After about 150 miles of trouble free driving in the last couple of weeks, the Laurentian started to run hot last night. I drove about 20 miles without a problem and while waiting at a drive thru for ice cream for my son and I, the gauge climed from 1/2 to 3/4. I figured once I got moving it would calm down. Nope-it climbed even higher! When I got home I popped the hood and checked for any leaks etc-none. I checked the oil (and burnt myself on the dipstick handle!) and the level was fine. I don't get it. Headgasket problem? I'm taking the car to a buddy who has some sort of gizmo that tests for combustion gases in coolant. If it were a rad or water pump issue, I'd figure this would have cropped up right away. I doubt it's the t-stat as the gauge was at 1/2 for quite a while before it started to run hot.
Is the cap for sure good and holding pressure?. And the rad hoses have the inside wire thing and aren't kinked?. The waterpump is recent or known good...and turning the right direction, not a serp style pump?. No exhaust obstructions?. Is the rad decent, does it flow coolant well and there's no chance the passages are full of rad-stop goop is there?.
Since your car didn't cool down on the road, you'd think the added air would've cooled it if it was an airflow problem...fan/shroud/fan clutch/dirty fins etc?.
Pull the stat and see what temps it runs without it?.
When buddy sniff tests your coolant for hydrocarbons, if the reading is positive and all else fails, keep in mind you'll need to mag the heads as there could be more of a problem than a head gasket?.
Have you operated this engine in the car in past years without the problem or is it all new to you?. And by chance, it's not a SBC 400 is it?.
Good luck!.
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I like real cars best...especially the REAL real ones! ----------------------------------------------------------------
Hey Todd, not to make light of your concern but I say throw in a 10 ohm resistor on the line and drive the car. I was preocupied with my gauge before I changed it out to a more accurate one too. It bugs you to see it climbing I know but you don't see any steam...
Now that I put in a new factory trio the temp is ok but the oil pressure reads lower than the one I had before, about 30 psi driving around town vs. 40 psi before.
How accurate were these factory gauges anyway, and now that we are still using them 40 years later ?
The other night, that hot humid Monday night, 65 Camino and I came home from Thornhill Cruise In. When we stopped at home the El Camino started sprewing out coolant and the gauge said 210. That was a mystery.
It's the original 350. Just purchased last year. It ran at 3/4 until I put the tstat in and was behaving itself up until yesterday. Rad has been cleaned out, rad hoses appeared ok (both were very hot -no kinks etc). Fan is factory and there is a shroud. I'm going to a 454 possibly this winter if I can swing the $$ to do it (it's been an expensive year around here). I guess I'll just drive the damn thing and ignore the gauge. I guess that's why I finally got CAA and a cell phone! My buddy with the 427 small block is having the exact same problem. He finally pulled the stat and now runs without it.
You said you flushed the rad......did you flush the engine as well?If it runs fine for two weeks, then starts overheating.Something must be floating around to block your cooling system.Take your tstat off and stick it in boiling water and see if it opens.
If it runs fine for two weeks, then starts overheating.Something must be floating around to block your cooling system.
Correct me if I'm wrong Todd, BUT the car is not overheating, it's the darn US Bonneville gauge that has you spooked and I understand, so do as you say, ignore it or do as I say and wire a resistor into the line.
I didn't know there was a spot on the other head for a gauge. I thought the drivers side head and the intake were the only locations. I'll give that a try. Ray-I didn't spoof the gauge- I put the 180 t-stat in and it was running at 1/2 until last night. I went out tonight and it ran fine-1/2 again. Maybe I have a piece of crud in the block causing an intermittent obstruction?
Ray-I didn't spoof the gauge- I put the 180 t-stat in and it was running at 1/2 until last night. I went out tonight and it ran fine-1/2 again. Maybe I have a piece of crud in the block causing an intermittent obstruction?
That is good news. Maybe you just watch it for the next month then when the Big Block drops in you'll need another rad anyway. Ask Astro Jet about the rad, his factory 454 70 Laurentian is prone to overheating with the factory rad he has.
I didn't know there was a spot on the other head for a gauge. I thought the drivers side head and the intake were the only locations. I'll give that a try. Ray-I didn't spoof the gauge- I put the 180 t-stat in and it was running at 1/2 until last night. I went out tonight and it ran fine-1/2 again. Maybe I have a piece of crud in the block causing an intermittent obstruction?
Todd
If you have a spot between the #1 and #3 plug there should be a twin to it on the other side between #6 and #8 plug. I would try that.
I don't imagine that the mechanical and factory electric gauge won't agree but you should at least be able to tell where you truly are at.
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1966 Strato Chief 2 door, 427 4 speed, 45,000 original miles
1966 Grande Parisienne, 396 1 of 23 factory air cars
Hey Todd, guess the easiest way to check the the temp is to get it at operating temp and use a thermo gun and point it at the thermostat housing. Better yet, drive it till it acts up, pull over and then use the thermo gun and compare it to the guage!! What have you got on it for a fan? Hopefully not the 4 bladed boomerang version! I know my 2+2 Rag runs warm and that is a targetmaster 350 with efi and the old 4-blade. My 2+2 coupe with a 350 target and efi is fine with a 5 blade clutch fan. My '70 with the 454 with efi also has a 5 blade clutch fan and there is no problem there. Of course, I can use my GM Tech-1 scanner to moniter the temp of all 3 as neither one has guages. (Not yet, anyways!!!)The kicker with the '70 is that I am still using the original 6-cyl rad it came with and all 3 don't have shrouds!
i agree with carl, put a mechanical temp guage in and be sure what temp it is actually running at. i've seen rads that were 'flushed' still be a problem. have it recored. my belair has a thicker, recored 6 cyl rad w/out a shroud, fan clutch, no stat but a restrictor, it runs 170-180.
The fan is the stocker (heck, I figured if it worked when it was new...) The season is coming to an end so I'll likely leave things alone and make all the necessary changes when I get the 454. I better go out in the yard and shake the money tree in preparation for that swap!
Todd. Did you ever solve that "running hot again" problem. If you did great. If you didn't I had the same problem a couple years ago. After running for a whole season(and worried every minute)and spending about $2000.00 trying to fix it. I found the problem. Hope your's is solved. Leo
Todd. Did you ever solve that "running hot again" problem. If you did great. If you didn't I had the same problem a couple years ago. After running for a whole season(and worried every minute)and spending about $2000.00 trying to fix it. I found the problem. Hope your's is solved. Leo
Since you asked, I solved the high temp reading on my new expensive electric AUTO METER guage.. I bought a laser heat reader, and after driving all the way to Port Elgin (Pumpkin feast) and back with guage at 210-215 I stopped in Goderich, for food, and I left it running, and checked it with reader 188 so much for the guage I bought a mechanical one from Brad...thats my story headers read 500-750 degrees
sometimes if a clutch fan goes, the car will overheat. Headgasket or blown water pump theres a beautiful cream color for your oil, or the antifreeze will be milky.
To make a long story short, I went to 5 different shops and all of them said no problem I can fix that. 1) Replaced the t-stat and flushed the system. Insisted water wetter would help. 2) Replaced the 2 core rad with a 4 core rad and replaced the 4 blade fan with a 5 blade fan. 3) Replaced rad hoses looked good but a little soft and could be kinking up and new rad cap. and installed a factory shroud.The chrome after-market shroud was useless. 4) Replaced water pump to a high flow and replaced the t-stat(last guy had no clue) and replaced the fan to 6 blade.(last guy should have known better) 5) Sparky's Performance-Last hope checked for about 3 hours and could not figure out why it still heated up (as high as 220 after sitting idle for 10 minutes then would cool to 190 when running on the highway.) We had some engine work scheduled for the end of the season so he said he would take care of this at the same time. He found one water circulation port from the block to the head nearly plugged. The block port is about 2 in. square, but the hole had factory slag in it, never been cleaned,closing the port to about 1/2 " size hole for water flow. Now runs at 175 on the highway, and sits at an idle for 1/2 hour and goes up to 195 on the hottest days of summer. Glad it did NOT tape over the gage and forget it. Leo
