Runs hot with new radiator

[Brian K.]

66 327/300 no air. I put in a new Dewitts correct radiator because the original was weeping & running a bit hot in traffic. All new hoses, 180 thermostat, flushed super clean.

Now it seems to run close to the 210 mark (around 200) at cruising but cools down when idling. I don't get it. It ran cooler in general with the old one just not good in traffic on hot days. Now it's hot at cruise speeds & cools when idling.

Can timing affect temp that much? It was pinging more than it ever had but I attributed that to the high running temp.

Thanks for any help!

[Jean C.]

Re: Runs hot with new radiator

Brian,
Timing can certainly be the culprit when an engine runs hot. I have no explanation of why hotter at speed than at idle but possibly related to a timing issue. Duke will explain it.

Why a 327/300 is "pinging" in the first instance would be a good indicator to me that something is haywire. I run 91 / 93 octane in my '64 with a 327/300 but never have pre-ignition problems. Have also run mid-grade fuel with no problem.

Best regards,

[Bill C.]

Re: Runs hot with new radiator

Did you check the thermostat operation before installing it?
I have had them not fully deploy open or act funny while going through the heating process. Just because they are new, no guarantee they work okay.

Is there any chance the fan clutch is not working correctly?

Just some ideas....

[Tom M.]

Re: Runs hot with new radiator

Does your radiator cap work?

[John H.]

Re: Runs hot with new radiator

Now it seems to run close to the 210 mark (around 200) at cruising but cools down when idling. I don't get it. It ran cooler in general with the old one just not good in traffic on hot days. Now it's hot at cruise speeds & cools when idling.

Brian -

Have you verified the temp gauge reading vs. an I.R. gun shot of the upper radiator hose just above the thermostat housing so you know what the gauge is really telling you? You may not have a problem at all. Corvette temp gauges are notoriously inaccurate (read hot), especially if the original sending unit has been replaced.

[Tom L.]

Re: Runs hot with new radiator

As I was taught, did you run the engine after filling the system with coolant until it got to temp withpout the radiator cap on until coolant is flowing throught the entire system so that all air is "burped" out ?

Hope this helps. Have fun!!

[Duke W.]

Re: Runs hot with new radiator

Brian,
Duke will explain it.

I've explained it a zillion times. It's someone else's turn. How about you?

Duke

[Timothy B.]

Re: Runs hot with new radiator

Brian,

Make sure that system is full of fluid, you may have air somewhere. Double check your inital timing so it's about 8-10* BTDC and verify the vacuum advance control is correct for the distributor and is working..

Total idle timing (inital + vacuum advance) should be approx 25*

All the suggestions above are good, did you change out any other parts? Does the radiator cap hold pressure OK?

[Stephen L.]

Re: Runs hot with new radiator

Did you flush the block? I found a LOT of rusty scale in my block, especially near the "frost plugs". It took a lot of flushing probing etc to get the trash out.

[Donald L.]

Re: Runs hot with new radiator

As far as your detonation perhaps your ignition map is too aggressive. Duke mentions that you should bring the total timing in as soon as possible for best low end torque with detonation being the limiting factor. Check to see at what RPM the total timing maxs out. For base engine something over 3000 RPM is about right.

[Brian K.]

Re: Runs hot with new radiator

Thank you all for the help. I haven't checked in here for a few days. Cap is good, clutch should be good as it was before the new parts (remember, this is a change in operating temp since the new parts), system is burped, flushed to death, I do have an old style thermometer that I can stick in the tank. Have to check that. Did not test the new thermostat.

Will check the timing over the weekend & post back.

Thanks again

[Jack H.]

Re: Runs hot with new radiator

Caution! You can't realistically stick a thermometer in the tank... Why?

You have to remove the rad cap to do that. Once the cap is removed, the cooling system is open to the atmosphere and no longer under pressure. You're working with apples and oranges, then...

[Timothy B.]

Re: Runs hot with new radiator

Brian,

If the radiator has been replaced with a DeWitts aluminum radiator it is cooling better than before... If the system goes under pressure when hot I would verify temperature with a IR gun first before assuming anything is even wrong with the car..

[Duke W.]

Re: Runs hot with new radiator

[quote=Brian Kane (47891);
Now it seems to run close to the 210 mark (around 200) at cruising but cools down when idling. I don't get it.
Can timing affect temp that much? It was pinging more than it ever had but I attributed that to the high running temp.

[/quote]

That's opposite of typical. As with virtually any overheating problem, one of the first things to check is the spark advance map. The above symptoms could by caused by a stuck/sticky centrifugal advance.

The specs which make up the spark advance map are in your '66 CSM and '66 AMA specs. It's not just "initial timing".

You'd be amazed how many of these 45 year old cars have had no distributor inspections/maintenance other than new points, cap, and rotor since new. It's a simple component and easy to do basic checks even without tools or test equipement.

Duke

[Chuck R.]

Re: Runs hot with new radiator

Hi Brian,

IPull the thermostat and take it for a drive and see if it runs cold.

If it still over heats, then consider colapsed or pinched hoses keeping in mind that a hose can look fine idling but under high rpm conditions, they can squeeze down restricting flow.

Was the coolant replaced and if it was, was it a 50/50 mix?

I'll go out on a limb here. If the fan was removed, could it have been re-installed backwards? I had to ask

Chuck