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high flow thermastat.

rjfguitar

rjfguitar

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So I have been plagued with overheating problems since I dropped in the 406 and still don't have it figured out....Some may remember me having problems with my motor overheating within a minute or 2 with the heater core hoses plumbed in to the core itself...well I think my problems are related and it is a flow issue. For some reason with the heater hoses connected to the heater core and not looped together it is like the cooling system "locks" up and won't flow and the temp goes strait up within seconds.

I put a brand new 3 core in when I put the motor in and when i started having problems with it getting hot in town(no heater connected) figured it was just a problem with needing a 4 core and the 3 core just not cooling enough. Well I bought a brand new 4 core big tank rad. and it almost seems worse now when the weather gets warmer, it wants to hang around 200-210 in 75 degree weather!!! /forums/images/graemlins/yikes.gif Oh and I have a 180 stat. So I have pulled off the return line to the rad. and I am getting a decent flow of return but I am wondering if I am not getting ENOUGH return through the stock size stat. Either that or there is something wrong with my brand new summit hi perf. water pump. I know I am getting enough air across the radiator because I can get on the highway at 70 and it will hang at about 205 or so and not come down, 70mpg should provide all the air flow it needs right? How much does the rad. cap effect flow?

Has anyone had problems with not getting enough flow through the motor before? What does a water pump do if it is going out but the bearing feels nice and tight? Do they lose pumping ability? The motor only has about 10K on it including the pump.

I know it's a 400 and everything but geeze... you would think a brand new 4 core, new HD fan clutch, and hi performance water pump would keep it cool in 75 degree weather. /forums/images/graemlins/doah.gif
 
i know that this is not much help but my 97 sub with a 454 in runs at 210 and thats in san dog all year . but look to see if you have the right pump if it is not a reverse flow and did you use your old block or did you put the intake mainfold gaskets on right or are you running non 400 heads becuse of the steam holes
 
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it wants to hang around 200-210 in 75 degree weather!!!

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That's not a bad temperature. As long as it doesn't go much higher than 210, I wouldn't worry about it. That's a good temperature for efficient combustion.

Try completely pulling the t-stat and seeing what temps it wants to run at. It will take longer to warm up, but I would guess it would stay at or below 180.
 
I run a 180 degree stat and my stock gauge says I run a hair under 210. (no matter what the weather...-10 or 100)And all of my cooling parts are new as well.
Being between 200-210 is good in my book.
Blake
 
Least you dont have a 6.2 that runs around 215...all the time, 40 degree weather or whatever it is out /forums/images/graemlins/crazy.gif I think im gonna go all out new system this summer if a flush and thermostat doesnt work
 
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I run a 180 degree stat and my stock gauge says I run a hair under 210. (no matter what the weather...-10 or 100)And all of my cooling parts are new as well.
Being between 200-210 is good in my book.
Blake

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I also run a 185 t-stat, my truck stays right around 180-190 Never over 190.
 
I wouldn't flat out pull the t-stat out completely, it will definately overheat during summer months (experienced) i actually would go ahead and replace the t-stat with the high flow unit and see if that helps out. You may have gotten a "somewhat" defective t-stat, i have heard of this before from time to time. may not be opening up early enough or even completely. I have used those high flow t-stats before and i liked them, very reliable, kept things at normal operating temps. Give it a try and see what it does.
Also may just for peace of mind, check out the parts number of the water pump they sold you, just to be absolutely sure they didn't sell you a reverse flow pump, i don't think you have the reverse setup/serpentine on thing in '85 right?
 
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plagued with overheating problems since I dropped in the 406 and still don't have it figured out

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So its since day one. I don't know the motors background so tell me. Did the heads have steam holes? Is your timing off? Temp can and will change with the timing being off a bit. Seen this on everything from 350's , to jeep sixes , to datsun lowrider trucks. /forums/images/graemlins/k5.gif
 
Experience has shown ME that not having the 'stat=cold engine.

I know thats not always the case, others have done just as I have and had the exact opposite result (like you say) so it seems to be a toss up.

Mine was in a car with a small V8, so it *should* have been able to warm up, but from the temperature gauge (which did work fine with a new 'stat) it never got over about 100*, and indeed, I could pop the radiator cap, no pressure, and stick my finger in the coolant after running it hard.

It's worth a try IMO if you can pull the 'stat out easily.

I hesitate to blame the pump, but not all are created equally. The impeller is pressed onto the shaft, so unless it's slipping (and that would probably have the shaft come out of the pump!) there really isn't a way they can fail and for it to lose its pumping ability. But there are pumps with more vanes, less vanes, larger impellers, smaller impellers, and anti-cavitation plates. Since yours has done it since day one, it COULD be pump, but 'stat is so easy to check (usually) it would be the first thing *I* would try...if it starts overheating fast, turn it off and replace.

I have a 403 olds that is bored .060" over (supposedly beyond safe limits, siamesed cylinders) and I haven't been able to completely lick it's overheating issue either. And in my climate, that is a problem, since it shouldn't be taxed much. Really only starts to climb in traffic, and DOES equalize, but higher than I like.

IMO if everything is working RIGHT, temp won't fluctuate hardly at all no matter you are doing with it, but largeer motors certainly make it more difficult to accomplish. The 350 that was in my truck never wavered in engine temp, unless I pulled the fan off and drove around town, (did that just to test how effective the fan really was) in which case stoplights were interesting, but cruising over 25 with little load was no problem whatsoever, and that was with an old 2 core.

Seems that results vary widely with cooling systems, tweaking and modifying to find the right combo seems to be the only answer.
 
The experiences i have had with the removal of the t-stat was too cold in cold weather temps, and overheating in hot weather temps, which we do get alot of here in Arizona. So basically i am forced to run a t-stat, especially with the TBI anyway.
 
Well my overheating probs have been a progressive thing. When I put the motor in last April I had my heater core hoses plumbed in and it ran plenty cool(185 or so at the stat temp). Then I got into the summer months, fixed my A/C, and it would run a little warmer(around 200 with the A/C and 3 core rad.) Now from driving it around in 75 degree weather and it running 210 I can tell it won't stay cool in 90+ weather this year...so obviously it's getting worse. IMHO 210 is OK for a stock motor but with a built motor it should stay cooler. My 406 will start pinging with decent throttle when it's above 200 degrees.

As for the stat, it's a napa stat and I have had 2 different ones in it with identical results, I have ruled out a defective stat.

So yesterday morning I noticed a little bit of coolant seeping between the block and head above the starter in #8 cylinder, I have had problems with oil buildup on #8 plug also. Did I mention I am burning oil with a 10K motor? /forums/images/graemlins/rolleyes.gif

I talked to my girlfriend's dad this morning that helped me build the motor and we are thinking the head gasket may have been defective or it slightly shifted on us during install. He says the headgasket would explain the continual worse overheating probs, oil burning, and #8 cylinder oil/deposite buildup.

If it is the headgasket....the motor is coming out /forums/images/graemlins/angryfire.gif and I am going to rebuild with with a 4" crank, AFR195cc Alum heads, forged pistons and rods, and I might run it on propane so that way I am smog exempt for alternative fuel. /forums/images/graemlins/laugh.gif Oh well, here goes another $3k probably. /forums/images/graemlins/whistling.gif

So does the headgasket sound like the culprit guys?
 
Just an FYI:

My 454 which has a 4-core Modine, Edelbrock WP, 180* stat and NO fan shroud will get to about 210* on the hottest of days here in Colorado it usually sits around 190*... I have also found with some engines, there is such a thing as TOO much flow....if the coolant isn't able to spend enough time in the radiator, it will run MUCH warmer...I have seen cases where running a hi-perf WP nd NO t-stat will cause temps to rise up to 220*.. throw a stock WP on there and a stat and it comes back to about 195*... This is more ture for higher rpm applications when the water pump is moving A LOT of water through the rad...

Chris
 
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throw a stock WP on there and a stat and it comes back to about 195*...
Chris

[/ QUOTE ]I have a stat in it right now and my water pump only flows like 30% more than a stock one anyway. /forums/images/graemlins/dunno.gif

When you say the hottest of hot days...How hot? Your 454 should be a harder motor to keep cool than my 400 right? Obviously 75 degrees in colorado isn't very hot so I'm guessing it would be 190 like you said on a day like that?

I am really leaning towards the headgasket. /forums/images/graemlins/thinking.gif
 
1st thing I would do is make sure the temp gage is correct. Then I would pull the t-stat and see what happens. You will have spend no $$$ and might find the problem there.

Does it cool down if you turn on the heater full blast?
Do you have the heater core plumbed up?

If you just run a loop to bypass the heater core (and even if you don't) you will have flow going thru the heater core that could/should go thru the rad. There are 2 ways to get around this...
1) Tap out the heater hose fitting on the pump and put a plug in it...then drill a 1/8" hole in the plug and reassemble it. You will now have restricted the flow to the heater core and more will get to the rad where it can cool the motor.
2) Get a heater switch from a europian car (I think they used them on 1st gen K5's as well) and hook it up so it will block off the heatercore when the AC is on (or when the heater is off if you don't have AC). If you do this you will have to drill at least 1 or 2 1/8" holes in the t-stat to keep the water moving when it is warming up.

I have seen a pump fail internally and have no sign outside...about half of the fins had rusted and broken off of the impeller /forums/images/graemlins/yikes.gif...but that was a stock pump with 160k miles on it.

If you arn't boiling the motor over the rad cap has nothing to do with your problem.

FWIW I have never seen a motor run anything but too cold without a t-stat unless the rad was way too small or all cloged up.
 
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So yesterday morning I noticed a little bit of coolant seeping between the block and head above the starter in #8 cylinder, I have had problems with oil buildup on #8 plug also. Did I mention I am burning oil with a 10K motor? /forums/images/graemlins/rolleyes.gif


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I think you answered your own question, coolant seeping is a definate bad thing, What does your oil look like? My $.02 is to diagnose it don't just throw more parts at it... Your next step should be a presure check on the cooling system, I'd leave the #8 plug out when you do this because you may have coolant in it when you are done.... odds are you will hear it leaking by or in #8 cylinder, you could also do a compression check, I like the pressure check because it is quiet and you can often hear the leak.

(edit) Did you use head studs when you built the motor? If so they can (and usually do) seep...
 
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FWIW I have never seen a motor run anything but too cold without a t-stat unless the rad was way too small or all cloged up.

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You haven't been in Arizona at all then have you, /forums/images/graemlins/thinking.gif as i stated before, i believe it has alot to to with the ambient temperatures. Around Phoenix in the middle of summer, when it's runnin 115-120 degrees, /forums/images/graemlins/yikes.gif if you run without a t-stat, you can just about be gauranteed to overheat, unless maybe you have a factory fan with the clutch removed for direct drive. /forums/images/graemlins/thinking.gif

Anyhoo, hope ya get it fixed, as was mentioned, the water coming out from between the head is not a good sign and could definately cause it to overheat, and it WILL only get worse, i wouls suggest you just you just remove that side, inspect everything, make sure it's in good working order, and reinstall it with a new head gasket. Would definately save you alot of money /forums/images/graemlins/dunno.gif
 
Triaged,
I have the heater hoses looped together so there is no water going to the core itself. I have the hose connected at the intake, not the water pump. I have always seen SBC at the intake and BBC at the pump. /forums/images/graemlins/dunno.gif

Everyone,
I agree that it shouldn't be the water pump. My dad was telling me about problems that he used to have with the older detroit motors in the trucks...they would act very funny with a headgasket problem. Overheating for no reason, temp goes crazy with the heater on, burning oil...

I have checked the oila and water, no signs of mixed fluids thank god! My guess is that it is just slightly burnt through the headgasket someplace allowing a little combustion to come in contact with the coolant. /forums/images/graemlins/thinking.gif

I have replaced everything in the cooling system besides my water pump so I am 90% sure it's the headgasket. /forums/images/graemlins/1zhelp.gif /forums/images/graemlins/frown.gif

Well I can't touch it until late May but when I get the time I will pull off the passenger fender and remove the head. Apon inspection of the pistons is when I will decide if I pull it, start all over again, and make it a 434ci...( I let the motor run a little lean for a while) Or depending on my cash situation I might just leave the bottom end alone, bolt on a set of 195cc AFR alum. heads, and (what the hell /forums/images/graemlins/whistling.gif) Edel. multi point FI. /forums/images/graemlins/woot.gif /forums/images/graemlins/peace.gif /forums/images/graemlins/doah.gif

What do you guys think?
 
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