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Reverse rotation water pump? water pump off, question??

simpleman83

simpleman83

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Ok, i've done some searching but I can't figure out how to tell if my PO put on the wrong type of water pump or not... I know since I have the 88 with TBI with serpentine that it should be reverse rotation...correct? Also, I was able to look at the pump and come up with A-06 and PH-388 what do these mean? If this doesn't mean anything, is there anyway to tell the reverse rotation from the forward without taking it off?

*EDIT* The lower hose is hot and the upper hose is room temp or whatever, so that just the one side of the radiator is hot and the other side cool where the top hose comes in. Which direction should flow be going? and shouldn't both hoses be the same temp?

Can someone clarify on the serpentine setup? I seem to have a combination of two v-type belts and a flat, serpentine like belt and I'm wondering if the PO mixed and matched somehow crazy.Is this normal for the 87-90?

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Does it overheat? I think that would be my criteria as to whether its right or not.

Regardless, that isn't a reverse rotation water pump setup AFAIK, reverse would be all serpentine and the water pump belt would be UNDER the pulley. Not that the wrong water pump couldn't be on there, just unlikely if it doesn't overheat.

Yours looks like the setup that came out of the '87 Monte SS I grabbed mine from. Looks like it's missing pieces too. (power steering pump bracket for one.)
 
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it is overheating, thats what I'm trying to fix, I've already replaced the radiator and the tstat.... I'm mostly wondering if there is anyway to tell if it is reverse rotation definately without taking it out completely.
 
I guess what we really need to know then, which you asked, is if there are external differences to the pump we can check. Obviously pulleys could be changed, so even if the belt setup is wrong on yours, it doesn't mean the pump is right.

Did you search the boards for posts about reverse rotation pumps? I *think* there was at least one where someone had the wrong water pump, perhaps the symptoms will give you a clue, if they posted them.

As a matter of fact, if all I had to go on was visual evidence, I'd say that's the wrong water pump. Those spacers on the power steering/water pump bolt, coupled with the lack of serpentine and other brackets, leads me to believe someone swapped on a non-serpentine setup but didn't realize the pump was different. If/when you replace it, make sure to get a pump that matches up with your power steering bracket. I believe you can get one that has a threaded hole in that location, so no spacers and a nice short bolt.
 
The spacers are taking up space that used to be occupied by the A/C mount, according to the PO.
We removed the tstat and the engine would not even get warm, and the top hose was much warmer than the bottom hose after having it run for a while.

So, we know that the coolant is flowing from the engine through the top hose to the radiator and then through the bottom hose to the engine. (top hose is significantly warmer) Is this the correct flow direction? This should tell us whether the waterpump is correct or not.
 
I hope someone steps in here to make sure I'm not incorrect in saying this, but...

my understanding is that this is not a reverse cooling setup. Coolant never flowed in a different direction (IE it still comes from the lower hose and out the upper) only that the impeller was changed to allow it to still pull coolant when the pulley rotates the opposite direction due to belt routing.

That said, if the engine isn't warming up with no thermostat, it's probably not the wrong pump. Incorrect pump should result in little to no cooling with or without a thermostat, since the water isn't moving.

It shouldn't heat up at all with the thermostat out, it's a fallacy that no t-stat equals overheating as you've just proven.

It would seem to me that the thermostat was faulty. How hot did you let it get? Typically the thermostats are "sticky" and let it get over 195* a bit, before the coolant temp drops off quickly.
 
dyeager535, it's just reverse rotation on the water pump, not reverse cooling - that's only the LT-1. Get it good and warm and turn the heater on full-shot. Pull the radiator cap - if it's not flowing, you probably have the wrong pump. Your return from the heater core will give you a good idea as to the amount of flow. All systems I've ever worked on flow out the bottom of the radiator, then back in the top. Logic says it would be impossible to cool if it had to pull from the top and your radiator was even a couple of inches low on water. Out the radiator, into the block, into the heads (either parallel or series flow), then back into the radiator. This also makes sure that the water is warmed by the block before it hits the heads which helps keep the heads from cracking if you add cold water.
 
Has it overheated since you bought the truck? or is it just a recent thing? The pump looks like it has been there a little while, at least long enough to rust. Your truck requires a regular (clockwise) rotation water pump.
Are you sure the engine isn't just air locked? try removing the coolant sensor to purge the air.
The top hose should be getting warm as the engine warms up, the lower hose is the inlet and should be cooler if the radiator is working properly.
An easy (although not 100%) way to tell if it is: Most regular rotation pumps use standard threads for the pulley and the reverse rotation pumps use metric. I have seen a few pumps get built with the wrong impeller, so who knows. Fortunately water pumps aren't that difficult or expensive to replace.
 
GM trucks did not go fell serpentine until 1989. The belt configuration you have is stock for every truck from around 1985-1988. The water pump that "should" be on that truck would be normal rotation. With that being said a new water pump isn't much money so why not just install a new pump. Just remember, order a standard rotation pump. Also did you install the thermostat the correct way? The spring end goes into the intake manifold. The flow of water is from the radiator through the lower hose and into the engine then out of the upper hose and back into the radiator.
 
hard to say

so, I know for certain that all 3 thermostats that I have tried are good and release between the 190-200* mark by the boiling test.... so I'm positive its not the tstat. and I just replaced the radiator so thats good as well, brand new. So, by running the NO TSTAT test, the engine does not over heat and ends up being fine no matter whether I run the fan, shroud, etc. its fine, so in my Opinion, its gotta be the water pump.... Any other opinions acceted into concideration becasue I'm lost. The higher hose, closer to the tstat IS running hotter than the lower hose. which means its pumping out of the heads, and not hitting the heads first. From all the posts, I understand that it should be forward rotation so, is this the correct direction, drunk now, morning later....
 
Have you brought into question your gauge?

I don't see where my reasoning is flawed thinking that if you can keep the engine cold with no thermostat, the pump can NOT be bad.
 
dyeager535, I agree totally. Part of the reason for the thermostat is to make the engine run at optimum temperature, generally 180* - 200*, depending on the setup. With thermostat out, it'll take longer to warm up but otherwise it should be fine.

If it's been run a few times and it's still getting hot, it's doubtful that it needs to be "burped", it should have taken care of that when the the t-stat was pulled and ran it without one.

Simpleman83, are you sure you're getting the thermostat in facing the right direction? The heat sensor belongs on the bottom where the hot water is coming from. If it's in upside down, it'll do exactly what you're describing. If it runs cool with no thermostat, it can't be the water pump. Flip the thermostat and give it a shot.
 
Yeah, that's what i was going to say.. make sure the thermostat is in the right way.. that's what it sounds like to me. But if you have different pullys on your engine and a different belt set up then normal.. you might have to switch to the reverse direction pump... If the belt set up you have on there came from a vehicle with a reverse pump, you'll need to run a reverse pump. Only difference is which side of the pump pully the belt runs on. .. .. .. .. .. And all radiators flow top to bottom.
 
Well, I put the tstat back in and got the thing running, just let it idle till it started getting hot. The gauge still says that its getting hot, but at idle it will rest around 3/4 of the way hot... no clue what temp, about to use some thing that my buddy has to measure the temp internally. I'm seeing that the top hose still isn't getting warm, whereas when I had the tstat out, it would, I know for a fact that tstat I put in is working correctly because we boiled it and it worked. Now, the tstat should be installed with the bigger, copper, sensor thing (where 195* is engraved on it) down correct?? I really hope that that is because I would feel like a huge tool if not. Going to test temp, any other suggestions appreciated..
 
From what 4X4 is saying, that's a normal setup. I assumed (wrongly) that the setups were serpentine earlier on, so it sounds like he probably has the right stuff on the truck.

His pulley setup is normal rotation, and the pump probably is too, no reason to *think* the wrong one would have been installed. I'm just reiterating this because I don't want the OP to chase his tail here based on what I thought originally.

With the setup all put together, radiator down a quart or so of fluid (so you can see flow) are you getting good movement of coolant when the engine is warm?
 
it looks like yes the fluid is flowing through the radiator. my buddy can't find the temp tester so I think the test is going to be to drive around and see if its still overheating or if it was just not burped correctly or whatever, if it overheats then we still have a problem. After the first time it overheated, I didn't let it overheat again, just watched the gauge climb. Maybe it is just the gauge....
 
So we just ran it for about 30 minutes and just drove around the parking lot and not too hard or anything. It never physically overheated, as in, radiator boiling over or whatever, the gauge read HOT, and the upper hose never got warm, the bottom hose was super hot and the top one was almost cold. So, does this mean that the tstat is somehow restricting? even though I tested it and it was good, and installed with spring side down, as discussed earlier???? or do I even have a problem still, the only reason I'm thinking I do is that the upper hose isn't hot after being run.
 
I'd take it to a trusted mechanic as soon as possible. Let him know everything you've tried so he doesn't have to spend his time (and your money) trying the same things you are trying. You can end up chasing your tail and replacing a bunch of parts that don't need it and costing a lot more than paying him to do it right. I know this is frustrating as hell for you but it makes more sense to spend a few bucks getting it diagnosed correctly than taking a chance of cooking your block.
 
If you drove it for 30 minutes and it didn't boil over, you've at least got SOME coolant transfer...I think it would have boiled over if the t-stat was stuck shut. Besides, you are seeing coolant move. The bottom hose isn't collapsing is it?

Upper hose should definitely be hot, and be pressurized when you squeeze it. What happens when it's hot and you try (VERY carefully) to remove the radiator cap? What happens if you leave the cap off and let the truck warm up? (watch the radiator and the temp gauge)

There isn't much to this system. Your radiator can't be the problem, or it would overheat with no thermostat, plus it's new. Your thermostat could be faulty, although you've tested it. If it stays shut, the upper hose may not get hot, but it should warm up at least.

Thermostat STILL sounds like the problem, although your water pump MIGHT be bad, perhaps the impeller is shot. What happens if you drive around with the t-stat out? If you repeat your 30 minute drive with no t-stat and it doesn't overheat, it has to be it. The water pump is obviously moving enough coolant in that case. If coolant isn't being moved even with no t-stat, the engine will overheat. Should overheat in park as well.

I've never looked at a reverse rotation pump, but this is my only other idea. If the pump IS reverse rotation, it could possibly pull coolant the wrong way? Did you happen to notice when you pulled the t-stat, if coolant was still coming from the drivers side through the radiator, dumping into the passenger side radiator tank??
 
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