C2:67 Is it time to R&R the cooling system?

[Gerard F.]

Took a 300 mile round trip yesterday to the Palo AltoVA from Sonora, CA.

The car is a 67 327/300 HP, 63K miles, original radiator, water pump, fan clutch w/ orig fan, 4 speed wide ratio, 3.08 rear, carb and timing adjusted to original spec, everything is standard, never had the engine apart. Normally just cruising along, I don't push beyond the temperature beyond 180-190, first mark to the left of the top center 210 mark. Actually she runs like a champ. I have an add-on vintage air system which I usually turn off if I get near 210.

Yesterday going down the hill in the early morning, things worked perfectly, nothing beyond 190. But coming back in the late afternoon, outside temperature was about 95, and I started having a good temperature rise going up a hill, would go to 220. Then downhill it would go down to 210 but I couldn't get it below 210.

Usually I cruise at 60-65 mph with the tach in the range of 2000-2500 rpm. Tried cruising in third at 3500 rpm, seemed to help a little but not much, could not get it below 210.

When I got home, I checked the engine at 210 to 220. Upper radiator hose has fat with pressure, some moisture at the end of the expansion hose but no puking of fluid, or leaks anyplace. Let it cool down to ambient and the coolant level was normal.

Am I over-reacting to this, or is it time to R&R the cooling system? What is the first thing to check or replace?

Jerry Fuccillo
#42179

[Duke W.]

Re: C2:67 Is it time to R&R the cooling system?

Is is a 49 state engine or a CA configuration with K-19?

Duke

[Joe C.]

Re: C2:67 Is it time to R&R the cooling system?

Gerry,

Have you had ambient conditions like that before, and coolant temp stayed below 200? I assume that the A/C was off, at least after the temp rose beyond your "comfort zone".

You know that these old cooling systems have very little overdesign for heat rejection. It doesn't take much to overtax them. With that in mind, and the fact that you're dealing with a 40 year old radiator, then I would use a very gentle approach.

First, DO NOT CLEAN/FLUSH the cooling system with commercial cleaners. I would drain it, and remove both water jacket drain plugs. Try to remove whatever sediment that you can with wire. Replace plugs, fill with water, run, and drain, fully. Recheck vicinity of plugs for debris.

Next, remove thermostat and check its operation to be sure that it's opening fully. If the stat is old, I would suggest replacing with a new 180* unit. Inexpensive.......and eliminates one possible problem. DO NOT replace with anything other than 180* stat.

Fill with 50/50 (optimal concentration for best compromise between specific heat, and boilover protection) coolant mix.

Since you have a condenser mounted, you cannot feel for hot spots in the rad. I wouldn't be too surprised if you had some restriction, with a 40 year old rad. An IR sensor will give you a false reading because of the condenser, and is not viable unless you can somehow measure from the engine side.

Good luck, and keep us posted.

Joe

[Kirk McHugh]

Re: C2:67 Is it time to R&R the cooling system?

Jerry,

I don't know anything except my practical knowledge of driving my 67 327/300 with original A/C (so similar configuration), but even your high number does not seem to far out of the "normal" range for running on a hot day and pulling a hill. I drove mine through the mountains of West Virginia last summer and definitely saw almost an identical pattern. When I pulled the big mountains she creapt up to about 220 or a little higher only to fall back down as I cruised down the other side. My car will also run about 220ish if I drive at 70-75 on the interstate for an extended period of time. Now, if I back off to 60-65, she will drop back down after 5-10 minutes at that speed. Heck, seems like no problem to me, unless my car has been running "hot" ever since I got it. My vote, over-reaction, just keep your eye on the needle when driving.

Kirk McHugh

[Gerard F.]

Re: C2:67 Is it time to R&R the cooling system?

Duke,

No AIR, PA car, original distributor and vacuum can restored, initial timing 8 degree BTDC, 91 CA gas.

Jerry

[Phil P.]

Re: C2:67 Is it time to R&R the cooling system?

jerry,try a high pressure garden hose flush from the fan side of the radiator---best if you remove the rad.---i have a 71 350 auto a/c that was acting up temp wise and since i'm not keeping the car i remove the rad. and blew out lots of dirt and bugs from the fan side,it made about a 10 degree difference on running temp---good luck,phil

[Duke W.]

Re: C2:67 Is it time to R&R the cooling system?

K-19 can cause higher temps, especially at low speed, but that's not an issue in this case.

It's amazing how long those OE Harrison radiators can last. Over the years deposits will build up and reduce heat transfer and there's really nothing you can do.

Most modern cars still have 15 psi caps, so the boiling point of a 50/50 glycol/water blend is at about 265F, and they may go up to about 230 before the electric fans engage at full speed, so they can operate at the same temps in similar conditions, especially in low speed driving.

You still have considerable margin to boiling, but some of your cooling system design margin has been eaten up by deposits so to speak.

If you look in your owners manual, I think you will find that it says the temperature range you report is "normal" and if these are the worst conditions you anticipate, then you can probably go a few more years, but you might consider taking advantage on one of Tom DeWitt's occasional specials to order a date coded 316 replacement and keep it around for the day that you finally really need it.

Use Zerex G-05 antifreeze (which will precipitate out deposits slower than "green") and it will likely last longer than many of us!

Duke

[Joe R.]

Re: C2:67 Is it time to R&R the cooling system?

Hi Jerry:

Before you do any major work, check to see whether your temp gauge is accurate. Corvette temp gauges are well known for being inaccurate.

An inexpensive test would be a thermometer in the expansion tank with the RPM cranked up to 2000 or so using the idle screw. I think that gets a pretty good flow through the tank, so that the temp of the coolant in the tank will match the temp in the engine. Of course, to do this test you must remove the cap when the engine is cold and then warm it up with the cap off.

Maybe you can borrow an IR gun that measures temperature. I can loan you mine if you want. The temperature of the thermostat housing and upper radiator hose should closely match the reading on your gauge.

[Gerard F.]

Re: C2:67 Is it time to R&R the cooling system?

Joe,

I taped the wife's meat thermometer to upper radiator hose. The gage works good, but unfortunately I had to buy the wife a new thermometer.

Getting ready to do a flush of the system. I scored a rebuilt 608 water pump, within about two months of my engine, on ebay from a famous denison here. Also have a repro lower hose with new dated clamps, 160 thermo, and two gallons of Xerex G-05. Figured I'd do a minor R&R with the flush. Got some good advice here, and one of these days I'll order a replacement radiator to put on the shelf for that inevitable day when the original springs a leak.

Would you believe I have my 40 year old water pump and lower hose still on the car. The markings of the lower hose look quite different than the repro. I can make out GM in larger letters than the repro, and it seems to have a stripe. The repro has a part number and no stripe, and I don't see any part number on the original as yet. I'll have to do a closer comparison once I get it off. It will be interesting to see what the inside of that water pump looks like.

Saw you in the pictures posted from Carlisle, did you find the correct kick panel screws?

Jerry Fuccillo
#42179