1968 Engine running hot and overheating

[Moon's74]

OK, so you did have the hood on for the last test, I must have missed that. The fan shouldn't have done much for you at highway speeds so I guess the water pump and removal of the t-stat was key. Good enough for me to get a new, better, water pump.

Looking forward to hearing how putting a t-stat back in effected it. No hurries, just enjoy it for now. Thanks.

 

[DaveLev]

I know that in 2 months I'll need to do this. I need to remove the radiator anyway to extend the upper hose bung thing anyway (my proposed fix to the unbelievable short hose issue - different thread). When I do that, I will try putting the stock 5 blade fan back in and see what happens with that high volume water pump. Will report back in a week or so on this issue - may do it on Saturday, but radiator shop open Monday and probably will need to keep it overnight :-(

 

[pcf_mark]

Do you have a photo of the back of the pump you took off? I think that pump was reverse rotation.

 

[DaveLev]

It may have been but not certain it was. I hooked my drill to it and put it in the sink and it definitely sucked in from the large lower hole and pumped out the top two holes, but that's as scientific as I got. Never removed back plate. Was a solid re-manufactured water pump with no identifying marks on it at all. I returned it for full refund. With all I spent with this particular aftermarket parts supply house, there was no way there were going to refuse or argue with me.

 

[Mtgrizzlymn]

I'm going to bend over and buy a 7 blade fan I guess


Sent from my iPad using Tapatalk

 

[blubuckaroo]

It may have been but not certain it was. I hooked my drill to it and put it in the sink and it definitely sucked in from the large lower hole and pumped out the top two holes, but that's as scientific as I got. Never removed back plate. Was a solid re-manufactured water pump with no identifying marks on it at all. I returned it for full refund. With all I spent with this particular aftermarket parts supply house, there was no way there were going to refuse or argue with me.

You would have to pull the cover to know. Even if you reverse the rotation of a centrifugal pump, the liquid will still flow in the same direction. Just not nearly as efficiently as it needs to.

 

[DaveLev]

Mtgrizzlymn: Sorry lack the free time to pull everything and piece it back together to find out what was the main fix, but I suspect the thermostat removal and waterpump had the biggest impact, and removing the shroud and radiator to get to the fan, well, the water pump was right there, and the garage floor was ruined anyway so I pulled the thermostat. Replacing everything at once was not as scientific as others may have wanted, but honestly I have about 22K into a bronco I could probably not sell for 12K right now, and just wanted it running and driveable as soon as possible for my wife.

BluBuckaroo, thank you for saying that even if reverse rotation the liquid flows the same direction. That piece I did not know. I assumed the veins inside either pushed one way or the other, and if you reverse rotated it probably wouldn't have flowed as high as the other, but honestly without a flowmeter of sorts - hydrometer? - I would not have been able to measure the volume. My water pump appeared to flow just fine based on the non-scientific test I did in my utility sink, but I did not compare clockwise to counter clockwise - I only mimicked the direction of the correct rotation, and it appeared to flow fine.

Honestly, if I were to do it again, I would have started with pulling the thermostat out of the housing first, then the upgrade of the fan, then the water pump last. Instead, the order I went was radiator, timing, carburetor jetting/tuning, plugs/cap/rotor, thermostat, system pressure test, water pump, thermostat again, hydrocarbon test, fuel filter/sender, head gaskets, valve job/top end rebuild, hydrocarbon test again, timing again, and as a last resort the water pump/thermostat removal/fan upgrade.

I'm upset just typing this, frankly, and have no idea if I put a thermostat back in if I will see the same problems again. In essence, I have kicked the proverbial can down the road until it gets cold in late October when I will put a thermostat in and report back results.

 

[blubuckaroo]

Mtgrizzlymn: Sorry lack the free time to pull everything and piece it back together to find out what was the main fix, but I suspect the thermostat removal and waterpump had the biggest impact, and removing the shroud and radiator to get to the fan, well, the water pump was right there, and the garage floor was ruined anyway so I pulled the thermostat. Replacing everything at once was not as scientific as others may have wanted, but honestly I have about 22K into a bronco I could probably not sell for 12K right now, and just wanted it running and driveable as soon as possible for my wife.

BluBuckaroo, thank you for saying that even if reverse rotation the liquid flows the same direction. That piece I did not know. I assumed the veins inside either pushed one way or the other, and if you reverse rotated it probably wouldn't have flowed as high as the other, but honestly without a flowmeter of sorts - hydrometer? - I would not have been able to measure the volume. My water pump appeared to flow just fine based on the non-scientific test I did in my utility sink, but I did not compare clockwise to counter clockwise - I only mimicked the direction of the correct rotation, and it appeared to flow fine.

Honestly, if I were to do it again, I would have started with pulling the thermostat out of the housing first, then the upgrade of the fan, then the water pump last. Instead, the order I went was radiator, timing, carburetor jetting/tuning, plugs/cap/rotor, thermostat, system pressure test, water pump, thermostat again, hydrocarbon test, fuel filter/sender, head gaskets, valve job/top end rebuild, hydrocarbon test again, timing again, and as a last resort the water pump/thermostat removal/fan upgrade.

I'm upset just typing this, frankly, and have no idea if I put a thermostat back in if I will see the same problems again. In essence, I have kicked the proverbial can down the road until it gets cold in late October when I will put a thermostat in and report back results.

I actually enjoy this stuff. Especially when there is a positive end to the story.
I've seen very few cooling issues caused by a water pump. HP water pumps and spinning them faster is a waste of time and $$$.
Overheating is caused by a real problem that should be fixed before throwing $$$ at the problem.
Good factory equipment is all you should need unless you're racing. But then you'll be looking for sponsers to pay for the stuff.

 

[DaveLev]

I have removed the 7 blade FoMoCo fan and put on the stock 17" FoMoCo fan. I made some modifications to the radiator as well. Check out this thread at: http://classicbroncos.com/forums/showthread.php?t=268903 where I will be posting images within a few hours.

 

[DaveLev]

Alright...having backtracked a bit in my overheating journey, here's today's findings.

For the sake of research and in the spirit of 'giving back' to the community, I swapped my fan from the huge 7 blade to the 5 blade fan, and took a road trip.

It still has no thermostat in the housing, and still has the new edlebrock water pump, and the hood is still on, and the same pulleys, and the same 1" spacer, it still has the stock shroud on...basically an identical test as I did about 2 weeks ago.

In the driveway at idle for 30 minutes with the radiator cap off to bleed the system so to speak revving the throttle every few minutes to burp anything out, the temperature remained around 170.

I put the cap on and within a few minutes it had climbed to about 180.

I took it on the side streets for a bit in 3rd gear topping out around 50 MPH. Temperature hit 190 to 200 in that test.

I then hit the freeway at 65 in 4th, and it started around 195 degrees, but quickly climbed to 210 degrees.

I took it even faster - closer to 80 MPH - for a brief time, and it climbed to 220 degrees.

This experiment replicates the same behavior I had originally when I thought it was possibly the head gaskets or thermostat or water pump (and subsequently replaced everything and did the head job, too).

In conclusion, the fan - whether in town or on the highway - appears to play the largest role in keeping the bronco cool *for me*. The results I saw were staggering. As you may recall I could drive it two weeks ago at or above 80 MPH for up to 30 minutes in hotter temperatures and the rig would still maintain about 205 degrees tops, whereas today while it is about 20 degrees cooler outside the rig hit 220+ within 10 minutes of freeway driving.

Thoughts anyone?

My next non-scientific test will be to swap back to the larger 7 blade fan (which also has fins that protrude at least 1" further than the stock 5 blade), and when I swap the fan I will put a bigger spacer on it to bring it closer to the radiator and I will also NOT put in the fan shroud to see what that does.

I hope to hear back from the few of you still following along soon!

Thanks for reading.

 

[DaveLev]

I had an epiphany last night, and rather than do a test without the shroud, decided to try the following:

Remove stock 5 blade fan again;
Remove aftermarket 1" fan spacer;
Install factory 1/4" spacer;
Install 7 blade fan;
Install shroud.

My thinking was that it only rubbed the shroud with the bigger fan, so by reverting back to the stock spacer and larger fan I should be okay.

I was not.

The 7 blade fan still rubbed the shroud.

The 7 blade did not, however, hit the upper radiator hose. Why? Remember I extended the upper radiator bung by almost 2", so the fan now sits about 1/2" away from the hose.

To fix the rubbing fan, I cut away about 3/4" of factory shroud half way around the shroud (at the bottom, and up each side about 1/2 way.

During road test, fan not rubbing.

So, how was the temperature difference?

Remember it still has the aftermarket high volume water pump and no thermostat in the housing, etc. Only change was to fan and shroud.

During idle in driveway, never went over 170 (just as with the 5 blade fan).

Jumped on the freeway, and climbed very slowly to 190 degrees at 65 mph (about 15 degrees less than yesterday, and it's hotter today than yesterday - go figure). So even at highway speeds, the 7 blade keeps it cooler.

In order to see if I could make it overheat, I drove 85 MPH for about 20 minutes (legal here). It stayed around 210 degrees, about the same as it did with the 5 blade fan, but 20 MPH faster with the 7 blade fan at same temperature.

To push it to the max, I went 90+ MPH for 7 minutes, and temperature climbed to about 218 but never exceeded 220. So I was able to drive about 10-15 MPH faster with the 7 blade fan before hitting 220 degrees. My guess is that at this speed you are at the point of diminishing returns, and for every MPH faster I go the temperature will climb faster than it does closer to 60 MPH.

After going 90+, I got off the freeway and filled up the tank, and the temperature gauge stayed at 220. When I started back up no problems, and drove onto the freeway at 65 MPH and the temp went back down to 190, as it was before I was doing the 80+ MPH tests.

I burned $20 in fuel trying to get it to overheat and to report back this data.

Next step: Install factory overflow if I can find one. Right now overflow just going to the ground.

 

[DirtDonk]

That last should keep you from having to check and fill the radiator all the time at least.

I think you're getting there pretty quick now. But you're never really going to have a way (I don't think) of keeping the temperatures completely down at those higher speeds Dave. These rigs are just not at their best at that point.
You've got aerodynamic issues in all aspects at those speeds.
Air blocking effect of high pressure and turbulent points under and over the vehicle.
More and more power being used, and heat being generated, by the engine to push the box through the air. Requiring even more of the capacity of the cooling system than would normally be expected of it.

Those two aspects I suspect are key here. You're dialing in the details that make for an efficient system with each test and change you make. But at some point the phone booth going 90 mph down the road is just not going to allow full efficiency from any system.

I'm sure you could make other changes that compensate for that, but they may be more than you feel like making at that point.

Paul

 

[tortoiseracer]

So I think you have still not answered the question. From what I hear your fan now fits better in the shroud so it may not be the fan but the better fitting shroud to fan. Next show us a picture of how the shroud fits the radiator. If it was just the fan/shroud fitment it would have probably had a lower temp after your gas start. It says you have too much blockage in front of the radiator. (I think you said you had an air conditioner condenser) or your shroud does not fit your radiator properly not pulling enough air through the radiator at lower speeds. I also agree at higher speeds you are going to see higher temps. Flat nose vehicles with flat windshields just push too much air and engines working harder make more heat.

 

[DaveLev]

I'm not sure what the question was. What I do know is that the stock five blade smaller fan was in the correct position with the correct spacer in the stock factory shroud and it ran a lot hotter than it did with the seven blade larger fan. I did this same test about two weeks ago when the fan was occasionally hitting the shroud and the temperature and speed I was doing mimics the test I did today. Previously, the 7 blade fan was on a 1 inch spacer. It rubbed the fan shroud then. It also came close to hitting the upper radiator hose. Since I change the radiator by extending the bung, I could remove the one in spacer and go back to the factory spacer which is a quarter-inch. You could say I never solved the original problem in that the gap between the upper radiator hose and my radiator was 5 inches, but to get between my lower radiator hose and the radiator was just two or 3 inches. I never found an upper radiator hose that would reach that did not hit my fan.

In summary, the stock fan fit in the shroud appropriately. The seven blade fan I purchased which is over 19 inches wide and has blades that sit about 2 inches further back than the stock fan barely fit in the factory shroud regardless of fan spacer.