70 350 Cutlass S

So I am brand new to the Olds Cutlass world...
I just picked up a 1970 Cutlass S. Problem is it keeps overheating. I changed out the t-stat twice, first with a 195, now a 180. Changed the water pump and the fan clutch. I drive it 3 -4 miles and the overflow jug is just boiling mad!
Today I decided to drive it to work (2.5 miles) and a couple of errands throughout the day (maybe 10 - 15 miles). All day I ran the heater (even though its 107 outside today!). No problems all day. This evening I was cruising around and when I was 1.2 miles from the house I switched over to A/C and within 30 seconds, it was getting hot. Pulled in the drive and the overflow was filled and boiling again...
It's driving me mad trying to figure this out... any pointers are welcome!

PLEASE HELP!!!

PS The car has been sitting in a garage for 3 years undriven or started. Since Friday it has also got a new battery, radiator flushed, oil changed...
My thought is it could be the heater core, but I'm really unsure of where to go next... HELP!

CQR

Not likely a heater core causing an overheat. Have you checked the fins of the radiator for debris? The A/C condenser can look clear but the rad fins can get a lot of fuzz/ hair/leaves/etc and cause an air flow problem. Also, Does your radiator cap hold pressure?

MDchanic

Is it overheating or is the overflow bottle filling up?

You said nothing about the engine temperature - only the overflow bottle.

Is it filled with 50:50 water:antifreeze?

- Eric

70 350 Cutlass S

I have fully washed out the fins... as I use the hose when it is overheating...

Not sure about the actual temp (no gauge).
It is filled with 50:50 water/freeze

70 350 Cutlass S

And yes it is the overflow bottle only... Cap seems fine, but maybe I should replace as I have not done so yet....

Also, I didn't mention it is a 350 2bl, pretty stock Cutlass S

70 350 Cutlass S

Yes, the cap is holding pressure. Its filling the overflow so much, it blows the small tube off and the fluids are TRULY BOILING.

W70442

See if you can borrow an infrared thermometer from a friend or go to a garage and see if they'll let you use theres to check the actual temp at the goose neck/thermostat housing. Then at the radiator itself on the input side and also the output side. There should be at least a 20 degree drop from input to output.

The fan clutch may be bad keeping the clutch from ever engaging. Haven't checked the Olds manual but my 78 Pontiac manual has a procedure to check the fan clutch. Basically, from a cold engine, start the car and idle it at about 2000 listening to the engine for fan noise. Within about 9 minutes, when the engine reaches a certain temp (190?), you should hear a noticable "roar" when the fan clutch engages. If you never hear a change in the fan noise, the clutch is probably not engaging.

Some other things to check are that the lower radiator hose HAS the spring inside of it. If you squeeze the hose a few inches away from the water pump, you can feel it inside the hose. If it's not there, that hose can collapse seriously restricting flow. Maybe completely.

The carb running too lean can cause the engine to run hot. I think too much timing advance can also cause it to run hot.

If you or anyone recently changed the coolant, ther may be air pockets in the engine. The engine may need to be "burped". Basically park the car at a severe angle with the front end high with the engine running. This will help move the air pockets out of the engine and into the radiator.

Since the car is new to you, there is the possibility that someone installed the wrong size water pump pulley under driving the pump.

The fact that it doesn't over heat with the heater on means that water is flowing to some degree through the core support and therefore the cooling system in general.

There's a zillion possibilities but these are some possibilities.

70 350 Cutlass S

The guy I bought it from ran this as his daily driver up until 4 yrs ago. I replaced the water pump and reused the pulley that was on it. I'm open to size suggestions on this one!
Last night when it overheated while driving 5 miles, I did notice that when I was cooling the rad with a water hose, the upper compressed severely until almost flat, then after 2 or three minutes, relaxed...
Any chance it is the radiator itself?

BTW- thanks in advance to any/all with their suggestions... like the post title- I'm desperate for a solution...

70 350 Cutlass S

Another note/detail. When this all starts, the oil indicator light comes on, not the temp light on the dash...

W70442

Makes me wonder if the wires to the sending units are switched. The temp wire is green and the oil pressure wire is blue.

And, yes, the radiator could absolutely be the problem. Checking the temp drop from input to output would be a good to check. If there is NO drop in temp from the input side to the output side, it could be that the fan is not pulling the air through(fan clutch) or the radiator is clogged inside. The fact that it sat for several years could have caused some build up.

MDchanic

The first place I'd look is the cap.

Easy boiling (low cap holding pressure).

Easy coolant blow off (low cap release pressure).

Vacuum valve sluggish (won't allow air in as engine cools, causing hose to collapse).

- Eric

70 350 Cutlass S

Thanks for the post! I will pick one up tomorrow...
About the Vacuum Valve.... Does it require more use when you kick on the A/C?

defiant1

Out of curiosity, did you open the plugs on the block when you flushed/cleaned out the old coolant? After I bought my car, I flushed the system and I had some pretty awful junk come out of the block. Also did you double check to make sure no air in the system?

d1

70 350 Cutlass S

No, I didn't... Can you expand on that? Specify location & quantity of plugs?

BTW- Beautiful pic of your Cutlass S...I see mine very similar in the future (after paint!)

Lady72nRob71

Do get an infrared thermometer to check the temperature.
Most tool stores sell them now. VERY handy for home and automotive use!

Block drain plugs are the 2 funky looking hex bolts on both sides of the engine, right above the oil pan towards the front. You might have to scrape your way to them.........

sicky olds

did you get the radiator pressure tested? had the same problem in the H/O when i got it and replaced it all and then found out the radiator was 50% clogged with build up and such.

MDchanic

The radiator cap has essentially three components:
A pressure relief valve that allows excess pressure to blow off when the set pressure (15psi) is reached, and so keeps the coolant at the set pressure,
A blow-off mode, where it will blow off excess coolant if the pressure is really high (kind of the same thing as pressure relief, but on a completely different scale, and with the valve open further), and
A vacuum relief valve that allows air back into the system as the engine cools, so that you don't collapse hoses, etc. If you have an overflow bottle, then this valve lets the system suck water back in as it cools.

- Eric

My442

You need to check for exhaust gas in the coolant. You can get a cheap kit at any parts store.

A cracked head or blown head gasket will pressurize the cooling system.

rustyroger

I'd have a bet the radiator core is clogged, corrosion builds up over time and flushing won't shift it.
I have come across this lots of times with cars that have sat idle for a long period, especially if the cooling system has been dry. Your hoses pressurising and collapsing is another symptom.
The fact that it gets worse when you use the A/C also points to the radiator.
Could be the hoses are part of the problem as well, if the car hasn't been used for 4 years I suggest you replace them anyway.

Roger.

Rickman48

Replace those hoses with some 'spring loaded' ones - no flow when collapsed, and the springs hold them open!
If the oil light is coming on, you're boiling the oil!
Get some good quality 40 - 50w oil until this is solved!!!

Since it's been around 100 degrees down there, top-notch systems almost gotta be perfect, and I wouldn't drive it until solved!!

70 350 Cutlass S

Thank you, thank you, thank you!

Everyone has had some great input on this issue! I really appreciate everyone's efforts!
I'm going to take it to a Rad shop today, get it checked out. Gonna replace the cap & the hoses... I will update to see what is found!

hookem horns

"I did notice that when I was cooling the rad with a water hose, the upper compressed severely until almost flat, then after 2 or three minutes, relaxed..."

I would replace this hose before going to the shop, especially since you already did water pump, t-stat, fan clutch, etc. Restricted flow through that hose may be it.

455man

How many miles on the motor? Could be just low oil pressure when it gets hot. Try thicker oil. Does it get hot on the highway in red light traffic, or both? Without a set of gauges, it's tough to tell what's going on. I'd put a new cap on it. They are cheap.

Bayou Olds

X2
This was my first guess. Having sat up you could have some pretty serious blockage that a simple flush will not unclog. I have seen friends chase this same issue in the same manner and say "But I flushed the radiator". Pressure test it!

joe_padavano

For future reference, unless you snap the shaft there's no way a water pump can cause overheating. The normal failure mode of a pump is that the bearings go bad, the seals immediately follow, and coolant runs out onto the ground. If that isn't happening, the pump isn't bad.

The most likely causes are an internally blocked radiator or a bad t-stat. I've had a radiator that looked fine but the bottom third was plugged, causing an overheating problem.

midrange

I have to respectfully disagree with this. I had temp/overheating/flow problems with my 71 Cutlass 455.
I changed the t-stat, flushed and pressured tested the radiator, replaced both hoses, and still had temp swings from 200 to 250 at speeds under 35mph. Over 35, the temps stayed steady at 210 even with a 180 t-stat.

When I pulled the waterpump (I now regret not taking any pictures...) but the impeller and vanes looked like this, no 'scoop' to them, they were more like tabs:

Waterpump.jpg

After installing the new pump (with a stamped impellar), the temps now stay at 190 no matter the engine speed or outside temp.

But, as they say, YMMV.

CQR

Agree^^^ I have also seen the pressed on impeller loosen/crack and fall off the shaft. the shaft spins, but the impeller doesn't. It rare, but does happen. I'm fighting a neon over heat right now that is not apparent either.

rustyroger

Worn impellers were a problem with some UK market Nissans as well.
2.5 liter BMW diesels notoriously are known to shear the water pump impeller as well.

Roger.

CutlassLegend

Cheap old timer trick. Full antifreeze with with coolant additive such as Royal Purple, Purple Ice additive and run with no thermostat. May be a pain to warm up in winter but then again who drives these babies in the ice cold winter. This is just a cheap fix and I can almost assure you that it will work. If there is no oil in your coolant or coolant in your oil system then this may be a great fix for you with no long term negative side effects. Dont forget Oldsmobiles tend to run hot.

70 350 Cutlass S

The radiator cap seems to the the correct answer for right now!

Again, I'd like to thank all of you for your suggestions!

MDchanic

Just to clarify (for future readers): Are you saying that you replaced the cap and your symptoms improved?

- Eric

BlackGold

Running without a thermstat does not just affect winter driving. It will take f o r e v e r to warm up in the summer, too. Might never reach proper operating temperature.

If you can run without a thermstat and still achieve proper operating termperature (let's say 180 - 195), that means your cooling system has serious deficiencies -- which means that removing the thermostat is not a fix, it's just a bandaid.

rustyroger

X2 on keeping a thermostat in the system, running overcooled is a good way to rapidly wear cylinder bores.
The engine is designed to run at around 180 degrees, if it is run significantly cooler the carburettor will never be tuned correctly.
Identify what is causing your overheating (my money is on a clogged radiator) and fix it, spending a bit of money now to do it right will save $$$ in the long run.
Roger.

4rims

Not sure how much this helps....I have been told to drill a small hole in the thermostat (weep hole) to remove any air in the block before the thermostat opens. This assures contact of the coolant at the the thermostat instead of trapped air.

Dave

dingusboy

You could try the aspirin trick.
https://classicoldsmobile.com/forums...uestion-s.html

firefrost gold

check timing if it is re-tared to far from a ailing chain set it can over heat from that too. are you sure no leaks a small leak will over heat too

rustyroger

Did you fix it?.
Roger.

oldsguybry

is the radiator plugged up ?

brown7373

I'd bet the radiator is partially plugged. Years ago, radiator shops advertised "We Rod 'em", and I thought it was some kind of high performance upgrade. But they removed the side tanks and pushed rods just slightly smaller than the radiator passages, removing all the hardened sludge and corrosion. You only have to have a radiator 10-15% plugged to start having over heating issues. I'll bet yours is more plugged than that.

Most shops don't rod them anymore, because so many new cars use plastic tanks. I think you may need a new radiator. I bought one that looks identical to the oem for less than $200.00 delivered in a couple days.

revon

After reading through the thread, I believe he said he was going to replace the cap and see if it resolves it. However, I don't think it will. I also read that the water pump will only be determined bad if the seals and bearings blow out, just shy of the shaft breaking, I also, along with a few others, disagree since the impeller can and has been known to deteriorate, thus no coolant flow or movement. A few people have mentioned this, and as a tech that has been around for 42 years, if the car sat for 3 or 4 years, then a few things would have happened. Whatever was floating around in the coolant would have settled...... in whatever part of the cooling system they were floating in at the time circulation stopped. The jackets in the block could have an inch of sediment behind the "freeze plugs". When an engine gets rebuilt and it gets hot tanked, the hot tanking action not only degreases the engine, but the caustic will boil and in some cases, desolve the finer metal sediment. Regardless, it, for all intensive purposes, "washes" all the sediment out of the block. Now, a few of the guys mentioned it, that the radiator core could also be clogged. It maybe clogged by sediment, but also by corrosion. The corrosion comes from the use of dis-similar metals, meaning the block is cast iron, and the radiator, at least back then, was copper, the coolant would be the catalyst to cause the electrolysis to occur. This happens a lot with boats in the salt water, brass prop, steel prop shaft, alum housing. The copper would basically clog by something similar to calcification or when the radiator is drained, you can look down in there and see white crusty crap on the ends of the tubes. Now someone else mentioned getting the kit to test the coolant for exhaust gases (in the coolant). Good idea! IF the coolant was expired, and was below being weak, it might not have protected the cooling system when it got too cold out, and yes it could have cracked a head. Also, again the head gasket could have rotted from the dis-simailar metals situation. These cars usually didn't have an issue with head and intake gaskets like the fwd 3.1 motors.