: Can a Water Pump Be Bad Without Leaking Or Making Noise?



chevyorange
04-27-05, 02:02 PM
OK, I've seriously narrowed down my overheating trouble to when I'm travelling at freeway speeds and going up grades of 10% or more.

Changed: thermostat, flushed and filled coolant, Water Pump Tensioner.

Can a Water Pump not circulate enough coolant (in other words, be bad) without leaking, making noises or otherwise obvious outward appearances?

I promise this will be my last cooling system question! I'm nearly fully competent on Northstar!

Thanks, guys.

Adam

mcowden
04-27-05, 03:58 PM
This might be a long shot, but have you felt the hoses? I've heard of hoses that were collapsing under high flow conditions before. There's something in there to prevent collapse, but maybe it's broken? It's unlikely, but all I can think of right now. I can't picture how a water pump could lose flow at high speed other than a plugged vapor vent line perhaps or a collapsing hose. I'm definitely not the foremost expert here (or anywhere for that matter), and in fact, according to g2mtu I'm just a pimply-faced kid. Either way, it's easy to feel the lower hose.

Ranger
04-27-05, 04:00 PM
Not likely but then anything is possible. Have you checked the purge line from the pump to the surge tank to be sure it is not plugged. If so, and there is any air in the system the pump can cavitate.

chevyorange
04-27-05, 04:04 PM
OK. I bought a new water pump but am not going to swap it out yet. The hoses look good but how to know if they are collapsing?

Here is what is happening now, I'm getting it more and more nailed down.

The car can start and idle/drive from cold to warm up just fine. It will continue to run fine up to about 75MPH level with no adverse effects. As soon as there are high speed bursts or going up grades anything other than level, the temp starts creeping up.

Today, when it overheated, I pulled over, and as soon as I could I checked the overlow tank - it had plenty of coolant in it! It only started pouring out when I popped the cap it started going through the overflow tube.

I added about 1/4 bottle of 50/50 mix, put the cap on, started the car, and drove home without incident.

I'm very frusturated! I thought maybe I had a head problem but this time all my coolant was there - if it were a head gasket wouldn't it "burn" the fluid to cause it to overheat?

The old LT1 was pretty cut and dry when having cooling system problems.

Again, idler checked out, new belt, new thermostat (not even sure the old one needed replace), filled 50/50 mix coolant and two tubes of Bars Leak. Hoses aren't leaking, aren't brand new but aren't cracked or wasted from the outside. 91K original miles on a 1994.

I'll pay cash money for someone to come over here and fix this thing! You doin't know me, I don't know you, under the table! My three torn disks just can't take anymore!

Adam

chevyorange
04-27-05, 04:06 PM
Not likely but then anything is possible. Have you checked the purge line from the pump to the surge tank to be sure it is not plugged. If so, and there is any air in the system the pump can cavitate.

When I changed the thermostat, I used pressurized air back through the purge line to the overflow and it was making the trip just fine, not even a hint of a hiccup. I wish it were that!

Another thing, when I got home after my last trip, the car ran fine the rest of the trip, actually running cooler than normal. When I stopped the car, I could hear burbling in the overflow but nothing was being spit out, only lasted about 20 seconds and then silence.

malcolm
04-27-05, 04:19 PM
I saw on a recent "Weekend Mechanic" show on cable a test for clogged radiator. The top and bottom hoses were removed and the top taped shut with duct tape. Holding a hand over the lower hose outlet the radiator is filled with water. When full, remove your hand and the water should gush out in seconds. Anything less than a total douche would indicate a clogged radiator. I have persoanlly had clogged heater core problems. That would suck since most are burried pretty well.

BeelzeBob
04-27-05, 04:55 PM
If the Northstar water pump pulley is turning the water pump impeller is turning and pumping. There is virtually no way that the pump can not pump if the pulley is turning as you imply/ask.

I would say that the answer to your question is NO...there is no way that the pump can be bad and not pump. Even if it is leaking or noisy it will pump. The only way it will not pump is if the pulley is not turning due to the belt, tensioner failing or the water pump bearing seizing up completely...but that should be pretty obvious as the water pump drive belt would smoke....

zonie77
04-27-05, 08:47 PM
Chevy, I hate to tell you this but I am 99.9% sure it's head gasket failure.

At the beginning they show up under load, so hills or high speed. As they fail further the overheating gets more consistent. My brother's acted this way. It drove us nuts because we didn't want to believe it was head gaskets. As we loosened the head bolts we were sure, but even then the gaskets did not look bad. It took some careful inspection to find the leaks. A compression test was not real definitive. While 2 cyls were low they weren't real low.

Too bad we are so far apart!

eldorado1
04-27-05, 11:38 PM
Chevy, I hate to tell you this but I am 99.9% sure it's head gasket failure.


That's what I thought when he first said it only did it under load... I wanted to let him exhaust all other options first :(

BeelzeBob
04-28-05, 01:57 PM
The way to quickly tell for sure is to pull the plugs, put shop air at 120 PSI into each spark plug port and watch the cooling system for bubbling.....this will positively check the head gasket integrity.

chevyorange
04-28-05, 01:59 PM
Thanks bbob, I'm off to do that.

I have been pretty sure this was the problem too, but I wanted to explore all cheap options first.

Anyone recommend a good shop/tech in the greater Seattle area? I'd do anything to stay away from the dealership. Will pay cash (of course!).

Thanks for all your help!

Adam

BeelzeBob
04-28-05, 02:46 PM
I just made an adapter to do that check and it is very easy. Find an old spark plug, take it to a bench grinder and grind off the rounded, rolled ring on the top of the spark plug shell. Takes 90 seconds. The porcelean will slide right out with your fingers or light tapping this way. Run a 1/8 pipe tap into the ID of the shell from the outside/hex side of the shell. Screw a 6 inch, 1/8 pipe nipple into the shell and put an air quick connect on the other end and you are done. The ID of the plug shell is almost perfectly the size for tapping with a 1/8 pipe tap so you don't even need to drill it. Make sure the piston for that cylinder is at TDC so the engine won't spin, pressurize it with shop air and watch the surge tank for bubbling. I just drop a piece of wooden dowel down the spark plug hole, turn the engine with the accessory drive belt to bring it to TDC per the height of the dowel and screw in the adapter.

chevyorange
04-28-05, 03:06 PM
Brilliant! Thanks for a great tip - I'm not all that creative and this is excellent! Hopefully others stop in this thread and pick up the idea!

Aam

MtlSphere
04-30-05, 11:02 AM
When I changed the thermostat, I used pressurized air back through the purge line to the overflow and it was making the trip just fine, not even a hint of a hiccup. I wish it were that!...

Sounds like you may have only done half the job there...did you also check the hollow bolt that that line attaches to?

That's where my obstruction was. So clogged in fact I had to use a dremel with a drill bit attachment to clean it! It hasn't overheated since. :burn:

chevyorange
04-30-05, 12:00 PM
Ah, a "hollow bolt". How did I miss that?

I'll go give it a look, thanks.

Spyder
04-30-05, 08:46 PM
Back when I was having overheating problems...which by the way ended up being my own stupid failure to check if the electric fans were running...they were not...but anyways, I tried and tried to find the hollow bolt and the line everyone talks about, but didn't ever notice it...I'm probably just blind, but good luck! :)