overheating woes

[jamiep]

From September to November, I took my '67 nova on a 10,000 mile roadtrip from Massachusetts to California and back. It had started running a bit hot before I set off. It used to run around 190 degrees, and was now running at about 210 most of the time. This problem got worse as I went along on my trip. I had my radiator recored in chicago, and replaced the water pump and flushed the system with one of those 10 minute flushing solutions at a campground in Iowa. I also replaced the thermostat and radiator cap along the way, but nothing seemed to change things. It was much worse in the deserts of the Southwest, sometimes getting up to 240 degrees on a hot day. When I came back east, the weather was cooler, so the engine temperature stayed in a more reasonable range. Now the car is off the road for the winter.

My assumption is that the coolant is not circulating through the engine as well as it used to, since pretty much every other variable has been replaced. Having already flushed the system, is there anything else I can do to address this before summer comes?

[Terry29-26]

Hi

Have you put a thermomter in the top of the rad. to see if the gage is corect?

[Guest]

when did you re-core the raditor?

I re-core mine, and was over heating again, 12 months later.

I had to get the new raditor flushed out because an old engine will clog new raditors. Spend $100 bucks and get it flushed again, and I bet it will be fine....

[critterpainter]

Leaking head gasket (combustion leak)....tired and collapsing radiator hoses....glazed fan belt....bad advance unit on distributer.????

just a few of the out of the ordinary caues I have come accross to cause overheating

bill

[jamiep]

Thanks for all the ideas. I'm flushed the system about 600 miles after the recored radiator was put in, so I don't think there was enough loose junk in the system to clog the radiator. Also, immediately after replacing the radiator, presumably before the radiator would have a chance to clog, there was no improvement in the problem.

I have not tested the heat gauge (probably should though) but I'm sure it's running too hot, because even with a new cap, I'm loosing coolant through the overflow when it gets too hot, and that's never a good thing.

In terms of other causes, the fan belt is fine, hoses are new and unrestricted. I haven't seen any other evidence of a combustion leak. I tuned the car up before the road trip and distributor advance seemed fine at the time. I'm not sure how that would contribute to overheating, but I'd be curious to hear the explanation.

Any ideas on the best way to backflush the system in the hopes of dislodging any debris that's clogging things up? I was thinking of hooking a garden hose up to the heater hose fitting. Is there a better way?

[Guest]

since the water flows from the engine to the top of the raditior, you can look at the top of the tubles to see of there are any "corn flake" looking rust chips blocking the cooling tubes.

Also, your timming can be to far advance, it gives you more power, but also more heat. Lugg the engine back, and drive it with the timming retarted, and see if you get the same results.

You did not say if you had a standard tranny, or if there is a cooler for it.

[Charles2]

In my experience, timing that is too far advanced does not cause overheating. If timing is too retarded, as in a stuck centrifugal advance, then you will get overheating. This is caused by slower combustion causing more heat transfer to the cylinder wall.

Most of the time, overheating is caused by a radiator problem. Check other obvious problems first: timing, dragging brakes, defective temp sensor, etc. Then, I would suggest you check your radiator for tube blockage. A block flush can knock loose a lot of crud quickly that can block radiator tubes. A lot of the time, a cooling system flush is done by simply dumping a cleaner in the radiator, running the engine for a while and then draining the dirty coolant by way of the radiator drain cock. What this accomplishes is loosening rust and corruption in the block which then circulates to the water pump. From the pump, the crud and coolant goes to the top tank of the radiator. The coolant goes through the tubes the crud accumulates on top of the tubes, blocking them. All of this can happen enough to affect cooling capacity in an hour or less.

To back flush the radiator, unhook the top and bottom radiator hoses. Go to NAPA or some such and get a radiator flush kit. This should have an adaptor that will fit a garden hose to the bottom radiator hose with a watertight seal. Connect the adaptor and turn on the water as hard as possible and you may get most of the crud out. Also, you should remove the thermostat and flush the block both ways; from the thermostat housing end, and from the lower, inlet end. If you can arrange it, there are radiator/block flushing systems that use both a water hose and compressed air for cleaning. These do a better job. In fact, the best radiator flush job is done by removing the radiator and flushing it with the lower tank on top. This way the big chunks have a better chance of getting out. But, if you are taking the radiator out, why not pay a few bucks more and have a radiator shop take off the top tank and rod out the tubes. Before putting the clean radiator back in the car, make sure you have blasted out the block as well as possible. Good luck.

[Ron Green]

Make sure the radiator cap is of the correct pressure rating and in fact holding that pressure thru a tester. If this is not right your engine can run hotter if a lower pressure. I have had new caps that were bad or did not hold the correct pressure. As stated above the timing if not correct can also cause problems.

If the radiator was recored that should not be a problem since everything is new except the tanks. If it was rodded out chances are cooling capacity may have been downsized depending on how many tubes might have been deleted, if any.

Last year I had a similiar problem only to find out that a piece of rag to stop the dripping was left in when the hose was installed of which was my fault for being in a hurry.

[Jay Wolf]

It may not be the case, but a while back on the Classic Bird List; they were talking about a bunch of defective water pumps (to much impeller clearance). I don?t know if there was any similar problem with any Chevy pumps.

Little birds are known for overheating.

The 4 big things that help are

1. New 4 row HE radiator.

2. Underdrive water pump pulley one inch smaller than stock.

This speeds up the pump and the fan.

3. A water pump baffle (stamped steel that tightens up clearances in water pump)

4. Water Wetter or some other coolant additive. (Several people swear by these products)

most say the lower temp 10 deg.

I have 1&2 in my bird and never had any heat problems.

[Guest DeSoto Frank]

Please forgive the question:

Is this Nova a 6cyl or V-8 car?

Was a six -cylinder swapped-out for a V-8 ? If so, a 6 cyl rad may not be sufficient to cool a V-8...

Another thought...I have a '64 Valiant with 6 cyl & chronic overheating problem.

At speeds below 50 mph, it runs "normal"; if I push it over 55 mph or add loads such as lights or heater, the temp shoots right up to the "hot" mark...

Apparently the stock radiator (barely adequate when new) has become choked w/ crud, and water is not circulating as quickly as needed; radiator will be cool at bottom 1/3 while overheated at top...

Am planning a re-core this spring, with an extra row of tubes in the core (heavy duty).

Also, double check you t-stat...try running a 180 deg stat; if you're running hotter than stat temperature, then there's a problem in the system.

Sometimes rust and crud builds-up in a block to the point where the do-it-yourself flush doesn't work; radiator shops used to have flushing guns that used water + air pressure to flush blocks... the alternative is to knock out the freeze plugs fro mthe block, dig around with wire rods to knock the junk loose, then flush thoroughly, and install new freeze plugs.

Also, the 230-250 Chevy straight sixes were known to develop cracks in the cylinder heads around the four corner head bolts...this might result in combustion leakage into the cooling system....

Try this: run the engine with the radiator cap removed until the engine reaches normal operating temperture ( t-stat open, heat from heater). Stop engine, loosen fan belt, and remove it from the crank & fan pulleys (disables the water pump for this test).

Start engine, and watch at the open radiator filler while suddenly opening the throttle a couple of times; if bubbles appear in the coolant, that is a good indication of combustion leakage past the head gasket or through a crack into the cooling system.

Just a few thoughts...

[Guest Curt Fouse]

It sounds like all bases have been covered. well. almost. I hope there is not too much paint on the radiator core, and also did that new lower radiator have a spring or anything inside it to keep it from sucking shut? I never forgot that a 55 Olds that was not very old would heat up on the highway but stay cool in town. I took it to a radiator shop, they started it up, revved up the engine and pointed to the bottom hose. all of a sudden at higher speed that hose would suck closed. The guy said go get a new hose and it will be OK!

Good luck. Curt

[Guest]

In the 60's when I worked in a GM dealeship every car that came in with overheating that didn't have a stuck thermostat had the core plugs knocked out and the block cleaned as well as the rad. A previous poster suggested this and very few people seem to realize that if the inside of the rad (that you can see) is full of crap so will the block. The dealership I worked in did not ever use any chemical flushes. If things had to be flushed every physical part was opened and cleaned reassembled and flushed with copious amounts of water. A fitting was used so that the city water pressure (about 45 pounds) could be directly connected to the cooling system.

[John McFarlane]

Check that the fan is on the correct way. Some have a 'leading edge' which must be the first edge to cut the air. Sort of like an aeroplane wing. This edge is usually the straight edge. If installed incorrectly, air is still drawn through the radiator but at a reduced rate.

[Oldsmoguy]

It may sound silly but I"ve had bad thermostats right out of the box before. On one other auto forum I"m on there has been as many as 3 stats in a row that were bad. I would remove the stat and do the pan test with a thermometer and pay close attention to the opening and closing rates of the stat.

Just a thought.

[jamiep]

Thank you to everyone who is providing so much thoughtful advice. Let me answer some of your questions:

The engine is the original 6cly 250 that was in the car when I got it several years ago. The temperature was fine for a few years, so I?m pretty sure it has nothing to do with an incompatible engine/radiator combination.

The radiator was fully re-cored. The replacement core was (according to the radiator shop guy) identical to the original ? to all appearances, it is the same.

The water pump was not changed until after the problem developed, and didn?t make things better or worse. I?m assuming it?s not a factor.

The fan is on the right way.

I?ve encountered bad new thermostats too. But in this case, I replaced the thermostat with a 195, a 180, and then finally the 160 I have in now. I did a stovetop test of each before installing (past experience taught me to do this) and they all seemed fine.

Finally, it seems to run hottest at idle and at high speeds If I?m stuck in traffic for more than 10 minutes, I?m in trouble. Also, after extended highway travel (over 2 hours) it seems to just gradually run hotter and hotter.

Based on the information you?ve all given me, I think I?ve narrowed it down to a clogged engine, which is what I originally thought. I?m going to try flushing it both ways as best I can using a garden hose. If this doesn?t work, and I need to take more drastic measures, I?m probably more likely to take it somewhere before attempting it myself. Would a radiator shop be the best place for this? When I asked about power flushing or back flushing the engine at a general repair shop in Utah along my roadtrip, the ?mechanic? didn?t seem to know what I was talking about, and basically told me all they would do is use a chemical flushing solution, such as I had already done.

[Guest DeSoto Frank]

Jamie,

Where you are from (or better, where the car is/was from), is the water supply hard or soft ?

Sometimes, areas with soft water have problems with lime deposits in things like boilers, water heaters, auto cooling systems...

Only physical means (scraping) and/or acid baths will remove mineral scale from the engine block....

[Bernd Marscheider]

May the temperature is ok, but the measurement is not. If the cooling would be faulty, there would be a visible different if you drive fast or slow, or even

if is cold or hot outside. Keep Cool and enjoy driving.

Two-Eighty-Your W116 Site

[Guest]

I would reiterate my earlier comment. Knock out all the core plugs and manually clean all the crud out. Flushing only removes the loose bits. You need to scrape and gouge and poke all the built up deposits. I have seen an engine block full half way up the core plugs. So of course it would overheat. Something to try is to find out how much your cooling system is supposed to hold and try to put that much water in it. We have had engines that were so plugged they were short one gallon in capacity. All that space was occupied by crud in the water jackets.

[Jay Wolf]

Almost funny, (funny if we all hadn't have been there) on the classic bird list there was a guy who has work 2 years to cure his bird running hot. Finally last week he found out his temp guage pegged hot at less than 200 deg.

[Oldsmoguy]

I'm told that NAPA has an engine flush system that works with a garden hose, but I think that if you disconnect the heater, upper and lower rad. hoses, and flush each item seperatly it might help.

I would seriously consider the fellows sugestion about removing the freeze plugs and at least see what is going on inside there. Good thing is that it is a 6 cyl and not that tough to get at most of the plugs.

good luck.

[Guest stude8]

I hope my vote will help swing the election here, I had a Studebaker V8 in a pickup that had similar run hot conditions. The treatment that made the problem go away was the job you are trying to avoid, PULL THE WELCH PLUGS in the cylinder block cooling jacket, get some stiff welding rod to bend into shapes that will allow you to scrape around the cavities that I guarantee will have all kinds of congealed mud and crud that chemicals in a can or water hose flushing won't have a prayer of loosening up.

Yes it is a miserable job, wear elbo length rubber gloves and an old rain coat and be prepared to get dirty wet. When it is done right you won't overheat.

Remember only you have the vested interest in doing it right, a hired hand will just go through the motions to get it done as fast as he can and get back in the shade.

Stude8