herdez55

Hello,
I'm new to classic Olds and to older cars in general, my father and I recently purchased 73 Omega with a 350. The car is in good shape and drives great, the only problem is that it runs hot usually at highway speeds it starts to overheat. I have replaced the water pump, lower hose and had the radiator flushed, but the problem didn't go away. I noticed that there is some white stuff build up inside the radiator on the end of the fins. so i took the temp readings at the inlet and outlet of the radiator and the difference was less the 5 degrees. I believe the radiator is the culprit but am also considering the fan clutch.

If anyone can give their opinion on the matter I would appreciate it

Nasty455

Overheating usually is from internal engine friction,worn bearings etc.
Check simple things like restrictions in the hose(spring installed?),fan shroud installed correctly,fan blades should meet at the shroud.
I've seen people add a flex fan which protrudes too far into the shroud and leaves little room for airflow.
Flush the radiator with prestone super flush to remove built up scale.

MDchanic

I agree. If it were the fan clutch, it'd be overheating at idle in traffic, not on the highway.

- Eric

bigD

did you check to make sure there is a thermostat installed?

herdez55

Thanks for the replies,

The car currently has no thermostat, but it overheats the same with it installed. The fan shroud is properly installed, the fan blades are not too far into the shroud. If the radiator is partially clogged would the flush not have removed the material that was clogging it up? Note I did have it flushed at a radiator shop.

MDchanic

Nope. Lots of times it doesn't.

You may need another radiator.

- Eric

oldcutlass

If its really clogged you may need to take it a radiator shop. It may need to be cleaned and rodded.

joe_padavano

I had a very similar problem with overheating at highway speeds (but not at idle) with one of my Chevy trucks. Once the engine was at operating temperature, you could touch the radiator with your hand and tell that the bottom half of the radiator wasn't hot at all. Obviously it was plugged. A new radiator fixed the problem.

herdez55

Ok so I finally got around to replacing the radiator, but that didn't solve anything the problem remained the same. So i figured it had to be the fan clutch, so I blindly went ahead and replaced it too but that also didn't solve my problem. Now I am at the end of the road and I still haven't fixed the car,and only managed to throw the wrong parts at it.

So to recap the car will overheat at highway speeds or when revved up for to long, but it can be left at idle for ever and won't over heat. Have replaced now: Radiator, Fan clutch and Lower hose + water pump. There is no thermostat installed and the timing was set to 8 advanced.

Please any help will be appreciated.

380 Racer

Install a thermostat.

Highwayman

With no restriction from a thermostat the water circulates too fast and doesn't stay in the radiator long enough to dissipate the heat.

MDchanic

+1.

Have you taken a look at the water pump?
Like, is the impeller in good condition?

I'd consider a high-performance water pump with a closed impeller at this point. Also, do you have any idea what the water passages look like inside the block and heads?

- Eric

Nasty455

Fan shroud installed?
Fan blades should line up with the shroud opening.
What are you taking temperature readings with?

herdez55

sorry let me clarify I've tried both ways with and without the thermostat and it overheats all the same. The fan blades are pretty much aligned with the shroud maybe about a half inch or less into the shroud. And I have installed a new water pump as well. I have flushed the system with prestone super cleaner and also the old fashion way with a garden hose but nothing unusual comes out. but other than that I have no idea in what condition the water passages look like.

I have been taking my temp readings with an IR temp gun and of the vehicle temp gauge.

Thank you all for the replies

MDchanic

I had one of these too, once.

'68 88 with a 455, about 20 years ago. Engine was completely original and dealer maintained, so no modifications. Ran great, but got hot in the summer, couldn't use the A/C if it was really hot because the light would come on.

I tried everything, just like you have, and nothing helped.

I finally sold it. Never did figure out why it was overheating.

Now that I think of it, I did the same thing with a '68 Galaxie 390 about ten years ago.
New radiator, water pump, thermostat, hoses, belts. The darn gauge would just creep up on a hot day on the highway.

Sold that, too.

Looking back, my suspicion is that the engines were loaded down with scale.
Both had spent years sitting, or with very little use, and I suspect the water passages had just plum rusted up.

Because of this, my suggestion today would be acid, and plenty of it.
Remove the thermostat, block the lower hose (leave the nice new radiator disconnected), fill it with a strong acid, and leave it for a day or two, then flush the hell out of it. Maybe repeat it after you've flushed the heavy stuff out.
The main risk is that you might corrode your head gasket and cause it to blow. The cast iron of the heads and block will be fine.

I've tried this on a block that was disassembled, but have not done it to an engine in the car.
Experiment at your own risk, and use goggles if you do.

- Eric

herdez55

I don't know exactly how long this car was sitting but it was full of leaves when I purchased it and the tires were 12 years old so I am guessing it was sitting for a long time. Blocked passages is a big possibility at this point. Is there any test I can do to see if the passages are clogged or corroded before I hit it with acid? and can I maybe have a shop do this?

This is the first classic in the family and I would hate to ruin the engine or cause any further damage.

MDchanic

I honestly have no idea.

When I tried it out on a block, I used "muriatic acid," which is hydrochloric acid. You can buy it by the gallon at Home Depot, etc. for adjusting swimming pools.
I rotated the engine stand so the engine was at 45° (head surface horizontal and level), put super chemical-resistant tape that's used for silk screening over the water pump hole, filled it up, and left it for a couple of hours.
It fizzed pretty well, then I removed a drain plug and drained it into a bucket (it made a mess), and flushed it with a hose.
It cleared out a lot of the rusty crud, but would need to be done at least once more.
Note that this acid is very caustic NASTY stuff, and will burn you or blind you, and wreck any metal or painted surfaces it touches.

As I said above, I know that it is harmless to the cast iron surfaces of the water passages, but I am not sure how much time it would need to damage the head gaskets. It's also not great for that new water pump (you could bolt on an old one temporarily), and will etch machined surfaces (like cylinders or bearings) if it gets on them for too long.

It was just an idea, and I'm still not sure whether it's a good one or not.

- Eric

oldcutlass

So exactly what is the temperature you are running at idle, and at cruise?

Nasty455

Remember,once you flush the cooling system,there is still a gallon or so of water left in the system.
Add 2 gallons antifreeze,then top off with distilled water.
adding a 50/50 mix with a gallon of present water gives you an incorrect mixture.

herdez55

At idle the temp goes around 205-210 at highway speeds or when I start to rev it the temp goes upwards of 225 but I know it will keep going higher if I keep driving it.

herdez55

I usually just add 50/50 coolant I don't top it off with distilled water. You think that would be enough to cause it to overheat?

I had a chance to talk to one of the senior mechanics at a shop and he suggested to check for a blockage in the exhaust system but I havent had a chance too check. I dont mean to doubt that mechanic but wouldn't a blocked exhaust system cause the engine to run cooler not hotter because it would cause weaker combustion help? kinda like how the EGR systems helps cool the engine aside from also recirculating combustion gasses.

Now that I'm thinking about this Omega is EGR type could a bad EGR valve be causing my overheating problem?