Does a water pump work or not?

[slocrow]

I spoke earlier with a member who offered his thoughts so thanks, it helped plenty.
I finally started chasing down an  overheating when standing and idling ongoing problem today. It's now much better with the few changes made but I want more. Prior to today's changes my temp would just continue to climb while sitting and idling; 190, 200, 210 and around 220 I went nuts and took evasive action. That would usually occur after a run to a show and then getting caught in the gate traffic and that would happen in 5 to 10 minutes. Down the highway it would run between 180 and 190 depending on stuff but no real problem.
With a local show to attend tomorrow, I decided to attack the problem today, typical. I pulled and changed the thermostat from a 160 to a 180 and replaced the cap with a 16#er. I fired it up and let it idle in my garage with the doors open and when it got to 160 I flipped on the electric fan. To my surprise it idled for a half hour and pretty much stayed around 190/195 though near the ½ end it did manage to creep up to 202ish but a BIG improvement.
With my temp gun I noticed that my gauge was pretty much right on with the reading I was getting at the intake by the thermostat housing where the sensor is installed. In other words if my gauge said 190 the gun said 192, at the sensor but as I traveled up the rubber top hose the temp would drop as follows; 1/3 up=182; 2/3 up=174 and on the top tank to the left of the hose I got a reading of 167/165ish on the aluminum Griffin. Where did the heat go or am I not circulating efficiently, hence my question? Exit temps were 157 at the radiator bib and 144 almost at the pump (stainless pipe with hose ends) though the iron pump showed much hotter.
The block is a 396 +30, oval ports, lumpy cam and headers with an RPM intake and 750 Edelbrock.
Now my question; can the water pump lose efficiency causing the temperature variation up the upper hose or does a pump either work or not?
Thanks for looking and any thoughts.
Happy 4th, Frank

[enjenjo]

What do you have for a water pump? Rebuild, new stocker, or aftermarket?

Do you have vacuum advance, and does it advance at idle? On my Buick, if I hit two stop lights close together, it would overheat, I replaced a defective vacuum advance, and that cured it.

[slocrow]

What do you have for a water pump? Rebuild, new stocker, or aftermarket?

Do you have vacuum advance, and does it advance at idle? On my Buick, if I hit two stop lights close together, it would overheat, I replaced a defective vacuum advance, and that cured it.

Hi Frank, thanks again. It's a rebuilt stocker and maybe that's a flow problem? I wanted to see what the result of these changes were before other moves. I took it foe a run and idel parked when I got home and it got to 210 but slower then before o'plenty.
I'm running a mechanical advance and vacuum is planned but I have to pull the engine some to change, or cut the firewall, not. I'm a 12' and was thinking of moving it up to 14' and see if that makes a difference but one step at a time. Timing next!
What about pump efficiency, any thoughts for that temp variation?

[Warpspeed]

As I traveled up the rubber top hose the temp would drop as follows; 1/3 up=182; 2/3 up=174 and on the top tank to the left of the hose I got a reading of 167/165ish on the aluminum Griffin.

It sure does sound like there is insufficient water flow at idle.
Could be very high leakage around the pump impeller, or pump not turning fast enough.

I would pull the pump and have a look inside.
Check out some pictures of a few replacement pumps on the internet, and see if you can spot one with a bigger more meaty impeller that fits your engine.
Some engine variants come with different engine pulley sizes and pump impeller sizes and fan sizes for different vehicle applications.
You may have fluked an unfortunate combination, high rpm pump, and slow pump  pulley size.

The way this works, a manufacturer may decide to turn the fan faster to get a lot more air, and then fit a smaller capacity pump to reduce high rpm cavitation.

It may also be worth  flushing out the radiator just to be absolutely sure there is nothing in there restricting the flow.  
Its very rare, but I have heard of people finding a rubber "flapper" lurking inside one of the radiator hoses where the rubber has de laminated and folded back on itself.

[slocrow]

As I traveled up the rubber top hose the temp would drop as follows; 1/3 up=182; 2/3 up=174 and on the top tank to the left of the hose I got a reading of 167/165ish on the aluminum Griffin.

Some engine variants come with different engine pulley sizes and pump impeller sizes and fan sizes for different vehicle applications.
You may have fluked an unfortunate combination, high rpm pump, and slow pump  pulley size.

The way this works, a manufacturer may decide to turn the fan faster to get a lot more air, and then fit a smaller capacity pump to reduce high rpm cavitation.

Well now, there's food for thought. Thanks...

[wayne petty]

well... some theory...

water pump impellers...  there are several issues...

some impellers on universal type of water pumps have straight fins so they will function in normal or reverse rotation..

there are also normal rotation water pump and reverse rotation water pumps... these have blades that pull in from the center and push outward..

normal rotation pumps have blades like this \\\\\\\\\\\\ so the coolant is pushed toward the outside...

reverse/left handed operation water pumps have blades ////////// again.. so the coolant being pushed outward is forced..

when the universal straight finned blades are used.. |||||||||  those just kinda  well i don't think i should describe what they do or don't do here..

there is one last issue that i have not run across yet in chevy water pumps but have run across in some asian water pumps..  plastic impeller blades that crack and spin freely on the shaft .. so instead of pushing water around with some force.. they just barely move it around.


do you have a bypass circuit??? where coolant flow trapped behind the closed thermostat can get back to the water pump to be sent around picking up heat from the cylinders and cylinder heads where it will flow past the thermostat again and again until it picks up enough heat to open the stat ...  more below..

since you have an infrared temp gun...

can you see the engine temps coming up steadily.. circulating thru the bypass hose until the thermostat opens and hot coolant flows into the radiator..

so now we have hot coolant that opened the thermostat and caused the pump exchange the cooler coolant into the engine where it should have closed the thermostat..   allowing the now stationary coolant in the radiator to be cooled by either ram air or from air pulled thru by the fans..

the coolant should exchange and exchange again and again.. with the engine stabilized within 15 degrees or so of the thermostat opening temp..

a 180F thermostat will usually operate at 190F  
a 192F thermostat will operate at 195 to 220F.. depending on if its cooled by belt driven fans or electric fans that cycle on and off..

say... thermostatic fan clutches are designed to operate with a 192 F thermostat..  they generally don't turn on until the air flow thru the radiator is above 190..  so if you have a 160 or a 180 stat it.. the coolant will have exchanged several times before the thermostatic fan clutch turns on..  an overheat will soon result..


lets see...

with a thermostat installed and the bypass circuit that is smaller than the flow the water pump can create causes increased mechanical coolant pressure .. this is a GOOD THING.. each pound of pressure increase raises the boiling point of the coolant 3F.  this stops the coolant from boiling around the hottest spots in the engine.. around the exhaust ports and exhaust valve seats..  hint.. the bypass circuit keeps the coolant circulating past these hot spots to keep them from boiling the coolant causing steam bubbles..


lets talk pressure...

i have had a bunch of radiator caps with loose, dangling discs in the center of the rubber seal..  these are designed to be pushed closed by expanding coolant..  i toss these out.. find a similar version with a disc thats spring loaded..

with marginal sized radiators... and 160 or 180 temp thermostats..
you can reach a point where the thermostat has circulated several times without loosing enough heat causing the thermostat open wider and wider.. this is a runaway cooling system and is kinda what you described above.  as the coolant is flowing so fast thru the radiator that no amount of fan forced air or ram air thru it will cool it...

there is also the issue that water pumps at moderate engine speeds and above move water like a fire truck. massive amounts..  the pressure in the upper tank can be so high that it expands the tank and causes it to deform and leak.. either blowing out the seals or cracking the solder joints..  there is an issue on circle track cars with aluminum radiators and 30 pound radiator caps.. that the extreme high pressure and flows expand the oval tubing and closes off the air flow thru the radiator..  dirt in the radiator can have the same effect... wash them out with a garden hose.  thru the fins..

so cars and trucks that have an overheating issue..

unless it was one of the few that were designed with a 180F thermostat..

swap in a 192F thermostat.. the last digit of the part number will be a 9 in most brands... XXXX9 for a 192F..

the 192F thermostat will keep the system operating above ambient air temps to increase the ability to cool the system.

i know there is more...

like the amount of air moved by belt driven fans.. or CFM of electric fans...

even voltage drop because of undersized wiring to the electric fans.. or like earlier in the week..  where the electric fans were on all the time and drawing down the battery voltage making it very hard for the charging system to keep up...  reduced voltage draws more amps.. decreases electric fan speed... a dangerous downward spiral into thermodynamic runaway...

[enjenjo]

I am not a big fan of part store rebuilds, I have had too many problems. I have used Stewart water pumps to cure problem systems several times in the past

You might try another experiment. Advance the static timing about 10 degrees at idle, and see if it makes it cool down. If it does, a vacuum advance hooked to manifold vacuum may be your answer.

[Rochie]

This is the best explanation of the need for vacuum advance I have come across

This was written by a former GM engineer as a response to a similar question on a Camaro board:


As many of you are aware, timing and vacuum advance is one of my favorite subjects, as I was involved in the development of some of those systems in my GM days and I understand it. Many people don't, as there has been very little written about it anywhere that makes sense, and as a result, a lot of folks are under the misunderstanding that vacuum advance somehow compromises performance. Nothing could be further from the truth. I finally sat down the other day and wrote up a primer on the subject, with the objective of helping more folks to understand vacuum advance and how it works together with initial timing and centrifugal advance to optimize all-around operation and performance. I have this as a Word document if anyone wants it sent to them - I've cut-and-pasted it here; it's long, but hopefully it's also informative.

TIMING AND VACUUM ADVANCE 101

The most important concept to understand is that lean mixtures, such as at idle and steady highway cruise, take longer to burn than rich mixtures; idle in particular, as idle mixture is affected by exhaust gas dilution. This requires that lean mixtures have "the fire lit" earlier in the compression cycle (spark timing advanced), allowing more burn time so that peak cylinder pressure is reached just after TDC for peak efficiency and reduced exhaust gas temperature (wasted combustion energy). Rich mixtures, on the other hand, burn faster than lean mixtures, so they need to have "the fire lit" later in the compression cycle (spark timing retarded slightly) so maximum cylinder pressure is still achieved at the same point after TDC as with the lean mixture, for maximum efficiency.

The centrifugal advance system in a distributor advances spark timing purely as a function of engine rpm (irrespective of engine load or operating conditions), with the amount of advance and the rate at which it comes in determined by the weights and springs on top of the autocam mechanism. The amount of advance added by the distributor, combined with initial static timing, is "total timing" (i.e., the 34-36 degrees at high rpm that most SBC's like). Vacuum advance has absolutely nothing to do with total timing or performance, as when the throttle is opened, manifold vacuum drops essentially to zero, and the vacuum advance drops out entirely; it has no part in the "total timing" equation.

At idle, the engine needs additional spark advance in order to fire that lean, diluted mixture earlier in order to develop maximum cylinder pressure at the proper point, so the vacuum advance can (connected to manifold vacuum, not "ported" vacuum - more on that aberration later) is activated by the high manifold vacuum, and adds about 15 degrees of spark advance, on top of the initial static timing setting (i.e., if your static timing is at 10 degrees, at idle it's actually around 25 degrees with the vacuum advance connected). The same thing occurs at steady-state highway cruise; the mixture is lean, takes longer to burn, the load on the engine is low, the manifold vacuum is high, so the vacuum advance is again deployed, and if you had a timing light set up so you could see the balancer as you were going down the highway, you'd see about 50 degrees advance (10 degrees initial, 20-25 degrees from the centrifugal advance, and 15 degrees from the vacuum advance) at steady-state cruise (it only takes about 40 horsepower to cruise at 50mph).

When you accelerate, the mixture is instantly enriched (by the accelerator pump, power valve, etc.), burns faster, doesn't need the additional spark advance, and when the throttle plates open, manifold vacuum drops, and the vacuum advance can returns to zero, retarding the spark timing back to what is provided by the initial static timing plus the centrifugal advance provided by the distributor at that engine rpm; the vacuum advance doesn't come back into play until you back off the gas and manifold vacuum increases again as you return to steady-state cruise, when the mixture again becomes lean.

The key difference is that centrifugal advance (in the distributor autocam via weights and springs) is purely rpm-sensitive; nothing changes it except changes in rpm. Vacuum advance, on the other hand, responds to engine load and rapidly-changing operating conditions, providing the correct degree of spark advance at any point in time based on engine load, to deal with both lean and rich mixture conditions. By today's terms, this was a relatively crude mechanical system, but it did a good job of optimizing engine efficiency, throttle response, fuel economy, and idle cooling, with absolutely ZERO effect on wide-open throttle performance, as vacuum advance is inoperative under wide-open throttle conditions. In modern cars with computerized engine controllers, all those sensors and the controller change both mixture and spark timing 50 to 100 times per second, and we don't even HAVE a distributor any more - it's all electronic.

Now, to the widely-misunderstood manifold-vs.-ported vacuum aberration. After 30-40 years of controlling vacuum advance with full manifold vacuum, along came emissions requirements, years before catalytic converter technology had been developed, and all manner of crude band-aid systems were developed to try and reduce hydrocarbons and oxides of nitrogen in the exhaust stream. One of these band-aids was "ported spark", which moved the vacuum pickup orifice in the carburetor venturi from below the throttle plate (where it was exposed to full manifold vacuum at idle) to above the throttle plate, where it saw no manifold vacuum at all at idle. This meant the vacuum advance was inoperative at idle (retarding spark timing from its optimum value), and these applications also had VERY low initial static timing (usually 4 degrees or less, and some actually were set at 2 degrees AFTER TDC). This was done in order to increase exhaust gas temperature (due to "lighting the fire late") to improve the effectiveness of the "afterburning" of hydrocarbons by the air injected into the exhaust manifolds by the A.I.R. system; as a result, these engines ran like crap, and an enormous amount of wasted heat energy was transferred through the exhaust port walls into the coolant, causing them to run hot at idle - cylinder pressure fell off, engine temperatures went up, combustion efficiency went down the drain, and fuel economy went down with it.

If you look at the centrifugal advance calibrations for these "ported spark, late-timed" engines, you'll see that instead of having 20 degrees of advance, they had up to 34 degrees of advance in the distributor, in order to get back to the 34-36 degrees "total timing" at high rpm wide-open throttle to get some of the performance back. The vacuum advance still worked at steady-state highway cruise (lean mixture = low emissions), but it was inoperative at idle, which caused all manner of problems - "ported vacuum" was strictly an early, pre-converter crude emissions strategy, and nothing more.

What about the Harry high-school non-vacuum advance polished billet "whizbang" distributors you see in the Summit and Jeg's catalogs? They're JUNK on a street-driven car, but some people keep buying them because they're "race car" parts, so they must be "good for my car" - they're NOT. "Race cars" run at wide-open throttle, rich mixture, full load, and high rpm all the time, so they don't need a system (vacuum advance) to deal with the full range of driving conditions encountered in street operation. Anyone driving a street-driven car without manifold-connected vacuum advance is sacrificing idle cooling, throttle response, engine efficiency, and fuel economy, probably because they don't understand what vacuum advance is, how it works, and what it's for - there are lots of long-time experienced "mechanics" who don't understand the principles and operation of vacuum advance either, so they're not alone.

Vacuum advance calibrations are different between stock engines and modified engines, especially if you have a lot of cam and have relatively low manifold vacuum at idle. Most stock vacuum advance cans aren't fully-deployed until they see about 15" Hg. Manifold vacuum, so those cans don't work very well on a modified engine; with less than 15" Hg. at a rough idle, the stock can will "dither" in and out in response to the rapidly-changing manifold vacuum, constantly varying the amount of vacuum advance, which creates an unstable idle. Modified engines with more cam that generate less than 15" Hg. of vacuum at idle need a vacuum advance can that's fully-deployed at least 1", preferably 2" of vacuum less than idle vacuum level so idle advance is solid and stable; the Echlin #VC-1810 advance can (about $10 at NAPA) provides the same amount of advance as the stock can (15 degrees), but is fully-deployed at only 8" of vacuum, so there is no variation in idle timing even with a stout cam.

For peak engine performance, driveability, idle cooling and efficiency in a street-driven car, you need vacuum advance, connected to full manifold vacuum. Absolutely. Positively. Don't ask Summit or Jeg's about it – they don't understand it, they're on commission, and they want to sell "race car" parts.
Written by JohnZ,
Washington, Michigan

[slocrow]

Thanks guys, as I'm off to the show and will report back later.
Yes wayne, big block by-pass to pump.
Good idea Frank as to how to check at idle; value of vacuum.
Later, Frank

[Harry]

I found two Chinese water pumps for my LT1 with NO impellers.

[phat rat]

I found two Chinese water pumps for my LT1 with NO impellers.

Now that's a good example of Excellent quality control

[Arnold]

I found two Chinese water pumps for my LT1 with NO impellers.

Now that's a good example of Excellent quality control

 I changed a bad pump.The "rebuilt one" was a very good quality name.
It was going in a van so what if it is 3 times the cost of a cheap one
  NOT when it started circulating..oh no I won't..maybe I will..a bit.
 
  I pulled the pump apart..they had pressed a new cheap impeller on a shaft that was pitted..and starting to flake off..the impeller slipped..and was starting to chew things up..then it would grab a bit as the hole in the impeller got a bit more chewed up.

[Arnold]

As I traveled up the rubber top hose the temp would drop as follows; 1/3 up=182; 2/3 up=174 and on the top tank to the left of the hose I got a reading of 167/165ish on the aluminum Griffin.

It sure does sound like there is insufficient water flow at idle.
Could be very high leakage around the pump impeller, or pump not turning fast enough.

I would pull the pump and have a look inside.
Check out some pictures of a few replacement pumps on the internet, and see if you can spot one with a bigger more meaty impeller that fits your engine.
Some engine variants come with different engine pulley sizes and pump impeller sizes and fan sizes for different vehicle applications.
You may have fluked an unfortunate combination, high rpm pump, and slow pump  pulley size.

The way this works, a manufacturer may decide to turn the fan faster to get a lot more air, and then fit a smaller capacity pump to reduce high rpm cavitation.

It may also be worth  flushing out the radiator just to be absolutely sure there is nothing in there restricting the flow.  
Its very rare, but I have heard of people finding a rubber "flapper" lurking inside one of the radiator hoses where the rubber has de laminated and folded back on itself.

 I had a new piece of neoprene fuel line do that :evil: .Couldn't tell from the outside. Only allowed a trckle through.
 I think I did throw some parts at it before I figued that one out

[Warpspeed]

Yeah, its pretty rare, but once you have seen it, you never never forget....

[wayne petty]

for those who want to mess around...

i happen to know a water pump parts supplier out here in los angeles..  i buy bags of replacement press in tubes from them for various projects..

but they have bearings and seals and impellers....

ASE Industries Inc
1920 Griffith Ave, Los Angeles