Hello All,

I have a 1971 coupe with a GM Goodwrench 350. 8.5:1 Compression, Edelbrock Alum heads, valve covers, intake, 650 carb. P/S, P/B, A/C. There is a new aluminum radiator, fan, and shroud. The engine has around 30K miles on it. The issue is the temp flux. The temp rises after starting and overshoots 220 degrees. Sometimes going almost to 250. After a moment or 2 it will fall back down to 200. When driving it will climb back to 220 at times, then fall back to 200. Runs at 220 with A/C on. Will climb higher if I run the car hard. Over the last 2000 miles the water pump gasket sprung a leak and there is now coolant leaking from what apears to be under the passenger side valve cover. Otherwise the engine runs great with plenty of power and no smoke in the exhaust. Does not seem to be coolant in the oil or vice versa. I assume the coolant leak issues are related to the high temps. And I hope that they are gaskets related and not cracked block related. Could this just be a Bad Thermostate or something more problematic?

Thanks, Scott.

 

My guess is a sticking t-stat is it's spiking quickly and falling quickly.... the leak sounds like head gasket if not from the temp sensor threaded in the head....when you say below the valve cover (side or front), head gasket would be about 4-5 inches below valve cover. Other possibility is the water pump leak is flowing/blowing around to the side and looking like additional leak.

 

Change the stat to a Robert Shaw unit.
Just rent a pressure tester, place it on the radiator, pump it up to 20lbs, and look for the leak.

 

also, just remove the thermostat and see how it does without a thermostat. let us know.
yes, rent a pressure tester and find your leak.

if your coolant level is low, your water pump will be sucking air and you will get spikes in your temperature. plus your thermostat will not be able to accurately sense the coolant temp.
another solution would be to drop your thermostat temp a notch or 2.. if you have a 195 in there now, install a 180 or a 160

 

Does your lower radiator hose have the spring inside?

 

good points

 

All of the above are valid suggestions, and I add to drill holes or trim the skirt of the stat, allowing superior flow, but slower warm up.....this due to the silly .gov regs all the stats have smaller flow ports, regardless of when the stat opens......I noticed this many years ago, the old 160-180 stats had much larger flow ports.....

and I went though this over the last 8 months or so, and found MY final solution was change the water pump.....

 

Gene,
I just installed a Stewart. Had to modify the smog pump bracket, but I still love the pump. Flows like a banshee, and draws only 2hp. Weighs like 2 lbs.

 

dont have to see smoke to have a blown HG
if its coming out of the valve covers time to tear things down
drive it long enough with coolant in the oil your bearings will eat themselves

 

No Idea. What is this for?

Scott

 

Water Pump gasket was replaced just a few weeks ago. The coolant is pooling on the back inside corner of the intake manifold.

 

Under high RPM, the water pump can actually suck the hose flat, restricting flow and overheating at speed. When you slow down, the hose expands, and the motor cools off.
I have seen Delco hoses with the spring, and supposedly replacement hoses without. Gates says their hoses have stiffer rubber, and do not need the spring. But oil softens all hoses, and the collapse can occur.

 

Makes sense. Thanks for the explanation. Would I be able to feel/see the spring through the hose, or do I have to disconnect to inspect?

 

You can feel it. And you cannot squeeze it closed, like you can the top when there is no pressure.

 

Thanks,

I saw this in a youtube video, but it seemed a little ghetto. I don't mind longer warm up, but want better cooling. I got the car in the fall. It ran fine when it was cold out, now I am having issues. Went for a drive today and the goopy foam insulation on the A/C line melted off.

Scott

 

Hello All,

So I should have replaced the thermostat.... First the the water pump gasket blew. Then there was another leak somewhere on the passenger side. At first there was a small amount of coolant at the rear of the valve cover on the intake manifold. Then after a short drive there was coolant spewing all over from that general direction. Enough to make a large puddle on the ground. I hope/assume from the head gasket. There does not appear to be coolant in the oil, but may be oil in the coolant. I have not driven it since then. See, I'm learning.

Current configuration.

Replacement Engine has Mexico made GM Goodwrench 350. PO installed Hooker Headers/Sidepipes, Edelbrock Dual plane intake, Alloy Heads, Carb, MSD ignition. Aftermarket Cam - although not very aggressive. 8.5:1 compression. Current Muncie M-21 and poweer steering both need an overhaul.

So I am all over the map, but here are my options.

1 - Replace the head gasket myself to save $$$. I have read a bunch of how to articles/posts on replacing the head gaskets. From what I can tell the only real challenging part is dealing with re-installing/adjusting the valves. Any feedback on this would be great. My skills are good but my work space is limited. I have a small reserve of cash, but I would rather spend it on Engine upgrades and trans/steering repairs.

2 - Find a good engine repair place. I am not happy with my regular guys. I had them replace the water pump gasket and they left the car outside in the pouring rain after we discussed how the t-tops leak. Water all over the inside. So I am looking for a good performance engine place near Bala Cynwyd PA - western suburb of Philadelphia - that can replace head gasket.

3 - Complete engine overhaul / crate engine. Considering a 383 complete crate engine. Could do something more custom and use the top end from my current engine on a stroker block and pistons. Still need to find a good mechanic.

Thanks for advice in advance.

 

If you cant find someone closer

 

if you don't do it yourself, then paying someone will cost you over a grand after they upsell you on hoses, other gaskets, flushes, clamps, new bolts, antifreeze, filters, other "while it is all apart". may as well spend 3k on a 383 short block

but how do you know it is a head gasket?

 

So I jury rigged a pressure test. Purchased cheap radiator cap. Cut out inner spring/seal. Inserted cut off valve from bicycle tube into end of overflow tube and inflated with bike pump to 15psi. Sure enough, coolant started leaking from intake gasket passenger side rear. Pulled bolt and applied sealant but leak continued. Purchased new intake gasket and thermostat, and replaced both. Checked new and old thermostat in boiling water. Both are 180 degree and seemed to work fine, but I re-stalled the new one. Found no oil in coolant or vice versa so I put it all back tofether. No leaks now, but TEMPERATURE IS STILL FLUCTUATING! What is up? Temp guage seems to stick and jump. Will run at 200, then creep up to 220, then jump back to 200. Runs hotter with A/C on - closer to 220. What should I check next?

 

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​verify the sender is working right, use a infrared thermometer and compare temps. Where is the sender, in the left head?