The Stovebolt Site Forums The Shop Area Engine Shop 235 troubles

This is a fairly long post and explanation. Any good mechanics...please take the time to read - I REALLY need your expertise and experiences. I
have two days before I have to get this on the road for a 10 hour trip, and am running out of time. As much as I hate to even think about it, if I can't get this solved, I am seriously thinking about selling the truck. I just spent almost $900 to rebuild the new engine, and am now where closer to fixing it than before. I can't afford to keep throwing money at a problem
that doesn't seem to me to be solvable.

Well, I am absolutely and totally at a loss as to what is wrong. During the breakin, I followed the advice I've always heard as to how to break in an engine, ie. to run it up to around 2000 rpms, and let it sit there for 15-20 minutes. So I did that. Everything seemed to go pretty normal. The temp gradually got up to 190 or so (no thermostat yet installed), and held there.
I didn't see any small bubbles during this time and just before the end of the 20 minutes, I put the radiator cap on. BUT, as I reached the end of the break in, and as I reduced the rpms to idle, all of a sudden the water from the radiator started spewing (with sufficient force to shoot to the fender)out under pressure out of the overflow tube at the filler neck (cap is a
zero pressure cap). I immediately shut down the engine, and looked inside the radiator and saw nothing of concern. I started the engine again and gradually added water so it wouldn't be hit with a large volume of cold water at once. That went fine, but at idle, I am seeing the same darn small bubbles!

As some may recall, I originally rebuilt the 235 because of bubbles in the radiator and pressure getting into the water system (I had a thermostat
installed and when it hit opening temperature, a rush of water and air caused the radiator to volcano. I had originally suspected a blown head
gasket was allowing air to enter the system, causing it to not only overheat, but was the source of the air getting into the system which, when the thermostat opened, allowed this air to rapidly escape and cause the volcano effect. So I put on a new head gasket, but the same problem was there. So, suspecting I may have messed up the head gasket somehow when I put on the head (I did it myself and thought I might have somehow scored the gasket while setting the head on), I tried again with a new head gasket, but before that, I took the head and had it magnafluxed and surfaced...but after putting on the head and new gasket...same thing, same bubbles and air getting into the water jacket. So, suspecting a cracked head (as 235 heads are prone to do) and that was missed by the machine shop, I found a replacement engine (thanks again Skip) to use the head. I took that head and had it pressure tested and the surface checked...it checked out ok. So, now the third new gasket went on with the second head. Same problem. That pretty much, at least in my mind, left only the block as being the cause....so out with the engine, and I began rebuilding the engine I got with the replacement head.

The "new" block was able to be bored to .040...I also had the crank turned to .010. Anyway, I put in new pistons, bearings, timing set, cam, lifters, and everything was within specs. I mic'd everything, and also used plastigauge to be sure. All clearances (bearing and rings) were perfect.

So, I don't think anything was wrong with the machine work. I am getting good compression on all cylinders and all within acceptable range.

So, I have now rebuilt the engine with new everything at least internally, and am still at the same point I was at in the beginning, ie. with small bubbles getting into the water system, and judging by the way the water shot out when I dropped the RPMs after the breakin, I suspect the system is building up pressure somehow. The water pump is the original pump, and all hoses are the ones from the old engine.

I have to believe my rebuild was done accurately. I followed torque specs to the letter, and torqued the head following the torque pattern in the manual, and did it in 3 stages. I took my time and was always careful and
thorough. The last time I rebuilt a 235, it was able to do two crosscountry trips and all was good (until this saga with the bubbles and overheating began), and have never had any other engine rebuild go bad. I consider myself a pretty good mechanic, and follow the manual to the letter. This problem has me totally stumped.

Assuming then that all the machine work was done correctly (block boring and head checking), and my rebuild done correctly, where else might air be
entering the system? Could it be coming in from the water pump even though the pump is showing no signs of an external leak? Could it be coming in one of the hoses and not show any external signs of a leak?

The system is a zero pressure system...so, my thinking is that maybe somehow air is able to be sucked into the system, but since the system itself doesn't build up pressure, it is not "squeezing" water to the outside...just
sucking air. Does this make any sense to anyone? If so, how do I determine what is behind this if not the head or head gasket? Can the system be pressurized to see if the reverse occurs, in other words, if air can get into the water jacket, if the system is pressurized, could it cause water to follow the air path?

ANY thoughts are VERY much appreciated. If anyone wants to discuss this in person, my phone number (cell) is 360-551-2490.

Thanks for your patience with this long post and in advance for any help you can offer.

P.S. I am thinking of going ahead and replacing the water pump and all hoses, but know I need a shortshaft water pump, which is not generally
available at the local auto parts but has to be ordered from one of the truck vendors, but unfortuantely, I don't have time now to wait for it to be shipped. SO....if I buy a long shaft at one of the local stores, can't I simply have the plate that the fan and pulley mount to, pressed down the shaft and then have the excess cut off? If so, as I suspect I can, can anyone tell me how far down to have the plate pressed (ie. when to stop so that the pulley would line up).

Rob

I would get that thing broken in and drive it as much as possible. Then do a leak down test to determine if there is actualy a leak. Does it bubble when cold?

It sounds like the water pump is sucking air. I would take the old water pump and measure it to determine how much to cut off the shaft and also make sure there isn't anything else that will keep you from using the "long shaft" water pump after the shaft is cut off.
I have never heard of a 235 giving any one that much trouble. They are one of the easiest engines to overhaul.

I don't claim to be an expert on 235 rebuilds but I do have alot of experience trouble shooting diesels and except for fuel systems vs carburation, it's the same. Sounds at first as tho you had a head gasket problem or cracked head but you eliminated that problem and the block as well as the source of compression in the coolant. For the sake of not missing the obvious(which in my experience is almost 80-90% the cause of these tricky little conumdrums), the only other sources are the radiator, water pump and heater core. Is it possible the problem is the thermosat? Have you replaced it or checked the old one to see if it's working properly?

As I am too technically deficient (read lazy) please read my response in the lounge.

Take the truck to any good shop and have them pressure test the system, cost about $20-30. The tester is about $100 to buy off a tool truck. If there is a leak it should show up most systems are safe to pressurize to about 15 PSI. Anything that can suck air should push water out also.
Good Luck
Brad

I would suspect the radiator. I have an '83 250 that overheated for years and we would look in the radiator and see water circuilating as expected. After replacing everything else, I pulled the radiator and removed the end tank. The radiator was completely plugged over half its height. I had less that 50% of a small 2 row radiator function. Replaced radiator with HD 4 row and have had no problems for last 5 years.