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How To Tell If Coolant Is Circulating - Auto


Zero Knievel

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Want to pick some brains here.

 

I'm doing some much needed maintenance on my pickup.  It was over a gallon short of coolant (eek), and the heater barely puts out warmth.

 

I'm running cleaner in the system and will flush it Saturday...just to clean out any gunk.  I'm pretty certain the thermostat has failed, and I will dismount the radiator to have it pressure checked for leaks.  I'm not losing any significant amount of fluid from the system since I've been driving it.

 

As it's not getting "hot", the upper return hose never gets that firmness you feel when the thermostat opens and lets hot coolant flow.  However, there is no way to visually determine if coolant is circulating (which it should if the thermostat is stuck open).

 

I suppose I could detach the upper hose and risk coolant (water) spraying everywhere when the engine starts up, but the only other way I know to check the condition of the water pump is to dismount it and try to get a peek into it to see if the impeller blades look damaged.  It's not a "hard" job, but it's a good bit of work just to remove it.  Of course, it's an 18-year-old truck with over 200K on it, so maybe I could just replace the pump for the Hell of it.

 

Thoughts?

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Don't overlook a compromised head gasket, especially if you're seeing diminishing coolant volume but don't see any evidence of a leak. If the coolant passage holes in a head gasket are compromised traces of coolant can find its way into a combustion chamber and be vaporized--you'll very likely never see typical evidence of a cooling system leak (puddles, etc.). A blown head gasket will also have a effect (sometimes almost too slight to detect, but not always) on the overall pressure in the system when running. I agree that your thermostat may be suspect (stuck open). A  "soft" hose that won't firm up might just be old, but may also point to a system pressure issue.

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11 minutes ago, ironmike said:

Don't overlook a compromised head gasket, especially if you're seeing diminishing coolant volume but don't see any evidence of a leak.

 

That's something I hope I don't find.  Normally, burning coolant shows up in exhaust smoke, but if it's minor, I suppose one would not see anything.  I would also see evidence if the oil looks cloudy, but I've not done the oil yet.

 

I'm really hoping to find something common, like a pinhole leak in the radiator.  This truck saw almost no use since last winter.  It sat in a gravel drive most of that time, and for it to be so low with no sue, I don't think a blown head gasket would make that happen.  A slow leak onto gravel...definitely possible to miss that.  The parking area only recently (3-4 months) was paved, so it's likely the fluid loss happened before then.

 

Oddly enough, no issues with overheating...even when the fluid level was so low.  I could say part of that was the weather (40-50 degrees), but I'd think you'd still have a boil over situation brewing with that much coolant missing from the system.

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Mike,

does the truck have any temp gauge on the dash?

does it move off of cold to the place you are used to seeing?

If so, then you at least have coolant in the block.

 

Heater cores get blocked.  Most coolant systems will circulate water through the heater core before the thermostat opens fully. 

So if your gauge is moving, and you are getting some heat, I would assume some coolant flow.

 

Check your oil. Engine, and transmission if equipped with a cooler.  Water from a leak will give a milky white residue.

If the oils / fluids look normal, I would worry less about a head gasket.

Another symptom of head gasket failure is bubbling/ overflowing of the radiator with the engine running, cap removed.  I have seen this described as looking like a volcano.

 

Also, remember that coolant will slowly flow out of the radiator fill, cap removed, as the engine warms up.

This is normal.

In proper operation, just like your bike thread, the coolant should warm in the block first.

Then the thermostat opens and coolant flows through the radiator. 

The whole system warms, and builds pressure as the coolant expands during heating.

At some point, the pressure of the system will exceed the pressure rating of the pressure cap.

The cap then allows the expanded coolant to vent to the overflow bottle.  This venting stops when enough coolant has moved to lower the pressure.

When the engine is off and cools, the system pressure will drop, and coolant in the overflow will be pulled back into the radiator.

 

This all happens, assuming good seals on the radiator cap, a good sealed overflow hose,. And a overflow tank that isn't leaking.

If there are leaks, you will only pump coolant overboard, and not pull it into the system for the next use.

Not recovering the coolant will leave air in the radiator. This causes the system to heat faster, overflow some more and recover less the next time.  

 

I would first check that your gauge is working.  Top off the radiator and take it for a drive. If the gauge doesn't show overheat, then let it cool and check your coolant level in the radiator again. It should be close to where it was when you filled it.

If lower, then clean the seals on the cap and radiator, and inspect the overflow tank and hose.

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9 minutes ago, redxxrdr said:

does the truck have any temp gauge on the dash?

YES

 

does it move off of cold to the place you are used to seeing?

Stays at the bottom BUT I do need to test if the gauge is working (simple) as my sensor for the gauge might have gone bad.  If the gauge works, the manual says to replace the sensor.  Even in this condition, SOME heat should register (some movement in the needle).

 

Heater cores get blocked.  Most coolant systems will circulate water through the heater core before the thermostat opens fully. 

So if your gauge is moving, and you are getting some heat, I would assume some coolant flow.

I get lukewarm to warm from the heater, but at the same time, I can run the truck for a half hour and remove the cap with little to no pressure behind it.  So, my guess is that the coolant just isn't getting hot enough.  Too bad I didn't decide to get on this when we had temps in the 90s.

 

Another symptom of head gasket failure is bubbling/ overflowing of the radiator with the engine running, cap removed.  I have seen this described as looking like a volcano.

I've not seen this (cap off and engine running), so here's hoping.  There has been a "foaming" issue, but that was when the system was short by over a gallon of fluid, and it could have been anything foaming the coolant (like cavitation in the pump).  I still see some now, but the system is filled with water + super flush, and that stuff tends to foam a bit.  In both cases, it's right as I remove the pressure cap.

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Finish flushing the system, have the radiator pressure-checked (if it makes you feel better), replace the thermostat, re-fill with water & anti-freeze, THEN see if all those other symptoms go away.

FYI, if the coolant was being "burned" through the engine, the likely problem would be the intake manifold gasket, not the head gasket.

If this is a Chevy, go with DBLXX's suggestion. :-)

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Not knowing any thing about the history of this truck, like a previous owner attempting to remedy the same problem by running a flush threw it and not getting all the flush out of the system,( or neutralizing it properly) this can cause thermostat failure, and over time eat the impellers off the pump.with this in mind rest and other contaminants can and will stop up the heater core. Were it my truck, I would replace the water pump with a new one, I have seen rebuilds that the impellers have come loose on the shaft not allowing proper circulation of coolant . replacing the thermostat is a no brainer. fill the system with water only, if the temp comes up and there is still little or no heat from the heater, next place is the heater (temp)  control valves, are they operating properly, ? Last and certainly not least, the heater core is stopped up. they are not expensive to buy, and there are many sources for them. but the bitch is changing one out. 

Good luck, will be interested in what you find.

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Dismount the radiator for a test; you just love doing things the hard way don't you....for fuck's fuckin sake why don't you just drive the truck to the shop?!?

 

Easy thermostat check: with the radiator full, cap off, engine cool, start it and look.  There should be no flowing water, if the thermostat is open there should be noticeable flow/movement of the water.  If the thermostat is working the heater hoses should start to warm up shortly after start up, water flows through the core regardless the thermostat position.  If the therm. is bad the heater hoses will still warm up, but it'll take longer and they'll never get very hot since the water isn't getting hot.  Since you're opening the system up I'd pull the heater hoses off and back flush the core with a garden hose, stuff tends to collect in them and back flushing should clear it up.  If I knew what you were working on I could probably point the way to which hose is in/out, I'm much more capable with vehicles than mind reading.

 

The thermostat doesn't need to open for there to be pressure in the system, it'll start pressurizing as the engine warms up, you probably just have a cap issue or a really big leak.  Most Fords will have pressure just from the morning sun warming things.  Not sure that it's only a Ford thing but I see it more often with Fords.....but I also have several of them at any given time.

 

A smart guy looking for help would at least state the make of the truck, if not year, model, eng. size.

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5 hours ago, DBLXX said:

 

We are praying you find it and junk the piece of shit and save us the next 94 posts on "how do I" about this shit box in 2017 :) 

Sign me up for the prayer group....

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So I believe that narrows it down to a 2.3, 3.0, or 4.0.  The most common is the 2.3; gutless, but economical & reliable and very easy to work on.  The 3.0, to me, is a worthless "upgrade" that just consumes more gas for little more power.  The 4.0 in that little truck is pretty peppy while being not much more thirsty or hard to work on than the 3.0.  So let's think a moment..........I'll guess he has the 3.0.

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Before taking anything apart pressure test the system. It leaking or its not. Running for a half hour should be plenty even in the cold. Sender to the gauge has always been a common failure I have seen. Gauges rarely fail. Fords have shunt gauges which are idiot lights with a spiffy needle that often is not calibrated. 

  Warm the engine and check its temp with a infrared temp gun. 

A gallon low on coolant means you were cooking the motor.

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Just went through this with a friend of mine this past weekend.  He knew for a fact he had a crack in the radiator, as he could see it leaking out of the bottom.  But he was also seeing intermittent coolant on the floorboard.  Obviously, that screams heater core, but when I opened the box, it was dry.  We put a radiator in it and already had the heater core, and when I cut the hoses off (23 years old, they aren't coming off any other way) the corrosion on the inlet side of the heater core was so bad that it had made a pinhole in the hard line and was leaking coolant out that was dripping on the ground while running.  The intermittent on the floorboard was actually the coolant finding the path of least resistance from time to time and running along the pipe and going through the firewall. 

We get all that done, refill the radiator, he cranks it up, no flow through the radiator.  Truck starts overheating within 90 seconds.  Shut it down, bought a thermostat and a water pump to eliminate all options.  Turns out it was the thermostat locked in the closed position, but the impeller had rust on it and probably would have let go in the next year anyway.  Refilled it and as soon as he started it, it sucked down the coolant level.  You can tell if it's flowing because if everything is as normal, the water should be rushing through the radiator with the cap off, which you can visually see.

Also, check to make sure you don't have a crack in your reservoir.  The coolant could be leaking there if you don't have leaks anywhere else.  By the way, a new radiator is usually only $100 or so, and having a radiator repaired is nearly that much.  Might as well get a new one and not worry about it.  Also significantly reduces downtime.

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13 hours ago, srideaux said:

Not knowing any thing about the history of this truck, like a previous owner attempting to remedy the same problem by running a flush threw it and not getting all the flush out of the system,( or neutralizing it properly) this can cause thermostat failure, and over time eat the impellers off the pump.with this in mind rest and other contaminants can and will stop up the heater core. Were it my truck, I would replace the water pump with a new one, I have seen rebuilds that the impellers have come loose on the shaft not allowing proper circulation of coolant . replacing the thermostat is a no brainer. fill the system with water only, if the temp comes up and there is still little or no heat from the heater, next place is the heater (temp)  control valves, are they operating properly, ? Last and certainly not least, the heater core is stopped up. they are not expensive to buy, and there are many sources for them. but the bitch is changing one out. 

Good luck, will be interested in what you find.

 

1998 Mazda B3000.  Sorry, I figured I'd mentioned that enough times in the past that people just knew.

 

Until I got the Prius, I used it all the time and took meticulous care of it.  It's pretty much sat in the drive unused and neglected for the last 3 years.  My bad.  When I changed coolant, it was always deep cleaned and backflushed before refilling.  Radiator was replaced once already.  Heater always got hot enough to dry herbs in the cab (except when the thermostat failed).  So, the thermostat has been replaced at least once.  How I lost so much coolant is a mystery.  I opened the cap last night and there was no air in the system and no foaming from the day's drive to and from work.

 

On Saturday, I will backflush the system.  I'll see what comes out.  I'll change the thermostat.  IF I test it, I'll just fill it with water and see if it heats up.  If so, I might just stop there and do a drain/refill with 50/50 mix.  I'm still inclined to take the radiator in for testing and see if I can see the impellers through the hose connection to the coolant pump.  There is no dripping from the coolant system overnight.  I'd expect to see something if I had a leak.

 

13 hours ago, superhawk996 said:

Dismount the radiator for a test; you just love doing things the hard way don't you....for fuck's fuckin sake why don't you just drive the truck to the shop?!?

...

The thermostat doesn't need to open for there to be pressure in the system, it'll start pressurizing as the engine warms up, you probably just have a cap issue or a really big leak.  Most Fords will have pressure just from the morning sun warming things.  Not sure that it's only a Ford thing but I see it more often with Fords.....but I also have several of them at any given time.

 

It's a LOT cheaper to take the radiator into the shop than have a mechanic test it on vehicle.  More so, while the B3000 has a plastic/metal radiator, so repairs aren't always possible, a minor leak in the metal section can be repaired for a fraction of the cost of replacement.  Also, the shop specializes on radiator testing and repair, it's not a general auto shop (which would only tell you to replace the radiator).  When my first XX radiator sprung a leak, this shop patched it up.

 

9 hours ago, XXBirdSlapper said:

Before taking anything apart pressure test the system. It leaking or its not. ... Sender to the gauge has always been a common failure I have seen. ...

A gallon low on coolant means you were cooking the motor.

 

So far, no leaks.  I'm expecting to have to replace the sender unit.  Fortunately, I was running AMSOIL, so I had some extra protection against heat damage.  I'm not sure of all the codes, but the only engine code in the system is that the coolant isn't getting warm.  No codes for excessive motor heat.  Motor runs fine as if nothing's wrong.  It's also fortunate that it was pretty cold when I used the truck and found the shortage in coolant...that might have helped.  Honestly, without the thermostat, I wonder how much heat the motor retains (OEM opens at around 190).

 

7 hours ago, Furbird said:

Also, check to make sure you don't have a crack in your reservoir.

 

That I know is fine.  If I was losing coolant there, it would be obvious.  I made the mistake of assuming that coolant in reservoir = coolant in radiator.  Since it was filled, I figured I was fine when I wasn't.

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17 hours ago, DBLXX said:

We are praying you find it and junk the piece of shit and save us the next 94 posts on "how do I" about this shit box in 2017 :) 

 

Are you crazy?  It's paid for!  Fixing a minor issue like this is chicken scratch compared to buying even a "new" used pickup.  More so, as I hardly use the pickup any more, I certainly can't justify replacing it just so the replacement sits most of the time in the garage.

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12 hours ago, XXBirdSlapper said:

Before taking anything apart pressure test the system. It leaking or its not. Running for a half hour should be plenty even in the cold. Sender to the gauge has always been a common failure I have seen. Gauges rarely fail. Fords have shunt gauges which are idiot lights with a spiffy needle that often is not calibrated. 

  Warm the engine and check its temp with a infrared temp gun. 

A gallon low on coolant means you were cooking the motor.

The oil pressure gauge on many of them is an idiot light with a needle, the "sender" being just an on/off switch.  While the temp gauges may not be 'calibrated' I've never had one that didn't show a logical indication of temp.  A gallon low is scary, but not necessarily damaging; I've seen worse.

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2 hours ago, Aunt Zero said:

 

1998 Mazda B3000.

 

It's a LOT cheaper to take the radiator into the shop than have a mechanic test it on vehicle.  More so, while the B3000 has a plastic/metal radiator, so repairs aren't always possible, a minor leak in the metal section can be repaired for a fraction of the cost of replacement.  Also, the shop specializes on radiator testing and repair, it's not a general auto shop (which would only tell you to replace the radiator).  When my first XX radiator sprung a leak, this shop patched it up.

 

So far, no leaks.  I'm expecting to have to replace the sender unit.  Fortunately, I was running AMSOIL, so I had some extra protection against heat damage.  I'm not sure of all the codes, but the only engine code in the system is that the coolant isn't getting warm.  No codes for excessive motor heat.  Motor runs fine as if nothing's wrong.  It's also fortunate that it was pretty cold when I used the truck and found the shortage in coolant...that might have helped.  Honestly, without the thermostat, I wonder how much heat the motor retains (OEM opens at around 190).

 

That I know is fine.  If I was losing coolant there, it would be obvious.  I made the mistake of assuming that coolant in reservoir = coolant in radiator.  Since it was filled, I figured I was fine when I wasn't.

Somehow I guessed it was a 3.0, almost scary.

 

I don't see how it's cheaper to test it off the car since there's more work involved, it also won't test the system.  So if you find there's no radiator leaks you still need to find the leak which means a system pressure test.  If that shop can test a loose radiator they can test it in the car and it's less work, stop guessing and just call them if you don't think so.  Most parts stores have loaner testers, get one and do it yourself.  Test it cold, if nothing then do a hot test, but cold will generally find more leaks than hot.  "the shop specializes in radiators and fixed your XX radiator"....you mean the one that was still leaking and had to be replaced???  Yea.

While a plastic/aluminum radiator can leak in the metal part, I've only found one that did and it had an obvious manufacturing fuck up.  I've only replaced about 50 radiators tho so I'm sure yours will be the exception.  If it has sprung a leak in the metal section I would not have it repaired, I'd replace it.  If it's old enough that the metal perforated the plastic end cap or seal is gonna go away soon and require replacement anyway.  Test & repair, guessing $40ish and no guarantee it won't leak somewhere else.  New rad for $60ish with warrantee.  As for the pump, unless the coolant was allowed to turn to rust it's very unlikely to have an impeller problem.  Look under the pump and you'll find a weep hole, if it's wet or has trails indicating that it has leaked your pump seal has gone.  Being parked a long time it's possible it slowly leaked and may not leak again now that it's being used, but it's probably an indication that it'll go out soon.  Also wiggle the fan to check for loose pump bearings and worn fan clutch.

 

No reason to replace the sender unless it's not working right; if it was indicating cold and the no heat also indicates cold coolant it seems there's no reason to suspect it's bad.  The rad cap is probably bad since you had no pressure, but if the coolant was low when you were checking then the cap may be fine.  As for your Amsoil protection, the head gaskets would probably blow before anything oil related would be damaged no matter what kind of oil you're running.  I don't think it has a code option for overheat, probably only the too cold one.  Without a therm in cold weather it'll stay quite cold, I've seen a few and they wouldn't get to 140 in So.Cal. cold.  Did you do a cold flow check to see if it's stuck open?

 

The recovery bottle can't be trusted on a car that has been parked a long time.  In normal use, assuming the hose isn't leaking or plugged up, it'll be reliable.

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And someone said something about not using a rebuilt pump, only new.  Unless you're buying new OEM you're probably getting a Chinese pump vs. a used OE casting with new internals.  While I've had some castings with damaged threads or other problems that went undetected by the rebuilder, the castings are overall better than new Chinese stuff.  I've also seen where the new pumps have stamped metal impellers and the OE and rebuilt used a cast impeller.  No way for me to know which flows better, but I trust the OE engineers more than a thoughtless penny pinching Chink to design an impeller.  Rebuilds are starting to fade away tho, turns out that a whole new part from China costs less than paying an American worker to replace the internals in an existing casting.

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1 hour ago, superhawk996 said:

Somehow I guessed it was a 3.0, almost scary.

 

I don't see how it's cheaper to test it off the car since there's more work involved, it also won't test the system.

 

Well, I'm doing the work, not the mechanic. ;)  I'm planning on replacing the thermostat and testing with plain water.  If the temperature gets back up, and things work more "normal" I can pretty much rule out a leak in the radiator.  So far, I'm not finding any dripping, so a pressure test of the radiator may not be needed at all.  I'll see about what it would cost to pressure test the system for a leak.

 

1 hour ago, superhawk996 said:

"the shop specializes in radiators and fixed your XX radiator"....you mean the one that was still leaking and had to be replaced???  Yea.

 

I replaced it original one as a preventative move.  It didn't ever "leak" again, and I had the chance to snag a replacement XX radiator cheaper than buying a new one.  I still have it as a spare part...just in case.

 

1 hour ago, superhawk996 said:

If it has sprung a leak in the metal section I would not have it repaired, I'd replace it.

 

A good point.  The current radiator is a replacement one.  Same issue.  Leak too close to the plastic (or in the plastic) so it was safer just to replace the whole thing.

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The 3.0 is a good overall choice.

 

The B2500 series is underpowered, requiring you to rev high and shift late.  B4000 is a bit much if you don't do a lot of hauling.  B3000 gives you enough power to do most anything the truck's designed for without wasting gas needlessly.  I hauled some overloaded shit from Wyoming to Las Vegas and it performed like a champ.  Not much for acceleration, but it was smooth as butter when you needed power to pull.

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I bought a pressure testing kit for just these kinds of circumstances. Will be hilarious if you pull your radiator only to find you just needed a new radiator cap.  Typical do shit the hard way approach and question everyone else's simple logic.

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