The Stovebolt Site Forums The Shop Area Engine Shop 235 overheated

Hello I need suggestions
I have a 52 Chevy truck with a 235 last summer my water pump started leaking as well as the lower radiator hose.
So installed a new water pump,pulley,fan blade,upper,lower hoses,belt,thermostat and housing,overflow tank. haven’t ran the truck much since last summer
I had only water in the radiator the plan was flush and add coolant if no leaks in the system so today it was around 90 degrees
Was running the truck in my driveway for about 20-30 minutes than it boiled over I pulled the thermostat tested it and it’s working just fine .I haven’t checked the timing because truck seems to be running pretty good.
I did put plugs where the water would go to a heater do I need to put a short hose so the water would run trough it?
Thanks

What was the indicated temperature on the dash gauge when the cooling system "boiled over"? Chances are there was an air bubble trapped in the cylinder head when you filled the cooling system, unless you drilled a small vent hole in the new thermostat, or "burped" the system by loosening the upper hose as you filled the radiator. Unless you could confirm a coolant temp of 200+ degrees in some way, it probably wasn't actually boiling. Expanding air can push coolant out of the overflow, especially if you have a "zero-pressure" system, or maybe a 4 pound radiator cap.
Jerry

No hose is needed. Some trucks didn't have heaters and the engine doesn't know the difference.

What do you mean by "boiling over"?

Is your overflow tank a reservoir? By that I mean does water flow back and forth from the coolant reservoir to the radiator when the engine heats up and cools down?

No drilled hole in the thermostat didn’t think to look at the temp gauge will be looking at the radiator cap to see if it has lbs numbers when I drained the radiator very little rusty water came out.is a small hole drilled into the thermostat since I have it out?

Drill a 1/8" diameter hole near the edge of the stat, away from the part that moves and allows the coolant to flow at the correct temperature. The hole prevents an air bubble from getting trapped in the cylinder head as the radiator is filled. Another sneaky trick is to leave the upper thermostat housing off as you fill the radiator slowly, and let the radiator, block, and cylinder head get full before installing the thermostat and upper hose, then topping the coolant off. That absolutely prevents air from getting trapped under the thermostat.
Jerry

I’ve never devoted much thought to trapped air in my cooling system. I assumed drilling the t stat took care of any concerns there.

My 235 likes to puke until it’s slightly below the top row of radiator tubes. And I do have a recovery tank with an outlet.

Is that a sign of trapped air in my system?

Hello, I have the same problem since I changed the water pump and the thermostat on my 235. I am still below the top row of radiator tubes after a few kilometers and I consume 1 liter of coolant?

@+ pascal

It is more of a sign that the recovery system isn't working right. Is the radiator cap designed to recover coolant? The way to tell is that it will have a spring loaded "plunger" with a rubber gasket AND another rubber gasket on the underside of the top of the cap. If that gasket isn't there the radiator won't pull liquid back in from the recovery tank as the radiator cools off. Leaks in the recovery system can also cause air to be pulled back into the system.

A good system will purge the air in the engine after a few cycles of running and cooling off. It will leave the top tank of the radiator full of coolant after the engine cools off.

You might try parking the truck on a steep uphill grade and running the engine thru a few heat up/cool down cycles. That should get any air trapped in the engine into the radiator upper tank where the coolant recovery system can eliminate it.

My truck is a GMC. It has a pipe plug in the head above #6 cylinder that are used in some models to mount the temp sensor. I don't know if the Chevy 6 cylinder engines have a similar plug. When refilling the cooling system, I park the truck on a steep incline with the back end high (make the rear of the engine the highest point in the engine) and loosen the plug above #6. When it quits bubbling (all air out of the block) I tighten the plug.

Thanks, Bill. Do I need something different than this?

That's the right kind but it looks pretty grungy. It looks like the rubber gasket is missing from the top. Buy a new one.

Was there ever a top rubber gasket on those types?
Looks like the ones I have
Ain’t nothing wrong with old
Don’t tell the women that anyway
I love the old parts more than new ones
Clean em up good and check function and they are good for another 70 years
-s

Gasket is still there. But it’s probably decades old.

Get a zero pressure one?

My truck has a 4 lb cap and a recovery reservoir. It works great.

I also have a “recovery reservoir”. It’s an antique freezer jar that is hooked to the radiator overflow and also has an overflow of its own. It does take on coolant and the coolant siphons back in as the system cools.

However, this thread makes me wonder if the excessive puking/low coolant level is a function of the system sucking air somewhere.

In my simple brain, you would need something more than a zero pressure cap for the system to recover coolant from the reservoir. But I also know that the early heater cores do not respond well to pressure. Need some guidance on the right way to approach this problem.

The "zero pressure" radiators with a canister on the top tank that resembles a tuna fish can have a "one way" relief valve- - - -I don't believe they will siphon coolant back into the radiator from a catch can. The fill cap on that type of radiator seals tight- - - -it has no springs, siphon valves, or pressure relief valves. If you install a pressure type radiator where a zero pressure system once was, don't forget to also upgrade the heater core.
Jerry

My radiator is an OE copper/brass reproduction of the original style. I’ll have to take some pics, but I don’t think it resembles the style you are describing.

If the overflow tube attaches to the filler neck of the radiator just above the top tank, the system is designed to use a low pressure cap- - - -4-7 PSI, for instance. There will be a sealing surface below the overflow tube for the spring loaded cap gasket to seal against, and another (sometimes brass) seal above the overflow on the cap that keeps the coolant that gets past the cap from leaking out onto the tank instead of going down the tube. The actual zero pressure radiator has the overflow tube attached to a round canister on the back side of the top tank and a sealed cap without any springs.
Jerry

10-4. I’ll go hunt up a new radiator cap.

It’ll almost certainly be a Chinese one. They surely can’t screw up a radiator cap, right?

I was hired to testify as an "expert witness" in a suit against Auto Zone over a radiator cap. The cap they listed as a suitable replacement for a particular engine didn't fit, and allowed coolant to spill out onto the top tank of the radiator instead of going into the overflow reservoir. Then air was drawn into the radiator as the engine cooled down. Eventually the engine overheated and locked up from a gradual loss of coolant, because the vehicle owner was looking at the coolant level in the overflow tank and assuming the radiator was full. When the insurance adjuster reviewed my findings, the case was settled "out of court"- - - - -they didn't want me on the witness stand!
Jerry

I’m learning, bear with me.

So my truck likes to puke to a level that is below the top row of tubes. Sounds like I might be taking on air somewhere in the system. For what it’s worth I do have a 1/8 inch hole drilled in the thermostat. I understand now that might not be a bullet proof solution if the system is sucking air elsewhere.

It’s easy enough to replace the cap and check that off the list. Is it possible that small air leaks (that don’t produce visible leaks) could also contribute to the problem?

For instance, I know that my heater core has some sort of small leak. It can’t be more than a pinhole. I can smell it if the fan is turned on but have yet to find any moisture. Would it be with bypassing the heater core while I’m replacing the rad cap? I suppose it would also be good to tighten all hoses?

There is so much I want to say on this subject, but I am not going to...

As far as leak testing, go to your favorite FLAPS and rent/borrow a coolant system pressure tester. It lets you get the system to operating pressure without being hot so you can watch the gauge to see if there are leaks (pressure loss) and inspect the physical system for where the coolant is coming out.

Yes, even a tiny air leak can prevent a puke tank from functioning properly. Does your radiator have the overflow tube in the filler neck, or does it have the "tuna can" on the top tank? If it's got the overflow in the fill neck, try using a 4 pound pressure cap with the suction valve in the middle. That's the type that will be needed to siphon coolant back from the puke tank. Also, be sure the tubing at the puke tank is submerged in liquid so it can siphon properly. Yes, either fix the heater leak, or isolate it.
Jerry

10-4. Just for clarity:

1) The radiator does have the tube in the filler neck.

2) The puke tank does currently function to the extent that coolant goes in, and the radiator siphons it empty upon cooldown.

So much you want to say about cooling systems? Or so much to say about playing Russian roulette with questionable offshore parts?

You're losing coolant somewhere if the reservoir is being emptied on cooldown. Ideally, it should stay about half full and the radiator should stay entirely full- - - -no air at all in the top tank.
Jerry

Yes they can. Do not get one with a dimple on the top with the # poundage on it.
They will leak there. 2 out 3 did for me.

Yes, I’m definitely losing coolant out the overflow of the puke tank. But I presume that now to be a symptom not the cause. The cause being air in the system.

Is this the style cap you’re referring to?

https://www.oreillyauto.com/detail/...76/murray-4-psi-radiator-cap/mcs0/100205

Yes, that's the one- - - -the small disc at the bottom allows the vacuum in the cooling system as the engine cools down to siphon coolant back out of the puke tank. If the tank is too small, it will fill up and overflow. A couple of quarts should be plenty, with about a pint of liquid in the bottom, with a full radiator and a cold engine.
Jerry

Don't bet on it.

Here's the one on my truck. It holds about 2 or 3 pints when cold and rises another inch or so when hot.

Yes thats a version of the same rad cap. Some will not seal there at the top.
I`d get one with a flip lever or a sealed top.

Flip lever radiator caps are the spawn of the devil- - - -has anyone ever seen a pressure cooker with a flip lever on top? Imagine a pressure canner that holds 3 gallons of water, at a temperature above the boiling point, that suddenly gets the pressure released. That's the equivalent of lifting a radiator cap lever on a hot engine. If the coolant is hot enough to need pressure to keep it liquid, the only way to check or add coolant is to wait. When it's a cold engine, then open the cap. I'd recommend about a six pack's worth of time, at a minimum. Anything but Bud Light!
Jerry

The lever helps get air out initially. Then i`d take it off and
put a smooth top on. Like I said 2 out 3 failed on me with a tab on top.
They are cheap.

Why not just loosen the cap one notch to purge air during a fill? Backing off to the safety notch relieves the spring tension on the pressure valve as effectively as pulling that Rube Goldberg lever up.
Jerry

You are right. That would work. Point was to avoid these.

Nothing is as simple as I think. Not even radiator caps. I had some reward money about to expire so I ordered a “Murray 1002-05” 4 PSI cap from the O’Reilly. It arrived as a Motorad by the same part number.

Brought it home last night and it’s too “deep” to work. Can’t twist the cap shut because the pressure apparatus bottoms out before the tabs on the cap can reach the radiator flange and twist shut.

Anyone have a known modern part number for a 4 psi cap that works on a stock AD radiator? Poking around on RockAuto, I’m thinking that a Motorad T4 might fit.

My truck is out at my mom's house right now. I'll call her up and tell her to go look at the cap and see if there are any part numbers on it.

There are two standard heights of radiator fill necks that will cover probably 90% of every American made vehicle for about 50 years. Is there any reason someone can't use a tape measure or a ruler, measure the inside depth of the neck, go to the FLAPS, and do some measuring of the caps they have in stock? "This ain't rocket surgery!"- - - - -or maybe I'm having a Mr. Spock moment- - - -"That is not logical!" Getting OCD about specific part numbers doesn't make the cut in the real world of auto repair.

Jerry

Sorry JW, my mom just sent me pictures of the 4 lb cap on my truck but there isn't even a brand name on it let alone a part number.

It just says 4 lbs. and Warning Do Not Open Hot on the top. No numbers on the underside of it either.

What's to avoid? There are very few things on any motor vehicle that's as generic, or as neglected, as a radiator cap. When I managed a towing service and a repair shop on a major interstate intersection, I made it a point to pressure test the cap on everything that came into the shop, no matter what the original complaint was. I sold an average of 15 caps a week, due to the original one failing to hold the correct pressure.
Jerry