The Stovebolt Site Forums The Shop Area Engine Shop 235 keeps boiling over - help!

I can't keep this engine from boiling over while I adjust it in my garage to save my life! I even took the 160 degree thermostat out and am running it without now. The 1941 truck has a new aluminum radiator and the fan can only go on the engine one way so it isn't backwards. I've tried different timing settings to no avail. Also I've been careful to not refill the radiator more than enough to cover the tubes so it isn't overfilled.

The water pump is still the one that came with the engine, and the engine could still have some sediment in it clogging up the coolant passages (I've put two bottles of flush in it so far in case this is the problem). Those are the only two things I can think of causing the problem.

Any other ideas?

What year is the 235?

Are you running a pressurized radiator cap? I'm breaking in my 61-261 on a skid and jury rigged a cross flow radiator with a 0 pressure cap and it boiled over with both a 160 and 180 stat. Put on a 7 psi radiator cap and the boiling over went away.

It's a '56 model engine from what I can tell. I don't know if it's pressurized or not. It's one of the reproduction caps.

Pressurized caps have a spring holding the sealling surface to the radiator fill neck. When the pressure is exceeded the spring loaded sealling surface is pushed off of the filler neck releasing pressure.

If there isn't a spring it's a vented (zero pressure) cap.

Mike B

Dave will let you know if the orientation of the newer engine's fan blade to the radiator is satisfactory.

I have found that these engines accumulate significant sediment at the rear of the block. It is not easy to clear this area with engine flush. I have had to use a heavy gauge copper wire and dig at the blockage from the drain hole at the lower manifold part of the block and dig at the blockage from the water pump hole at the front of the block (working on the left-interior and right interior towards to rear). These later engines (engine-blocks) have a much larger water pump opening than the holes on the older blocks.

Using a pressure washer from both locations makes this an even messy-er job, but it helps a lot.

If you use a pressurized cap, watch your heater for leaks (presumably, your aluminum radiator is made for pressure - your original radiator was not).

What are you using for a water pump? A short shaft?
Is your timing advanced enough?

Might have a thought. We did a 57 1/2 ton truck with a 235. Pulled the radiator to change the front seal. Put it all back together and it got hot! Turns out that we trapped a huge air bubble in there and air won't cool anything. After the bubble came around and the steam blew past us we had to add lots more coolant. Next time we ran the truck with the cap off. Same issue. Just getting that air out was a pain. after it passed the bubble...no more issues. Any one got a trick for this?

How long does it run before it starts to boil the coolant? Is there a temp gauge hooked up and working? What does it say?

Is this a rebuilt engine, or just firing one up?

If it's an older engine perhaps the coolant passages are blocked from sediment.

To start with if its a hot climate and you run without a thermostat it is going to over heat. Why? Because the coolant is just continously circulating, it doen't get a chance to slow down and get cooled off.
If its a cold climate then it will over cool, as it passes through a constantly frozen radiator and never gets a chance to warm up. May not make sense, just try it and you'll see.

If its clean and has good flow, the pump is working etc. then like others mentioned timing, and lean fuel mixture will do it too.
Did you trouble shoot it? Check outlet temps and inlet temp, check temp across the radiator etc. Is there good airflow through the radiator?
I would put in a "checked" 180 thermostat, don't run with out it.

To answer Steve H's question, drill a 1/8" hole in the thermostat. That will allow the air to escape as the system fills.

Some people prop the thermostat open with an aspirin when doing first fill, but I'd be afraid I'd screw up the thermostat and poke a hole in my hand at the same time.

Where on the thermostat do you drill the hole?

Where it will vent when the stat is closed. Is this a new engine you installed?

I tried to bleed the air out by loosening the temp gauge fitting while the engine was running and then tightening it back up when coolant started to come out earlier when I was trying to run it.

To answer some previous questions: yes, we have a rebuilt temp gauge that is hooked up, and we have what I believe is a short water pump which is what the engine had on it when it was purchased. The engine was running when I got it from someone who took it out of a truck of some sort (but I think it was originally in a car) - I heard it run - but it wasn't connected to any kind of a cooling system. Now it overheats within about five minutes.

I don't know what is meant by advanced or retarded timing on these engines because there are no timing marks. Does advancing the timing mean turning the distributor clockwise and retarding the timing mean turning it counterclockwise? I tried to set the timing so the ball on the flywheel lines up with the pointer on the round hole in the bellhousing.

The cooling fan I have fits on the water pump one way, so there isn't a way to get this backwards. On this truck the blades barely clear the radiator's outlet and are about 1/2" from the fins.

My 43 GMC had a weird habit of spitting out coolant via the radiator cap (down through the over flow tube.). Turns out that the cap needs a gasket to seal properly. $1 item must have cost me 3 gallons of anti freeze.

Other thing I learned is that of the three 40's vehicles I have (42 Ford, 43 GMC, 43 Chevvy) all of them have a different coolant level that they like... and none of them are anywhere near what the book says it should be.

One thing that did help IMMENSELY for the Ford was adding in the felt grill/radiator baffles. At speed most of the air was going AROUND the radiator because the baffles were not installed. So make sure you have all the sheet metal in place and if there is a fan shroud make sure its in good shape.

...click...

The last thermostat I purchased had a built in air check valve
...click...
Mr gasket 4364 180 degrees

Is it boiling over or just expanding. I second it, leave the thermostat in, (but make sure it is a good one) If it is below boiling, you should be able to get away with a zero pressure cap. I drove my truck around for about a year with basically no cap at all, I had one that kind of fit, but it mostly just kept the water from splashing out, and I was using a 195 degree thermostat. What is the temperature anyway?

I started out with a 195 degree thermostat, then switched to a 160 degree one.

I took the rear drain out and poked around thru the hole with a #12 bare copper wire; I broke something loose because all of a sudden a bunch of trapped rust colored coolant gushed out. When I poke around now and pull the wire out it is covered with black gunk. I think tomorrow I'm going to push the truck outside and try to flush out the engine cooling passages with the garden hose.

What path does the coolant actually take as it goes thru the engine?

The path of least resistance/blockage (no joke).

In general, into the block and out the head: 1941 - same direction in later 235/261 engines.

I was just wondering if it was completely hollow around the cylinder walls or if there are several individual water jackets that the coolant has to be able to go thru. In other words I'm trying to figure out where I need to try to get the crud out of and how to go about getting in there.

without tearing into the engine, the way tim has mentioned on an earlier post is about the best you can do. just keep filling, rodding, draining and flushing. ride it aroud with just water for a while and see what it does.

crud in the block shouldn't make the water hot, it would actually tend to prevent heat transfer to the water, causing higher cylinder temperatures because it isn't making it to the water. unless it is absolutely packed so solid you aren't getting any circulation at all. You mentioned you TRIED to set the timing on the ball, no mention of whether or not you were successful. Did you ever get the timing set correctly? are you sure you aren't bypassing something somewhere in your setup, sounds more like a circulation problem to me. Not to say you shouldn't clean the coolant passages in the block though. I may have missed it, but what type of temperatures are we talking about? The thermostat has no bearing on the upper levels of temperature as long as it is operating properly, it just keeps the temp at a minimum setting. Do you know if this engine ever ran correctly? Is there any way to talk to the fella you got it from? Ask him if he had changed anything? Does the head gasket have all the holes in the right spots, is there even an impeller on the water pump, things like that.

A really good way to back flush the block is with a power washer or car wash wand right in the drain hole. Blow in with pressure, use garden hose at thermostat hole to flush out crude. Do this a bunch of times till block runs clean. Same applies to radiator only don't use power washer! I have flushed them using radiator cleaner and just hot water. Lay the radiator face up on the floor and fill with hot water and cleaner, let set a while and flush it out.

Joe

The problem with the 'use water pressure' method is that as you loosened the crud, it will find new, smaller holes (in the head, most likely) to clog.

Your issue isn't in the block. Its in the radiator/thermostat/water pump.

Its the radiators job to move the heat from the water to the air. That's clearly not happening.

Is the radiator the size (as in BTU rating, not just dimension) as the old? Did you think 'it aluminum, I can use a smaller core'?.

Is it the same number of rows?

You NEED a radiator cap. Won't even get into that.

Are all the baffles/shrouds installed?

Your dirty block is a separate issue.

This is what I am talking about (thirst post)

http://www.jalopyjournal.com/forum/showthread.php?t=340935

The radiator I got was an aluminum "universal streetrod radiator" from Summit that was the same dimensions (give or take a fraction) as the original. The reason I got this radiator was because the owner of this truck was too cheap to get a "reproduction" radiator or have his old one re-cored. I figured it should have plenty of cooling capacity because most people that build streetrods put big V-8 engines in them with air conditioning and automatic transmissions.

The guy I bought the engine from ran it for me and it ran fine. He didn't make any changes to it that I can see. It apparently didn't have any coolant in it (other than what was trapped in it) when he ran it for me. I have tried repeatedly to contact this guy but he won't answer or return my calls.

It pretty much hollow around the cylinder walls. The rear drain port is pretty important to get free of crud. Once you have water coming nicely out of that port, with a good thermostat in, and I differ from others in that I always put in a 7 pound cap on the radiator. 7 pounds is almost nothing in the scheme of things but puts enough back pressure on the system to give it positive cooling flow. Its really a matter of your experiences one way or the other. If things are really bad, you can always remove the freeze plugs making sure you have a source for new ones, but at that point I would think its time for an engine rebuild.

Re the question about the temp. and timing: The temp. gauge needle goes all the way to the right when it boils over so I'm guessing the engine is running at over 220 degrees. This happens very quickly so I shut it down immediately when it starts to go this high. I have a fan on the front of the truck to provide air circulation.

Most of the front clip is off of the truck so no baffles are in place. If I had the clip on I wouldn't be able to get at what I need to very easily to work on it. Also, the fenders were painted not too long ago so I don't want them messed up.

The ball is pretty close to the center of the window in the bellhousing (I can see it wobbling around), but to be honest the engine overheats so fast I don't have much time to adjust the timing once the engine warms up so It's been hard to get it perfect. Once the engine overheats I have to let it cool back down which takes a while before I can take another stab at it. Very frustrating!

I did some block cleaning with my wire and flushing with the garden hose. I did this for an hour alternating between the two, and I probably could have done it for another hour and got stuff to come out. I finally quit and put a new Gates 180 degree thermostat in. I'm trying to decide whether to put another bottle of flush in to try to get at what's left in the block.

If this helps any, I have my 261 on an engine stand with nothing around it at all. The only thing that matters is the 1/2 inch or so clearance between the fan and the radiator. When I run it, I get a perfect 180 degrees max. (7 pound cap) So I feel you can eliminate any worries about sheet metal interference. You have a known good radiator right? The water pump is good? The thermostat isn't in backwards? Sorry, but trying for the simple.

all the pressure cap does is increase the boiling point. Even if the fan was on backwards it would still cool just sitting in the garage. For some reason you aren't getting flow, just figure out why, I would take the water pump off and look in there. As that is what creates the flow. Is there water flowing through the radiator? You should be able to see some movement.

Try this, unhook the heater hoses and feed the water pump heater hose inlet with the garden hose. Let the other outlet dump out on the ground. Adjust the water flow so the engine maintains temperature while adjusting the timing and carb. You need to eliminate a few of the variables before moving forward.

Joe

I need to check the flow. It probably wouldn't hurt to just get a new water pump anyway because this one is pretty old and rusty. For all I know it's the original one.

I worked on the timing again this evening until it started to boil over.

Did you check the inlet and outlet temps? Did you put the thermostat back in?

yes, pull the water pump, you can't just keep boiling it over, over, and over. and doing the same thing over and over. (they keep doing that at work, drives me insane)

Something is keeping the water in the engine and not allowing it to circulate. Pulling the water pump will let you see inside the block, take off the thermostat housing and you will be able to see inside the head, maybe the rather smallish passage on the outlet of the head is blocked with rust.

Make sure the thermostat works, just being new is no guarantee. Actually in this day and age, being new is probably bad... If it overheats it won't be because you have a thermostat in it, unless like the other fella said, is it in backwards? Why don't you try turning it around, the worst you could do is boil it over. Most of them say "towards radiator", if not, the little temp sensing element goes toward the head.

drill your little hole in the thermost to let air out.

But at this point you are going to have to go deeper, did you even take out the temp sensing element for the gauge out? That way you can look inside the head for issues as well. Have you tried another temp gauge? Get an infared/laser thermometer and check temps in various spots on the engine.

Maybe I missed something earlier in the thread, but have you checked for a bad head gasket?

I don't think its a flow issue. The time it would take for the stationary water in the block to convectivly heat the water in the radiator to the boiling point would damage the motor.

Plus to verify flow all you have to do is feel the radiator hoses as you watch the gauge.

Since the only thing that appears to have changed is the radiator to look elsewhere seems pointless. Is the radiator the proper number of rows and the same flow pattern (top to bottom) as the old?

I think the second paragraph is a MAJOR clue.

Yes, this engine ended up being a real lemon. I guess you never know with a used engine.

I don't understand what is meant by inlet and outlet temperatures. Is that of the engine or the radiator? I would assume that if water and steam is spewing out of the radiator overflow everything is at least 212 degrees.

The water temp. gauge is newly rebuilt - and it cost a fortune to do it - so it better be working right.

Water pumps for these engines are well over $100 new and nearly that much reman. so I don't want to have to replace this if I don't have to.

Rockauto.com
1956 CHEVROLET TRUCK 3.8L 235cid L6 :
Cooling System : Water Pump Price: $37.79
CARDONE SELECT Part # 5511132
{#PWP208} New; Includes Gasket

Or, your older style pump (with relocation plate) for about $65 form Rockauto.com or $70 from NAPA

Second part first: The "assuming" is what screws you every time... Get an HF infrared temp sensor (Tell her it's so the kitchen skillet oil doesn't get to hot and get unhealthy...) and then you'll Know there's a difference and what it is.

First part second: Water/Heat travels In at the Rad top from the engine 'top' (heat rises), after 'filtering' the heat out as it travels down the radiator the H2O goes back from rad bottom to engine bottom.

One question I didn't quite understand from page three... Did the rad come with the truck or did you buy it?