Question: Wow. . .never got that hot before!

[Bolisk]

Before I start, I will say that I know that the guages and sending units are always out of wack. . .so no need to explain that.

I've had my 1970 350/350 vette for a three seasons now. In those three seasons, the cars temp guage has never read hotter than 220. Now when I've checked this with an IR temp gun, the actual temp at the thermostat housing is ~ 190 degrees. The temp on the radiator return hose (about half way accross it's lengh, shows about 181 degrees.

However yesterday, it was 90 here in the chicago area. . .and for the first time the cars temp guage read just short of the red area (250) on the guage. I nursed the car home and checked the same to places. At the thermostat housing it read 256 and was climing about 1 degree a second as it sat there at idle. At the hose it was 196 and climbing about 1 degree a second. The housing climbed to 286, and the hose climbed to 214 before I shut the engine down.

The car never boiled over.

The radiator intake (radiator to the block) hose was about 146.

Last year, I replaced the water pump, and had the radiator re-cored with the correct coper core. Car runs Mobile1 High Milage 10w30, and I have checked to see that there is nothing blocking the radiator.

Temp would drop a bit when the car is over 40mph.

So I have a few questions. . .

1) I know that big blocks have over heating problems. . .but is overheating normal for small blocks as well?

2) What defined over heating? When the car boiles over, or whenever the car is hotter than a certain temp.

3) When does the temp become a potential problem for the engine. . .ie. cause damage?

4) Is there anything I can do to improve this. . .without adding electrice cooling fans to the front? Basically, keeping the car stock appearing is critical to me. I can't imagine these small blocks had over heating problems on a regualr basis when new. . .any ideas as to the potential problem?

Regards,
JonR

 

[74bigblock]

Assuming there is nothing mechanically wrong...

If Automatic, put car in Neutral when at a stop (allows the fan to run at higher idle speed.

Try "Water Wetter" in your coolant, you can pick up at any local Autozone, O'rielly's, etc.

 

[Toms007]

Are you sure that the thermostat is working properly? If it is 286 at the housing (assuming thermostat housing) and 146 at the intake side of the radiator, seems that there is some sort of blockage there !? I'd check it all again and make sure there is nothing blocking a hose, thermo, radiator, etc,

 

[Bronze85]

Also if applicable, check the fan clutch for proper rotational resistance.

 

[Bolisk]

I'll check for blockage. . .

Also, what is the procedure for "burping" the cooling system?

 

[Bolisk]

as far as thermostats are concerned. . .

I think the 180 degree mr. gasket thermostat that I installed a year ago is supposed to fail OPEN. . .not closed. Is that correct?

-JR

 

[Rex S]

I vote for the fan clutch too. One of the most overlooked items on most cars. The giveaway is cooling above 40 mph OK. Either you have a collection of trash in front or the clutch is going out. Look (or feel at best) on the front of the clutch where the spring is ANY oil and dirt in the spring area is a sign of the clutch going out also ANY play in the clutch its self.

 

[LLC5]

I vote for the fan clutch too. One of the most overlooked items on most cars. The giveaway is cooling above 40 mph OK. Either you have a collection of trash in front or the clutch is going out. Look (or feel at best) on the front of the clutch where the spring is ANY oil and dirt in the spring area is a sign of the clutch going out also ANY play in the clutch its self.

I doubt if it is a debris problem if it cools over 40 mph, but it is definately worth checking. I would start by making sure the fan clutch is in good condition, and that the radiator fan shroud is properly sealed around the radiator, and that the shroud is not cracked or broken. Fan shrouds are as important to evacuating heat at idle as the fan itself is. Be aware that is normal to see higher than normal coolant temps in high ambient and humid conditions.

 

[Bolisk]

I should have been more clear about cooling over 40 mph. When I said that I mean that the temp needle droped out of the red, but was still EXTREAMLY HOT. Fan shrowed is new, and the seals arroud the radiator are also new. I had all of the cooling system replaced when I bought the car. In three years it never over hearded even on the hottest days. Untill this past sunday. . .so I agree it was either the fan, a stuck thermostat, lots of crap in the block. . .or all three.

At any rate, the fan clutch appears to be fine. No play. . .nice drag. . .but I will keep an eye on it.

I stoped by the local vett shop last night. . .and the owner said that there shoun't be a 40+ degree differnce between the thermostat housing and the hose only 4 inches away. Suggested that I replace the thermostat and flush the cooling system, but said that I should drain the block before the radiator, as chances are there is lots of rust and scale that is built up in the block over the last 20 years (since the last rebuild). . .and it's gotten to a point where it clogged or jambed the thermostat. . .and said i didnt' want that to backwash into the radiator.

Since my block had two petcock drains on either side. . .this was easy for me to do.

Sure enough when I drained the fluid. ..it was so fully of crap that it wasn't really green anymore. . .it was a very dark brown with a green undertone. Lots for particles of rust and crap in the anti-freeze. It was so bad that the drain plugs kept clogging. . .I had to pull the petcocks off, and unclog the block with a mini screwdriver.

When I changed out the thermostat. . .sure enough there was a bunch of the came crap wedged in the gaps on either side of the robert shaw thermostat.

I put two bottels of the Flush in the radiator. . .and filled it with hose water. Burped the system. . .then went out and beat on it for a good hour and a half. The car never went over 190 in temp. Granted it wasn't 90+ degrees out last night. . .but it was still in the 80's. Tonight I'll drain the flush. . .then fill it with hose water. . .beat on it. . .then drain it and put in fresh anti-freeze. With any luck this will have solved the problem.

Thanks for everyones help!

 

[74bigblock]

So, in summary you could say... you were full of crap?!



Nice to see another NW Suburban Chicago person on the CAC!

 

[LLC5]

Glad you found the problem. That is a lot of debris in the coolant, I can understand why it wasn't evacuating much heat. Completely flushing the system as you just did at least twice a year until the coolant stays clean consistently would be a good idea.

 

[Bolisk]

otfl Yes. . .completely full of CRAP!!! otfl

 

[Bolisk]

I won't say I found the problem until I'm able to drive the car in an aggressive manner in 90 degree plus days. Once I can do that with the car staying reasonably cool. . .then I will say it's solved.

Speaking of which. When i replaced my lower radiator hose, I noticed that the new one didn't come with the spring thing in it. So I took the old one and put it in the new. The old one. . .wasn't in great shape. . .but I figured it was better than nothing. Not sure I need it.

Good idea on flushing a couple of times a year. I'll see how things go with this. . .and keep and eye one it. At the very least.. .I'll do it once a year.

 

[LLC5]

I won't say I found the problem until I'm able to drive the car in an aggressive manner in 90 degree plus days. Once I can do that with the car staying reasonably cool. . .then I will say it's solved.

Speaking of which. When i replaced my lower radiator hose, I noticed that the new one didn't come with the spring thing in it. So I took the old one and put it in the new. The old one. . .wasn't in great shape. . .but I figured it was better than nothing. Not sure I need it.

Good idea on flushing a couple of times a year. I'll see how things go with this. . .and keep and eye one it. At the very least.. .I'll do it once a year.

That spring is good to have in place, I would want it in. OEM hoses usually do have it to keep the hose from flattening. Good luck with it, hope you are done with overheating.

 

[navy2kcoupe]

That spring is another good reason to keep the antifreeze/coolant up to snuff. The new stuff will have all of the rust inhibitors in it to protect that spring as well as the rest of the cooling system. Old coolant looses it's rust inhibiting ability. The spring prevents the lower hose from flattening out under acceleration (or sustained highway driving) and causing overheating.
Andy

 

[tracksnblades1]

Don't overlook the benefits of using distilled water and antifreeze mixtures of less than 50-50 to cool the hard to cool beasts. Chlorine is not a welcome element in cooling systems or humans especially at 286*. Antifreeze does not have the heat conducting coeffecient of water no matter what the hype on the jug says. Copper has the 4th lowest resistance to heat transfer. Behind Platinum, gold, silver and ahead of aluminum. Distilled water is pure h2o no minerals to foam or to form sludge in your cooling systems. A 286 degree reading on the outside of the thermostat housing, WOW! At 286 degrees on the inside of the housing would require a radiator cap with a rating of above 54# to keep it from boiling over with the system full of pure water. It is amazing it didn't sound like a tee pot in an iron forge. Equally you didn't indicate any engine damage. Diesel engine shops have easy to read test strips to check the condition of your coolant.

 

[Bolisk]

After flushing the radiator completely.. .and putting a new thermostat in it. . .everything appears to be fine. No known engine damage. . .as a matter of fact, the car runs better than ever. . .untill by clutch broke. I'm trying to fix that before bloomington gold next week.