doesn't go shooting sky high.

Is water pump still a valid option?

 

[1992awdlaser]

During cruise is most likely because of lack of airflow to the radiator. No the fans don't run all the time during cruise.

 

[mattdev]

Well, I'll just have to "coax" those fans into blowing won't I?! I'll keep you guys posted.
Thanks!

 

[1992awdlaser]

The easiest way to do it is take out the fan relay.Connect a wire to two of the terminals. Not sure which ones they are but they will be diagonal from each other.

Edit: This works on a 1G. Not sure about the 2G since the fans are controlled by the ecu. Just try it with the igniton on and the car not running. If it will work they will turn on when the wire is contacting the correct terminals.

 

[mattdev]

All right, the fan switch re-wire seemed to drastically drop temps. (that and getting all the air out of my system...). I can now cruise highway at 203-206*F, when its about 90* out. Low speed is about 199-203*F. And Idle is 193-199*F.

Look pretty decent?

 

[KGB Pilot125]

I love when you see the brainstorming and feedback solve a problem. This situation reminds me of when I had my twin turbo v8 we went through a ton of stuff trying to figure out a overheating condition that occured mostly at cruise, we tried t-stats, those washer looking things that take the place of the t stat, ducting, sprayers, different caps, and overflow tanks all sorts of stuff then one day I was standing in front of the truck with a friend and the fans kicked on and it started blowing air out of of the engine bay! DOH somehow we hooked the fan up backwards and it was blowing air back out of the bay and causing it to over heat at speed.

 

[jrohner]

I just turn the AC on when I want to cool my engine down, because then the fan is on whether the engine is running or not.