The Stovebolt Site Forums The Shop Area Engine Shop Overheating after replacing fan belt

On Tuesday morning my fan belt broke when I stated up the truck, luckily I had a new one just in case so I changed it out. Well yesterday on the way home from work I smell antifreeze while sitting at a stop light looked down and the gauge was up near 212. I stopped and opened up the heater valve I have under the hood and drove home with the heater on. It would creep down to normal as long as I was running over 45mph but as soon as I slowed down it start going back up. Didn't have much time last night to look into it because of other obligations but I did check and tighten the fan belt a little but when I ran it again the same thing happened. With the fan belt breaking and then this happening I'm thinking water pump, but I'm also going to check the thermostat (160 now) and radiator to see if it's plugged. Is there anything else I should check? This engine was rebuilt back in 90 or 91 and driven until 95 then parked until April '13 when I restated it. I had flushed the radiator and engine then but I guess it's possible some rust may have come loose in the 3500 miles I've driven since then. This is a 55 235 but it looks like it has the older water pump on it and the fan sits low but I've never had this issue before.

If the belt is the correct size (width) for the pulleys and you tightened it properly, the belt cannot be the cause of the problem. Start the engine and check to see if the fan and hence the water pump is spinning. If the fan is not moving or barely spinning, then I suppose the water pump bearings are locking up or are locked up. The resultant slippage of the belt on the pulley would have caused your initial belt break.

If it all looks normal after visual inspection, then use an infrared thermometer and compare radiator inlet temp vs outlet temp. If you get a large variance (not sure what, but maybe more than 20-25 degrees or so) then I would start suspecting water flow issues. Or, even air flow across radiator.

Thanks David

Fan was spinning before and after I tightened the fan belt. I can turn the fan by hand and didn't notice anything weird when I installed the new belt. I'll pull it back off and check to see if the bearings are locking up.

I like the idea to check the inlet and outlet temps. Wish I had done that before to have data to check against.

Like DavidF says- after running the engine, is the lower radiator hose cooler than the top one?

And I would check the coolant level again to see if you notice any changes.


*lag time, I see you read that

Yeah, the coolant level is definitely going to be lower after yesterday, there was antifreeze coming out around the cap. Now that I think about it could that be the problem? Could the cap be bad and not holding any pressure causing it to overheat?

Are you referring to a 2nd series 1955 235 truck engine in a 1952 3100 truck?

What psi radiator cap are you using?

" . . it has the older water pump on it and the fan sits low . . " The older 216/235/261 water pump sits higher than the newer 235/261 water pump.

What is the code pressed into the block in the ledge to the rear of the distributor?

Tim, yes a 55 235 in a 52 3100.

7 psi cap

Is the code you're talking about the serial number? I have 0012298T55Z wrote done as that.

Block casting is: 3837004
Head casting is: 3836848

Or, it's holding too much pressure- like the coolant is in a pressure cooker... or, there's too much coolant in the engine... or, the radiator is clogged.

I'm going to let someone else chime in here with a better answer for you, but in my case (similar to yours) I had a 59 year old original radiator that was too clogged up. When I tried to back flush it from the bottom end with an air nozzle wrapped up in a towel, it sprang an entire congregation of new leaks (that the clogs had been holding), so I ended up replacing it.

The thermostat (somebody correct me) in the pump controls the water flow, so be sure to check its function, as well.

I wonder if it dislodged some crud when it overheated so now the radiator is partially plugged?

Dennis

I may have it fixed. I topped off the radiator and ran it up to temp and it didn't appear to be going above normal. So I went for a little trip up to the Fire Station and borrowed a laser thermometer and checked everything. It agreed with the temp gauge where it goes into the head. The top of the rad was about 180-185 and bottom was running 155-165, hard to get a good reading down there with it running.

I did notice that there appear to be some coolant leaking out around the rad cap so I first thought I should replace it. So while I was looking up the part number of the last one I bought in my receipts I found out its a 4 PSI. Should I be able to run a 7 PSI cap? This is still the original Harrison radiator from a 52 3100.

The 1952 radiator cap was 4 psi.

The 160 degree thermostat in 1952 was fully open at 180 degree.

Thanks Tim I'm sure I knew that but didn't even think about looking there.

And just checked and nobody has one in town. Had to order one and wait till 10:30 in the morning to change out the cap.

So I don't know what you mean "leaking out around the cap" but a 4 lb cap will allow coolant to come out when the pressure exceeds 4 lbs. You also need some space in the top of the tank for expansion.

Take the thermostat out and put it in boiling water and see if it opens. 9 outta 10 times it's the t stat. Might want to check your plugs also if you were over heating, the clean one will be a head gasket leak which is another can of worms. Also note that 212 isn't too crazy as long as there is coolant in the radiator. Modern cars operate at 200 normal temp, all day long.

I would check the t-stat like Hollow65 suggests, then replace it with a new one which has the little air bleed hole in it to purge the air that gets trapped in the head. I have had t-stats hang up in the closed position intermittently, making diagnosis very challenging. T-stats are cheap, so I replace them when I have overheating problems.

I'm going to pick up a new thermostat when I get the radiator cap today. I'm also going to flush the old coolant while I'm in there and replace with fresh antifreeze and distilled water.

I'll check the new thermostat before installing and test the old one once it's out. If it's still good I'll have a spare 160.

Forgot to mention I'm going to check the plugs and hope they're all dirty. Don't hear that to often.

I would definitely stay with the 4psi cap when using old original radiators. Those radiators were not designed to hold a lot of pressure to begin with. Add age and you are asking for trouble.

Definitely check and/or replace the thermostat.

Temperature variance across radiator was in the proper range.

Another cause of temperature issues is a leaking head gasket. If you get combustion gases in the coolant, it causes little bubbles in the coolant which in turn cause the water pump to cavitate and not flow coolant properly. Open the radiator cap, run the engine and look for small bubbles.

early stovebolts/GUAGES,just good stuff.guys already got this one covered it sounds to me like.good luck on your bolt

UPDATE
Sat I checked the new thermostat before I installed it and it didn't open until 180, so it's going back.

I drained the coolant and refilled with tap water then drained it again. I pulled the old thermostat and set it aside and reconnect the thermostat housing and connect a piece of pvc pipe to the top radiator hose instead of radiator. I plugged the radiator inlet with a rag and started water running from a garden hose thru the radiator and out the top hose. Once this was clear and clean water I tried a test. I had the radiator overflowing with water and stated the truck, the water pump would pull down the level in the radiator faster than my garden hose could fill it so I'm sure it's not the pump. I left the thermostat out and reconnected the top radiator hose and added a bottle of Prestone Radiator Flush and Cleaner Additive. Then I drove around for about 25-30 minutes. It struggled to reach 180 until I parked it.

While it was cooling down so I could drain it again I tested the old thermostat and it started opening at 160 and was fully open at 180. I drained the flush and cleaner out, re-installed the old thermostat and filled with distilled water and anti-freeze. I then ran the truck with out the radiator cap until the thermostat opened, watching the coolant level the whole time.

I did notice a few tiny bubbles in the coolant so it may be the head gasket. I had checked all of the plugs earlier and they all were all normal, not clean. So I'm thinking there may be a small leak from the exhaust into the coolant and with that and the fan belt being loose after I changed it that may have lead to the overheating.

On my drive in this morning the gauge never got about 180 which is normal. I'll see what it does this afternoon on the way home when it's in the 90's. I am going to get my hands on a Engine Block leak test kit and test for CO in the coolant. Then I'll know if I need to change the head gasket for sure.

Thanks everyone for their suggestions.

It's been over a month and I finally got around to renting the block test kit from a FLAPS. The fluid stayed blue and didn't turn yellow which would show the presence of exhaust gasses in the coolant. I've not had any issues with overheating since then either so I'm going to call it good.