water pump/overheating head scratcher

[redstone65]

A couple of weekends ago I replaced the timing cover gasket on my 240. It had a bad leak. While I was in there I figured go ahead and replace water pump and thermostat just for insurance. The water pump still spun fine, but was badly rusted internally.

The FoMoCo I removed looked like this:



The new one from NAPA looks like this:



I'm no water pump expert, but how can this function properly without holes in the impeller for block-side suction?

I've started overheating since doing this change. My first thought was bad thermostat, so I removed it. Truck still gets up to about 175 with no thermostat, which seems high. So, I bypassed the heater core with a straight loop of hose and still gets up to about 175. Heater core is only a few months old and flushes clear, but just being thorough. I'm now wondering if this water pump is garbage since the only thing in the loop now is water pump and radiator. The pump doesn't leak, but maybe it's just not pushing enough coolant with that funky design. Radiator has some corrosion inside but when I flush it I get plenty of flow and it has no detectable leaks.

Any ideas or thoughts?

[oldsmiley]

If you weren't heating before, but you ARE now, I'm like you. All arrows kinda point to the pump. If you didn't throw you old one away yet, you should be able to take a puller and swap the blades to make sure.

I'd say it's THAT, or your sending unit went haywire at the same time and isn't reading correctly. Kinda odd but NOT impossible........

Where was you reading at before.

[redstone65]

Where was you reading at before.

I was running a 195F thermostat since December and it pretty much always stayed right there. I took multiple interstate trips at 60mph and never had any issues. On the way back from work today in the heat (85F in Birmingham) it topped out about 180F at 50mph.

I first started noticing the issue this past Friday when making a longer trip (70 miles) up the interstate. I look down and I'm running a little over 200F at 60mph (ambient temp was 96F), so I backed it off to 50mph and it dropped back down to 185F. Radiator cap definitely popped because I had coolant residue on the valve cover and air cleaner when I got home.

I'll look at swapping the impeller this weekend. Not sure I have the right puller, but I have a few so I'll see. I guess I should also get a new radiator cap. Not sure how old this one is. Looks ok, but you never know.

Should have just bought the Motorcraft pump. It was only $20 more.

[Toyz]

Uhh, "block side suction"? That would be "recirculation"! I don't think that would be a good thing!
Beware switching impellers; replacements don't always hold OEM tolerances., and it would be fun getting the clearances right without damaging the mechanical seal.
Also note that Ford is very specific about coolant level, it should barely be visible in the top tank.
Since a heater core is simply a heat exchanger, any circulation there would have the effect of lowering operating temperature.
You mentioned "a couple weekends ago", that seems to match the timeline of your distributor replacement IIRC.
Have you checked the amount of total advance your new one has, and at what rpm, as compared to the original?
Also, a proper thermostat, does more than allow quick engine warming. It also acts as a flow control device; the lack of one may allow too much flow to effectively cool, especially noticeable at highway speeds.
I am unable to find any factory reference to a 195 degree thermostat for an early 240; no problem, that is not your current problem.
So, before you attempt to remove an old sheet metal impeller, then align it on the new shaft to proper clearances without damaging said mechanical seal (damage which may not manifest itself immediately), my suggestion would be to check and compare total timing settings.
I suspect your efforts will be better spent swapping springs than rebuilding a new water pump.

[redstone65]

Uhh, "block side suction"? That would be "recirculation"! I don't think that would be a good thing!

Ok, based on your comment, I think I've misunderstood the coolant flow.

Does this highly detailed, beautifully drawn diagram seem accurate?

Have you checked the amount of total advance your new one has, and at what rpm, as compared to the original?

The water pump came about a week after the distributor swap I think. The same day as getting the new water pump, 180F thermostat and timing cover gasket all swapped out, I did play with the timing a bit. I re-found TDC more accurately because I never trusted my marks on the HB. Then I reset it to about 9 degrees at idle, which seems happy. I was trying to fix the dieseling issue I've been having, thinking that the timing may be too advanced. I also put some octane booster in the gas to see if that helped the dieseling.

[Toyz]

Yep, an impeller takes up liquid from the center and expels it circumstantially. An "open" impeller design, or semi-open" dispels liquid against a backing wall of some sort. I suspect NAPA's suppliers' design is a matter of parts interchangeability as much as any other design focus.
So, I am not quick to condemn the new pump. As noted, I would stick a thermostat back in to bring back the "metered" flow rate to give the coolant a chance to do it's job at higher RPM. As you likely surmised, after 40 years of repairing and teaching HEI, I am far from a fan of the current crop of off-shore clones. I have seen too many worrisome issues with them.
They are NOT made specific for our applications, so they often are nowhere near the factory timing curve, and since obviously built for a price , quality control is largely left to the consumer.
You can see where this is heading; by all means, check the centrifugal advance; if it advances, check it against the factory curve for the 240. It is not unusual to find the advance stuck or non-functional, let alone far off OEM specs.
You mentioned "dieseling", if this just started with the new distributor, there's your clue! Also, vacuum sourced from manifold will give you additional advance at idle, thus adding to the tendency to "diesel" and lack suitable advance when accelerating, which can tend to "heat things up". If you currently are running manifold (below throttle plate) vacuum, switch back to ported per the original setup, and your issues may disappear barring any additional issues.

[redstone65]

Thanks for all the help Paul. The dieseling was happening even with the old distributor. That's why I went to the higher octane, since I wasn't convinced it was a timing issue. It hasn't done it a single time since I re-set the timing and put the octane booster in, so one of those two things are the culprit. I'm going to switch back to straight 87 octane on the next tank without changing the timing and see what happens.

That's a good point about the advance curve. I will check that also when I put everything back like it should be tomorrow. I'm not using manifold vacuum. I'm using the carb port vacuum.

BTW, I don't see any timing difference with the vacuum attached or not while idling. It behaves the same either way. I guess it could be a screwed up advance canister or just maladjusted. If so, could that mean that the timing at interstate speed is too retarded and leading to overheating? I think that would fit with your theory.

[Toyz]

With ported vacuum, you will see little to no additional at idle.
The main thing as to timing is the operation of the centrifugal advance. It needs to loosely duplicate the factory curve, and return to base timing at idle.
I'm basing my thoughts on the <10% noted temperature increase, which is often symtomatic of insufficient advance at highway cruise.
It may well be working properly; but the symptoms and timeline make it well worth checking. A 180 degree thermostat might allow some relief from the dieseling; if it was consistently running above that setting, it may not.
It should not be dieseling with added octane; killing the engine while in gear will usually prevent dieseling, but still leaves the posibility of un-noticed detonation at higher RPM. That scenario, however, is not consistent with the thought of insufficient higher RPM advance, while it COULD be consistent with elevated operating temperatures.
Gotta start somewhere!

[Lowell]

is your idle speed faster than now than it was ? A fast idle will cause deiseling when you shut it down.

[redstone65]

Ok, this is the internet, so I could theoretically just lie or abandon this thread.

I will do neither!

I'm going to fess up to the fact that I had put the thermostat in backwards. Once I reinstalled it oriented the correct way, I drove all day yesterday and it was rock solid at 180.

My original misunderstanding of the direction of the coolant flow, which Paul corrected, had led me to put it in backwards. That, and the fact that it goes in much easier facing backwards than forwards because of the little ridge on the t-stat housing. Putting it in with the spring/element facing block side makes it want to fall out. It just seemed correct the other way. [sigh] That was originally why it overheated. And then, when I took the t-stat out (and bypassed heater core) as a troubleshooting step, that was the wrong thing to do as well since it removed the regulating factor as was mentioned earlier in the thread.

The odd thing is, back during winter, I had swapped out the 180 that was in it with a 195 for a little better heat in the cab. I had also put that one in backwards, with the bull nose of the t-stat facing the engine block and the spring facing the radiator. It's my daily driver, and I drove it for months that way and never got over 195. I have no idea how that's possible. My only theory is that the heater core was doing most of the cooling, and since it was winter, everything was ok. My drive to work is only 10 minutes, so maybe it just never got hot enough to be problematic. IDK.

So, basically, this was me chasing my tail (and yall's) for a week. Sorry about that guys.

[slick4x4]

Good to know

I doubt anybody around here will rib you about making a mistake

There's only 2 types of mechanics that have never made a mistake

#1 those that have only been a mechanic a VERY short time
#2 liar

[Toyz]

Glad you got it! Your experiences can prove helpful to our members!
That's how we all learn.
As to the old one working, I suspect your winter thermostat was not the "fail-safe" design made to "fail open". The other logical possibility is that the winter heat load was maneageable even with the backward thermostat, since it would still open from the heat.
I've learned to listen to Pat, he speaks with wisdom for a youngster!

[slick4x4]

[redstone65]

Thanks guys. On the bright side, I now have the cleanest 1965 240 engine block water passages in North America. That’s what flushing the cooling system 10 times will do.