VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1929-1932 overheating 31

Hi guys I am out of my league with this problem ,a good friend of mine has a newly restored 31 that has just developed a boiling /overheating problem ,it dumps the water out of the overflow ,as everything is new ie: reco motor ,new honeycombe radiator .we thought that possibly has cracked the head or blown the head gasket ,NO on both counts ,then we noticed that the water passage holes in the block has had the first two holes 3/4" pluged up with what looks like devcon and then we noticed the large hole between the 1st and 2nd cylinder was reduced in size the same way and then the large hole in the centre of the block was also reduced as well as the last hole at the rear .It has been done very professional and hard to detect ,another friend told us that this may have been done to send more water flow to the rear of the motor. I saw this motor when it was sent to the reco shop and all of these mod's were there then ,so we are thinking that maybe it was done some time back .As he imported this car from the states ,has anyone heard of this befor ? also we noticed that the cylinder head was also a later manufactured head it has the bowtie then 4 with the number 836961 then in the middle of the head is CONV 12 and then the casting date is B 10 7 ,I alway thought that the later six cyl motors were bigger and the heads would not interchange is that right? any ideas. there is not a lot of 31,s here to look at .

Casting number 836961 is a cylinder head for a 1933 series CA Master. The head was cast on February 10th, 1937. The 1933 cylinder head will fit on a 1931 since the head gasket is the same from 1929 thru 1933 except for the 1933 standard models.

:) :grin:

Thanks Skip that sheds some light on our problem, was it common to recast these heads years later? Jim

For replacement parts the casting date would be the later date on which the head was cast. Could be a date 10 years newer than the actual car. In your case the head was from a 1933 Chevrolet (new or replacement) as a new head for a 1931 was still available but....Thats was probably the first head they found laying around when the '31 needed a different head.
Have you removed the water pump to see if ths baffle behind it is still in place? and inspected the water pump.

Yes Gene a new baffel was installed when the motor was reconditioned as well as the waterpump. this car is a fresh resto and I kid you not when I say the owner spared no expence. The cars first trip was trouble free ( appros 250 miles) and then the first indication of the water dumping and the car boiling started on its third outing,checked timing ,thermostat,compression all the obvious so we decided to remove the head while we we inspecting the block we notice that some of the water holes passing through to the head were modified ,as we don,t have any 31's close buy to look at we thought that maybe some one on the chat site my know of this modification if not then I guess we will drill the blocked holes out to match the head and gasket ???

Jim,
If your head and block have been hot tank cleaned , some of
the loosened scale may have come loose with water pressure flowing through the block, and then blocked off your radiator
passages, Give the radiator a reverse flush, and then see if your temp comes back to normal.
I can email some pictures of a 31 block and head if needed.

Also check the water pump packing. To make sure it's not sucking air. That will cause foaming and throwing out water and oveheating.

Remove the thermostat and see if that helps.

:) :grin:

Jack yes the block and head were hot tanked and they still look clean no scale to speek off but some discoloration,and the radiator has been reversed flushed,
Cleon I check into the water punp it had no leaks but I do realise that that doesn't meen that it won't suck air.
Skip the first thing was to remove the thermostat we even tried a different temp range still dumped water?
What my thoughts are is with those water passage holes blocked off that maybe there is an air pocket in the block ? so I think we will try drilling them out even if they are reduced ,this may still let the water flow and possibly remove any air pockets.
Jack if you could possibly send me a photo of the top of the block that might help a lot to get us back to what we should have.

Hi Jim,

If this condition took place at a specific time, reason says it is either a blown headgasket or a cracked head.

I would point the responsibility to the head.

If still off, I would have it pressure tested and magnafluxed.

If you had, or could borrow, another head for a test run it would be worth setting up for the test.

You might also contact a good radiator shop to have the chemical added to the water that detects exhaust.

i bought a small, cheap kit to test for exhaust gases in coolant. came off the local Snap-On truck. works well. mike

Ray the head is in beeing checked now presure test and magnafluxed should be back on saturday.
mike we will wait and see what happens on Saturday but I will look into that ,snap on trucks are all over here , thanks guys

I just got some photo's from jack39rdstr and his 31 block is the same in all the water passage holes as my friends ,so that is a releif where I thought that the water passage holes were moderfied it appears that is is how 31's are? thanks again Jack

Jim,
The later 6 cylinders are the same...some of the water passages in the head are not the same size/location as the holes in the block. When I removed my head on the '35 I found rust blocking several of the smaller holes in the block.
You didn't mention but after 250 miles was the head re-torqued? The head gasket will compress a bit and the bolts should be tightened. If not the head gasket can leak or fail. Have you done a compression test? All cylinders should have compression ratings that are close to one another.
Keep us posted on your progress.

Hello Jim,

Just to tell you about my experiences:
My 31 has the original fan with 2 blades, and last summer when I bought the car, it got really hot when I was in town (Salzburg) during rush hour with only stop and go drive. It got red at the dash indicator all the time, but, scared of this, I took a digital cooking gauge from my kitchen and I did see, it reaches never boiling temperature. The indicator (as it is called) is just an indicator about cool or hot, it says nothing about the absolute temperature.
But, after switching off the engine for ex. at gasoline station, I could not start anymore, because the heat of the motor got the fuel in the gasoline-pump boiling and I had to cool down the fuel pump with cold water to be able to start again. Had always a bottle of cold water with me for emergenzy use...Later I did flush the radiator and did fill in a chemical cleaner like to clean a coffee-machine, you understand? Sorry, english is not my native language and often I dont find the correct terms.

After running the engine at idle speed but covering the radiator to bring it to boiling point the chemicals did work and a really awful dirty rusty mess came out when flushing out the boiling water...Did it two times and did flush the complete system with cold water later and now the engine gets less hot. My Chevy comes from africa and has no thermostat at all.

Now I use a special anti-freeze (yes, winter is coming) and this helps too to protect the whole cooling system. What all buddies here say would I do as well: Check the water pump!

If i would have the problem, I would do a test: Remove the hose coming from down of the radiator to pump, instead of this install a hose in a bucket of water, and remove the upper hose as well and check if the pump sucks and spits lots of water when engine is running. Easiest way to find out wether the pump works or not.

The 31 have an opened cooling system, so it is normal, that if you fill in water to full level when engine is off and cool it will flow over when it gets hot. After shutting off and cooling down you will have the imagination oh, I have to fill up, and if you do, it will overflow again. Just normal...

Wish you good luck
Stefan

Jim,
Several things are common with those none pressurized systems. First filling the radiator more than just above the core will result in loss of the extra coolant as it heats up, expands and is expelled out the overflow tube. Second it is common for air to be drawn in past the shaft on the water pump even when no water leaks in that area. A telltale sign of air is when the engine speed is reduced (like at a stop sign) it fairly quickly spits out water. The total explaination is a bit long but basically the air bubbles expand inside the engine forcing water from the radiator. Third unless you allow the engine to run a few minutes after running at speed, pulling a upgrade or other condition where the engine produces a bunch of heat the excess heat in the engine will increase the temperature (and maybe even reach boiling temperature) inside the cooling passages. The back of the block/head near the firewall gets the hottest as it gets less cooling when the engine is not running. That higher temperature will force out more coolant. If boiling the vapor created will push out even more. This normally takes a longer time to pushout the coolant than air.

Thanks guys for your thoughts.lots of good things to check over I did check compression and it was fine , the tension was fine,and we are aware about overfilling the radiator I have been driving my 28 for 24 years now and brian who ownes the 31 isn't far behind me . These thing are frustrating but with your help we will fix them I have also had a number of private emails suggesting various thing as well so My next question now is the waterpump baffel plate HOW TIGHT SHOUD IT BE IN THE BLOCK. and the other question is WHAT MEASUREMENT SHOULD IT BE FROM THE FRONT OF THE BLOCK and WHICH WAY SHOULD IT GO IN, FLANGE IN OR FLANGE OUT .This way we hopefully can eliminate one thing at a time .some time this week end we wil get the head back and know more about it's condition.

On a '31 the baffle plate is 1" from the machined surface. Just enough so the impeller does not touch it but close enough so it makes a close fit.

Jim.
The baffle plate in my block feels to be flanged side into the
block, which gives a flat surface out for the water pump impeller to seal against.

thanks Chip and jack ,the head was picked up thismorning and it is all ok ,so we will reassemble the top end and have another go .I have received a few emails re the baffel plate hence the questions it was new ,however it is installed and removed by hand (no Tools required) and and from what we have been told it should be a interferance fit .

Yes, the baffle plate should be pressed into place, it should not slip in by hand. If it is loose it can cause overheating.

:) :grin:

This discussion of the baffle plate is very interesting to me. Back in the 70's, I bought a 31 five-window coupe from a farmer in Colorado. It had been left out in the weather for a while, and the roof insert was essentially gone, but all-in-all, the car was in pretty good shape. I lived in northern New Mexico and put quite a few miles on the car. It ran fine, and around town and on relatively flat terrain on the highway, the engine temp remained near normal. However, whenever I attempted a long uphill pull, the cooling system would overheat. The original radiator was in great shape, and I took the water pump out to inspect it, finding it to be in good condition also. I remember looking into the pump cavity in the block and thinking there should be some kind of housing around the impeller, otherwise it would just be spinning and churning the water--not pumping it. But, there was no baffle in there, and no reference to it in my 31 shop manual, so I put it back together, thinking the designers were smarter than I am, so there must be some other problem. I had the car for two or three years, then sold it and moved on to a 39 pickup, then a 33 sport coupe, and now a 40 pickup. Well, having read this discussion about the baffle plate, some 35 years later, it's now clear that my overheating problem was due to the missing baffle plate. I wonder what happened to it. Were the originals steel? If so, I guess it probably just rusted away and ended up as red mud in the bottom of the radiator. Having instantaneous access to the huge pool of expertise and experience that this discussion forum and the VCCA provides is certainly a great improvement to the hobby.

Mark Yeamans
VCCA #35724

Two types of baffle plates were used......steel and brass.

:) :grin:

Brian has reassembled the motor this weekend and I resized the Baffel plate today the flange was 0.020" smaller than the bore ,also made a new drift tool to tap the baffel into is seat at 1" from the front flange . all going well should be able to fire it up tomorrow and see what happens???

Well everything is reassembled and seems to be running fine,we think that our problem was the baffel plate and now it has run for several hours and not even looking like getting hot .I guess that some repo parts arn't all that they are suppost to be ???? even though it was new it didn't fit and more important it didn't work .