Is my temp gauge working correctly? - Team Camaro Tech
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post #1 of 17 (permalink) Old Aug 14th, 11, 09:13 PM Thread Starter
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Jason
 
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Is my temp gauge working correctly?

I have a 396 4spd '67. When I got the car the temp gauge didn't work. I replaced the sender and then the gauge to get it to work. Now when I run the car for 10 miles or so on the highway the temp gauge creeps up towards the 'H' on the gauge. Around town it stays in the middle - straight up. I checked the timing and was pretty advanced (50 degrees total!) I set that to 36 degrees total. no help. bottom radiator hose seemed spongy and replaced that with a firm one. no help. checked thermostat (160) and opens at 160 in a pan of water as it should. richened the idle circuit on carb. no help. radiator is a three core from what I can tell by looking through the filler neck. am running a shroud and 7 blade stock fan with clutch. I finally took the sender out and wired it in a can of water and heated to see what the temps were. Looks the needle points to the right of the gauge at the H at only about 210 degrees. straight up in the middle is about 190. So on the highway am running about 205. Questions are: 1) Is this an OK temp to run at? 2)Does this seem like normal gauge function? It seems like a narrow range of operation and it bugs me to always see that needle creeping over toward the hot end of the gauge. thanks for any ideas!
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post #2 of 17 (permalink) Old Aug 14th, 11, 09:36 PM
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Re: Is my temp gauge working correctly?

Quote:
1) Is this an OK temp to run at?
just under "h" about 210....? yes
looks like u have done a lot of searching for info before posting....sweet

u should have a 180 deg thermostat...orginal factory I believe was a 190.
Even so the engine should, cooling all on good condition, no more than about 5 above the thermostat rating.

Straight up and down on my gauge is about 190.
It is genweral rule of thumb manufactures have the correct temp mid range of a gauge

Quote:
I checked the timing and was pretty advanced (50 degrees total!) I set that to 36 degrees total.
Just checking...u disconnected the vac advance, took the rpms up till advance did not go higher, and then set at 36 deg? u can set a little lower around 34 due to our modern fuel mix.

The only things really left to check is blocked cores in the radiator.
Cold morning fire up and feel how the radiator warms up with rpms up around 1200....enough for the water to flow thru and hit the other side of the header tank.
It show warn even...if not indicates some bloocked cores
Another indication is remove the stop ****, with a bit of mig wire see if u can hook crap out...like bits of gasket, broken bottom hose interal spring etc

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post #3 of 17 (permalink) Old Aug 15th, 11, 03:22 PM Thread Starter
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Jason
 
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Re: Is my temp gauge working correctly?

Thanks Steptoe - as far as timing the car had an MSD ignition and distributor on it without vacuum advance when i bought it, so I didn't disconnect anything, I just ran the engine up until the timing was all in and then set it to 36 degrees. hope that is the right way to do it. I will try the warm up test to see if the radiator warms evenly. Can a blocked heater core cause higher operating temps and if so any way to check the heater core without pulling it?

The car has headers and a bigger cam - unfortunately i don't know the specs but overall is not that heavily modified and seems to me it ought to be more stable in terms of operating temp. If you run it hard from a stop up to 60 or 70 it sends the temp gauge over to the right pretty quickly. Maybe thats normal -this is my first big block chevy. thanks for the advice...
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post #4 of 17 (permalink) Old Aug 15th, 11, 10:04 PM
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Re: Is my temp gauge working correctly?

Quote:
I just ran the engine up until the timing was all in and then set it to 36 degrees. hope that is the right way to do it
Yes....then adjust the springs so its all in about 3000 /3200 rpms
And adjust the amount of cent degs to maintian the 34 all in but have about 8 to 10 degs intial.
8 to 10 degs intial is not enough to idle...
Thats where the VA comes in.....
u establish a good idle advance....somewhere between 16 and 20 degs (depends on you engine) if ithe idle advance is established as say 18 degs, and the intial is 8 degs, then 10 degs in the VA all in at the vac when idling at the intial....
So easy low load on the starter with the low intial, fires, the VA comes in and idles at about your 18 degs

Quote:
Can a blocked heater core cause higher operating temps and if so any way to check the heater core without pulling it?
Yeah...if everything else in the cooling is good, fan clutch, pump hoses cap etc....it will be radiaror cores.
I dont get the logic of 99% of guys who rebuils or put a new engine in.....they replace the oil pump and a whole lot of other stuff, but dont pull the header tanks on the radiator, manually clean the cores.
The stock radiators and pump etc are WAY WAY over built...hence the take a lot of abuse, neglete for yrs on end before giving trouble.....And that trouble is usually not long after and engine rebuild...which by coincidence, little bits of gasket sealer fall off, eventually get into cores that are partly blocked, and with those blocking off plus the ones already blocked /partly blocked, the radiator stops doing its job.

Fortunatly in NZ we still have old school tradesmen who rebuild raditors ....withing a 4 mile radius I know 3, awhere of another 3....Spend a biy of time with these guys and they will show one this stuff....including my own raditors lol

Damn near all engine rebuilders in NZ and the sale of a new engine, a fully serviced or new radiator is a requirement of the garantee.
Thats how important this is.

Quote:
If you run it hard from a stop up to 60 or 70 it sends the temp gauge over to the right pretty quickly.
NoW THAT is a worry, even a radsitor that is a bit blocked, it should not heat that fast.
2 things cause that
a stuff radiator cap or to low press rating (make sure u have a 15lb cap)
And
Blown head gasket
Forget the bubbles in radiator ...its not relable
Head down to the local workshop, they can test the cooling system for hydrocarbons (HC) it takes about 3 to 5 mins..including getting the tool off the rack, setting up, running the engine, clean and put away....most workshops do this in NZ as a fee check.

Even a 3 core in good condition is fine on a BB....that is howover built GM made there cooling systems.

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post #5 of 17 (permalink) Old Aug 16th, 11, 09:08 PM Thread Starter
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Jason
 
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Re: Is my temp gauge working correctly?

thanks again for all the advice... I checked compression tonight to rule out a head gasket issue. lowest compression was 160, highest was 171 so hopefully i am correct in assuming that the head gasket is ok. will take the radiator cap down to get it tested tomorrow - it says 15lb on it but who knows if its ok...

as an aside - i'm not sure a vacuum advance would even work on the car as the manifold vacuum only measures about 5mmHg at idle. have sprayed carb cleaner looking for vacuum leaks and not found any and always assumed this was due to larger cam. only possibility i've found is that when the brake is depressed sometimes the idle goes up about 200rpm so i have wondered if there is a vac leak in the break booster.

will keep you posted on the rad cap test. thanks much!
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post #6 of 17 (permalink) Old Aug 17th, 11, 06:58 PM
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Re: Is my temp gauge working correctly?

Quote:
I checked compression tonight to rule out a head gasket issue
Again not reliable..that picks up obvious leaks, which generally are big enough to slowly increase water temp to eventuslly the radiator boils...or hits the red line idiot light 235 degs.
A slight leak does more like u describe...gets worse over time.
Quote:
will take the radiator cap down to get it tested tomorrow - it says 15lb
By the time one messes around checking it....just buy a new one...keep the old one as an emergence spare if turns out its not the cap.
Hence why I did not suggest doing a compression and simply get the radiator checked for HC....also damn sight easier than pulling plugs and stuff.

Quote:
i'm not sure a vacuum advance would even work on the car as the manifold vacuum only measures about 5mmHg at idle
And that is because of the issues with pre and post ported/ manifold dizzies as I describe above....Thats like dropping 14x 175 x 60 tyres on your rims...the car moves but falls ove on cnrs and wobbles down the road.

Quote:
i've found is that when the brake is depressed sometimes the idle goes up about 200rpm so i have wondered if there is a vac leak in the break booster
most common area there is the seal behind the MC......get a $20 hand mechanics vac pump....another very usefull tool, espec when tuning in VA on the dizzy....and doing stuff like sucking brake fluid out of a MC when the end easl on the MC leaks back into the booster, and containers for bleeding brakes etc.

Quote:
have sprayed carb cleaner looking for vacuum leaks
A $10 lpg pen torch is far easier to use... and manually check butterfly wear...hollies do have a little play, other carbs no play...and check at different throttle positions.

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post #7 of 17 (permalink) Old Aug 18th, 11, 07:41 PM Thread Starter
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Re: Is my temp gauge working correctly?

thanks again for all your time and input steptoe, as you suggested i bought a new 16 lb radiator cap and ran the car pretty hard - seemed to improve things with the needle not getting quite so far over to the right. then again, it has cooled off here some in the last week so not sure if that is really what helped. Still gets up to 200-205 with a hard run. was in the 90's everday, now in the 70's. Hopefully it helped.

I will try to find a place that can do the hydrocarbon test as well.

I tried warming the car up as I ran my hand over the radiator, and it may be my imagination but it did seem to warm up a little slower in the middle of the radiator than at the top and bottom. Have located a shop that will drop the header tanks and rod out the cores but is 70 miles away so will have to wait until I can get it over there. They also mentioned that they could do an infrared test to see if it heats unevenly but am thinking if I drive the radiator all the way over there I'll just have them rod it out no matter what??
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post #8 of 17 (permalink) Old Aug 18th, 11, 08:30 PM
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Re: Is my temp gauge working correctly?

Quote:
Still gets up to 200-205 with a hard run. was in the 90's everday, now in the 70's
As I and others have mentioned many times, the GM factory system is way over built...ambent temp difference (weather) maybe 5 deg between a frosty morning and a 35 deg summer afternoon...and the difference will be lowerr not hotter
And loading...hard out 110 120 mph for 5 or 10 mins 5 deg...or up a winding mountain, tyres tearing at the road, 5 or 10 mins...maybe 10 deg over thermostat rating, and that is mostlikely because of altitude.

Quote:
my imagination but it did seem to warm up a little slower in the middle of the radiator than at the top and bottom.
yep that "imagination" describes exactly what what u are looking for...then sortly after the "is it isnt it" everything is the same temp ...you are 'on to it'
Quote:
They also mentioned that they could do an infrared test to see if it heats unevenly but am thinking if I drive the radiator all the way over there I'll just have them rod it out no matter what??
yep you are on to it again m8...cant believe a quailfied mechanic would even suggest something like that, unless they ask to keep the car over night...or drain and fill with chilled water.
Do the mechanics (tradesmen) over their have to do a 5 yr apprentice ship to meet national standards? or just dudes who get a bit of in house training?
Quote:
I will try to find a place that can do the hydrocarbon test as well.
Do a google see how much a unit is worth over there....
And the fluid in the tester is reusable...cant rem which way it changes off hand, but it works like this
the rubber bug jamed in the radiator, engine fired up, the rubber ball when squeezed sucks air out of the radiator thru the indicator fliud...3 or 4 sucks (if +ve) changes the colour from blue to green...
Thats it...pull the bung out, suck fresh air thru the indiactor fliud and goes back to the right colour...
The real expensive units comes with a pressure tester.

I have mentioned these tester several times here over the yrs, and cant believe how hard it is for u guys over there t find a workshop that has one....even most tin potty little workshops in NZ have them...I have one....its the 1st thing done when a car comes in ...well 2nd after checking water level...running hot.

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post #9 of 17 (permalink) Old Sep 3rd, 11, 09:06 AM Thread Starter
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Jason
 
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Re: Is my temp gauge working correctly?

An update on my cooling problems. After calling all 11 shops in town I found one out of the eleven that had the hydrocarbon tester steptoe recommended. They did the test for me and it showed no signs of a combustion leak, radiator was negative for hydrocarbons. They didn't even charge me for it - said getting a look at the car up close was good enough!

So I guess the next step will be pulling the radiator and having it rodded out. Hope to get time to do that in the next few weeks and will post results. thanks for all the help, steptoe!
jason
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post #10 of 17 (permalink) Old Sep 3rd, 11, 02:20 PM
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Re: Is my temp gauge working correctly?

Quote:
After calling all 11 shops in town I found one out of the eleven that had the hydrocarbon tester steptoe recommended. They did the test for me and it showed no signs of a combustion leak, radiator was negative for hydrocarbons. They didn't even charge me for it - said getting a look at the car up close was good enough!
Its hard for me as a Kiwi down under to accept u had to go to 11 shops...I dont disbelieve, I just find it incredable....the no charging is cool thu.
Did u ask them what they thought?

Quote:
So I guess the next step will be pulling the radiator and having it rodded out
Cost the job out as against buying a new radiator...
Chrges I think would be very different there than in NZ...it seems u guys dont have many radiator shops either....Get headers pulled, manually cleaned, tested, side struts re set, is about $NZ75 (about $US 50) and a same day turn around in most cases.

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post #11 of 17 (permalink) Old Sep 7th, 11, 06:46 PM Thread Starter
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Re: Is my temp gauge working correctly?

So I finally got the car to the radiator shop today and was a bit disapointed. The guy at the shop who has been in the radiator business over 50 years took one look at the radiator and said it was not the oem radiator by looking at the flanges, also only 3 row, and should have 4 rows for a 396. He said he could drop the tanks and rod it out but I may still run hot. Told me by the time he did all that it would cost almost as much as just buying a nice, thicker aluminum radiator and didn't think it would be wise to invest that time in an aftermarket radiator. I had wanted to keep the engine bay looking close to stock but to get a correct looking 396 4 core brass/copper radiator is significantly more than the aluminum one and probably not as good? Offered to sell me the aluminum radiator for 320$ (northern radiator brand) which is 5/8 inch thicker than whats in it (1&7/8 inch). I am thinking that may be the way to go... any suggestions?
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post #12 of 17 (permalink) Old Sep 7th, 11, 08:57 PM
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Re: Is my temp gauge working correctly?

Have u had the headers pulled and cores manually cleaned?
The 3 core is way over built and in good nick, will handle big block nps...but not with cores blocked.
As to orginal brass or Aluminim...well the reality is the difference is like comparing 2 reputable brands of oil....but each promote their own propagana....yet brass/copper is still the best conductor, and painted black improves cooling a hugely significant amount,

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post #13 of 17 (permalink) Old Sep 7th, 11, 09:32 PM Thread Starter
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Re: Is my temp gauge working correctly?

I didn't do anything as the guy at the shop recommended that I just buy a new radiator. Since he makes a lot less money off the new radiator than off the shop hours involved in reworking the old radiator it seems like an honest opinion rather than trying to make a buck. It would cost me about the same to have them drop the tanks on the old 3 core rad and clean out the core as it would to buy the aluminum rad. What should I do?
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post #14 of 17 (permalink) Old Sep 8th, 11, 04:01 AM
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Re: Is my temp gauge working correctly?

Have you looked at your jetting? Carb cleaner doesn't work nearly as well as start fluid to check for vacuum leaks - I'd try that next, just stay away from the distributor. You didn't mention it but I assume you a fan shroud, and when you look in the raditor you have good flow with the thermostat open indicating the water pump is in good shape?

If you decide to go the radiator route, and want to maintain a factory look in the engine compartment - might want to check out the alumitech radiators. They are very nice and look very much like the OEMs. For a concourse restoration they also make some excellent Harrison replicas with the correct embossing and tags etc. Either will be more expensive than the radiator the shop has offered you but are also well known solutions that perform excellently.

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post #15 of 17 (permalink) Old Sep 8th, 11, 01:58 PM
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Re: Is my temp gauge working correctly?

Pulling cores and manual clean in NZ is about $NZ 75 thats about $US 50...same day or 24 hr turn around.

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