VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1937-1945 216 (1940) Spew after 2-3 minutes

Think I have read pretty much most of what has been posted.
Here are the current facts:

1) In final phases of sorting out a newly rebuilt original 216 for my 1940 MD. At my mechanics, and the following happened there, just as it did in my garage when first starting it up. No miles on the freshly rebuilt powertrain.
2) Starts and runs strong, great oil pressure.
3) After 2-3 minutes temp soars and spews out of overflow hose.
4) Complete new engine rebuilt, tanked, cleaned, etc.
5) Brand new 4 row all aluminum radiator by Superior Radiator in Mich.
6) Had a 165 therm in there and took it out, but same situation. Currently no thermostat.
7) Using a no pressure cap on that new radiator
8) Mechanic claimed that he saw a lot of air bubbles in the water spewing.
9) water pump is not leaking. Was rusty, I cleaned it thoroughly and refinished it. shaft seems fine, turns fine, etc.
10) Perfectly good stock fan.
11) All new hoses, stock 6 blade (?) fan.

So with a brand new motor we can skip the cleaning part. Is it that the motor is new, creating friction and needs to break in (that doesn't seem logical to me)? Is it the no-pressure cap? I think if I recall after my initial experience with this, I felt the top hose and it was real hot and bottom hose was cool. Should I put a 165 degree therm back in? Looking like it is the original water pump should I not be trusting it? It was completely cleaned, shaft seems fine and it is not leaking. Thanks in advance. I know 40's run hot but this should not be doing this obviously.

In filling the system originally it was done a little at a time. I am wondering if I still have a lot of air pockets. Engine has probably 15 minutes of run time over several sessions. I have also read a failed water pump seal will allow air to enter the intake or suction side of the pump. This produces bubbling when the trapped air reaches the radiator inlet neck.

I believe it is not the cap, thermostat or radiator.
Would suspect the head gasket. Pull the spark plugs and see if one (or two) have dfferent deposits than the others.

Thanks. I know after initial start-ups and the first time it overheated, I pulled them just to clean them before carb was finally adjusted,etc, and all the plugs looked the same..black but not fouled, not white-ish, not wet, etc. Man, it better not be a head gasket after the thorough rebuild it had.

Would using an infrared temperature sensor help to locate the hot spots?

The symptoms when running the engine point to the water pump. Does not appear to be circulating enough coolant within the block or through the radiator. If water is circulating without a thermostat then the lower hose should be cool to warm depending on the outside temperature. If the water is not circulating in the block the back cylinders will heat more than the front and when the water in the back begins to boil it will force a large volume of warm to hot water out of the radiator overflow.

If the water pump is sucking air that can reduce the liquid flow rate dramatically. It also puts air into the engine cooling passages that increases in volume as it heats up forcing liquid out of the of the cooling system.

Assuming the water pump is working....

Is it possible for the head gasket or water pump gasket to be installed incorrectly and blocking some coolant passageways?

Would a garden hose attached to the bottom hose inlet be one way of testing ease of flow to the top outlet?

The cold engine should be able to run two or three minutes with out overheating with the water pump not even turning.

And that would explain the air bubbles wouldn't it? Thanks. a few responses overall have pointed concern towards the radiator or head gasket. WIth both being brand new, I don't think so. The only thing not brand new is the water pump.

I had a brand new head gasket on a totally rebuilt engine fail almost immediately. The head gasket was a reproduction however.

I'm leaning towards the water pump. You should probably replace the water pump with a new unit, and if that does not cure your problem I would look seriously at the head gasket.

On a rebuilt engine I always install a new water pump and a new oil pump. Not doing so is asking for trouble.

SO both were installed correctly as I took pictures of everything. Thanks.

And yes it does.

Yes it has a new oil pump.

OK so in talking to an expert that has been working these specific Chevy motors for years, and is also a smaller but popular vendor for our stuff, he instructed as follows. He says he sees this problem a lot. He did not think it is the pump.
Note...I will do a compression check to make sure head gasket is not the issue but assuming it is not:

1) In refilling the engine with 50/50 coolant often times if you do not open up the port in the back of the cyl head where you water temp sensor bushing is, it creates an air trap. So that will be done. I did not do it that way initially:

2) He highly recommends a 180 degree thermostat. I had a new faulty 165 and trashed it but as mentioned with or without it acted the same way.

3) He highly recommends a 4-7 lb cap. Not a no pressure cap.

4) For the purpose of coolant recovery, put in the tank but that is not critical.

All that said it still could be items that you guys (and my own inklings) are suggesting. I will start with these.

I have never had an "air trap" problem with a 216.
I have filled them with straight water with no problem.
I have used no thermmostat or a 160 Deg. with no problem.
A preaaure cap was not used (and filler neck not designed to use one) until 1948 and that posed no problem.
A compression test will not pin point the leak.

These engines are very simple and straight forward.....you have a large problem some where and most likely will have to remove the head to find it.

I might suggest a "leak down test" of each cylinder to find if a bad head gasket is the culprit...Sounds as though it is the case...Checking each spark plug for any difference in discoloration is a clue...Bubbles in your coolant is a dead give away also...Didn't mention if you used any sealant on the gasket...That's a no-no...Good Luck

Forgot to ask if you had the head "magnetic particle tested..." A head crack could cause concern...

Might even want to check the torque on all the head bolts one more time, also...Never know...

Sorry for interupting the recent brake cylinder thread...

All your suggestions are duly noted. And they will be addressed as needed.
I have had air trap problems before on several other Chevy motors from 235 to 396.
Yes I can do leak down testing. I believe the problem is in the cooling system itself. The exhaust which with a blown head gasket will show white-ish color and moisture. None of that is happening either.
No, sealant was not used on the head gasket.

I will certainly delve into H'gasket if this doe not work.

By the way at this point the DIY scenario has ceased. The car is in the good hands of D&B Automotive in Solana Beach where they are doing several things to the car such as testing the vacuum assist shift canister which tested fine, clutch adjust, etc.

You are right, these motors are straightforward. During this entire project it seems every time I experienced a problem and delved deep, it turned out to be a simple thing.
Thanks again and will report back for future reference once this is sorted.

One thought that you may want to investigate. When I had my '38 216 rebuilt it too was hot tanked. That didn't flush all of the crud out of the passageways that had been loosened though. I ended up with overheating issues because my radiator filled up with the rusty mud that the hot tank loosened but was still in the engine. I ended up having to pull the radiator & thoroughly flush the engine. My point being that just because someone told you they flushed the engine after the tank job doesn't mean they did it correctly and thoroughly. You may have a blocked passageway.

Just a thought. A while back their was a post just like yours. In that thread it turned out that they had used a one piece bottom rad. hose without the internal spring and the hose was collapsing and restricting water flow.

if either hose is cold you are not circulateing water.
if water pump is good you are clogged.
i cleaned out a 207 last year,it was so rusted in the water ports
i had to take a small steel rod and poke the wedged rust in the
water ports so it would come out.i even had to turn the engine on it's side back and forth to keep the flat peices of rust from jaming up again and again.when i got done i had a half a 5 gallon bucket full of solid peices of rust.this engine was supposedly just boiled and flushed.in my opinion you have clogged water ports,also your water looked really rusty.
the only other thing i have run into to make an engine run hot is being out of time.
i would say the majority of these old engines are half clogged with rust thats why almost everybody boils over in a parade on a hot day.if your cooling system is in good shape these engines should not boil over at all.

Note that he mentioned that it has a brand new 4 row radiator. I don't think it would have plugged-up that soon.

"On a rebuilt engine I always install a new water pump and a new oil pump. Not doing so is asking for trouble".

Could not agree more !

Why no new water pump on a fresh rebuild ???

Hey! That's exactly what my doctor said to me the other day!!

So again gents thanks much for all your comments. Very helpful in general. Let me put closure to the topic. The one thing I got hung up on was the fact that the stock radiator had the zero pressure cap. Well, I don't have a stock radiator. I have a new alum one. Guess what? It demands a pressure cap. How ignorant of me. So the engine was not really overheating as such however because the radiator did not see any pressure it expanded under heat I guess and spewed out the coolant. I put a 13 lb pressure cap (could have been a 7 for that matter) and engine and all temps run perfectly fine. No blown gasket, no clogged engine just a new clean motor cruising at 15 lbs of oil pressure and 185 degrees of H20 temp with 120 to 130 lbs compression on this 75 degree day here in Socal. I felt it was something with the cooling system as I have used this very competent engine builder in the past and he rarely makes errors in building them.
Again thanks and hope this helps others if they get a new radiator. The small Chevy parts vendor that I referred to in the OP talked about the 185 thermo stat, and the potential air pocket in the head, and mentioned the pressure cap as well.