overheating?

[dyeager535]

1. Why was there air in the system to begin with? And why didn't my mechanic notice it or purge it properly when he did the thermostat?

This happens. New cars are the ones that really have problems with air getting trapped. Our trucks have the radiator cap as the highest point in the system (outside of the overflow) so air always has an outlet. In an application where the radiator cap is NOT the highest point, air will find the high spot and stay there, which is usually somewhere in the motor. As long as the overflow has coolant, our system will purge itself.

2. The only way I can think of air appearing is if there is a head gasket leak. I need to find this out or it's going to eat at my brain. So, I need to do a compression test? I've never done one, is it hard and is the tool expensive?

If it really bugs you, or you like to play around with tools, go rent the cooling system pressure checker from Autozone (free with refundable deposit), and hook it up to your truck. Once I got all my hoses properly tightened it held 30PSI for over 12 hours. Thus, I verified no leaks.

Agree, it was probably the gauge.

 

[Jessie James]

If it really bugs you, or you like to play around with tools, go rent the cooling system pressure checker from Autozone (free with refundable deposit), and hook it up to your truck. Once I got all my hoses properly tightened it held 30PSI for over 12 hours. Thus, I verified no leaks.

I agree that this would be a simple way to test things, easier than a compression test and should (?) produce the same end result.

If the "pulses" were in sync with the motor revolutions, then I bet it's the head gasket.

 

[British Slave]

How are your heater hoses routed? Do they loop down low on the fender well?

 

[joshkbomb]

I agree that this would be a simple way to test things, easier than a compression test and should (?) produce the same end result.

If the "pulses" were in sync with the motor revolutions, then I bet it's the head gasket.

The pulses were every few seconds. Although I saw a couple before I shut the engine off.

 

[joshkbomb]

How are your heater hoses routed? Do they loop down low on the fender well?

It's pretty much a straight shot from the radiator to the heater core, with a little sag.

 

[Jessie James]

The pulses were every few seconds. Although I saw a couple before I shut the engine off.

I've never experienced a water pump failure, so I don't know what symptoms that might produce. What you describe sounds like what I have seen in head gasket failure.

Get that pressure tester as an easy way to start checking things out. If it won't hold pressure, then do a compression test. The test is simple. You remove all your spark plugs, then screw in this spark-plug adapter connected to a hose connected to a gauge. Then turn the engine over with the key for a few seconds and read the pressure. Move to the next cylinder. Repeat. They should all have a PSI within a small range of each other, say 10-15 PSI.

If your head gasket is blown, you will likely see two cylinders next to each other, on one side, that are both low about 20 (I'm guessing) PSI or more compared to the other cylinders.

The whole test shouldn't take you more than about 15 minutes, unless you have a truck like mine where getting the plugs out is damn near impossible. In that case, consider first removing your front inner fender covers for easier access to the spark plugs.

 

[British Slave]

I've never experienced a water pump failure, so I don't know what symptoms that might produce. What you describe sounds like what I have seen in head gasket failure.

Get that pressure tester as an easy way to start checking things out. If it won't hold pressure, then do a compression test. The test is simple. You remove all your spark plugs, then screw in this spark-plug adapter connected to a hose connected to a gauge. Then turn the engine over with the key for a few seconds and read the pressure. Move to the next cylinder. Repeat. They should all have a PSI within a small range of each other, say 10-15 PSI.

If your head gasket is blown, you will likely see two cylinders next to each other, on one side, that are both low about 20 (I'm guessing) PSI or more compared to the other cylinders.

The whole test shouldn't take you more than about 15 minutes, unless you have a truck like mine where getting the plugs out is damn near impossible. In that case, consider first removing your front inner fender covers for easier access to the spark plugs.

Just want to add. If you do a compression test, be sure and hold the throttle wide open when cranking.

 

[Fordum]

Josh, these guys here have mostly never heard of burping a cooling system. They work on older iron when the guys who were designing it didn't know of a "better" system like the newer cars.

I have had to help burp some of the new stuff by parking at an angle, loosening certain hoses, that sort of thing.
With these, you just fill it, run it, and refill if needed.

I have had two water pump failures that caused symptoms like you described. That is in 40 years of normal failures, so it ain't common.
One, was on my old Jeep. It would run hot at speed, cool off at idle. Normal stuff did not help.
Finally, after a couple of weeks, I was sitting at a red light, and my fan started hitting my radiator.
Got out, and the water pump shaft had slid out of the housing far enough for the fan to hit with no water leakage at all.

I was about two blocks from help, so I just slid it back in and drove it back. Turns out the impeller was loose on the shaft.
At low speeds, it would grip enough to pump, but when you tried to force it to pump faster, it started slipping.

The other one was a little different. It was on a Pontiac. The pump started leaking, so the guy replaced it.
After that, it never cooled right. Faster you drove, the worse it was.

Finally he came to me in desperation.
Standard procedure. If it was working before you did something, and not after, check what you did.
No matter how much you revved the engine with the cap off, I never saw much flow.
I remembered the loose impeller, so I pulled the new water pump off.

I could not turn the impeller on the shaft, but it had a warranty, so we took it back to the store. He agreed to replace it, and asked what it was for, since we did not have the box.
He looked it up, brought out a new pump. We took it out of the box intending to use that box to put the old one in, and it was real obvious that they were different.

Housing was the same, fan mount was the same, but the impeller was totally different.
As soon as I saw it, I realized that the other one was wrong, It was much smaller than the hole.
He checked a few others in stock and they all had the same impeller.
Only the one he got first had the small one. It seems that the rebuilder had pressed on the wrong impeller, or it was for a different model car.
Replaced it, and all was well.

 

[joshkbomb]

You guys keep talking about how I don't need to do what I did to get the air out of the system (running it with the radiator cap off is burping?). But the air never got out on its own, which was my problem. Is there something that could go wrong with clearing out the air from the system?

I'm going to do a cooling system pressure test and then possibly a compression test to rule out or confirm a head gasket. If those come back negative, I'll just start replacing parts till I find the culprit. If it is the head gasket, then I'll probably have a new engine in my future given how many miles are on this one (250K).

 

[dyeager535]

You *should* be able to test head gasket with the cooling system checker as well.

Pull all the plugs before pressurizing system. Pressurize system. If head gasket(s) leak, the pressure gauge will show drop in pressure, and cylinder(s) will fill with fluid.

I've not tested enough motors this way to know for sure, and I assume something like a small crack in a head MIGHT not leak on a cold motor with 30PSI, but I would *expect* something like a blown head gasket to result in coolant in the cylinder.

 

[4X4HIGH]

You *should* be able to test head gasket with the cooling system checker as well.

Pull all the plugs before pressurizing system. Pressurize system. If head gasket(s) leak, the pressure gauge will show drop in pressure, and cylinder(s) will fill with fluid.

I've not tested enough motors this way to know for sure, and I assume something like a small crack in a head MIGHT not leak on a cold motor with 30PSI, but I would *expect* something like a blown head gasket to result in coolant in the cylinder.

That test won't do any good if the head gasket is blown between a water passage and an oil return as then he would have water mixing with oil but not getting into a cylinder.

 

[dyeager535]

So you are saying check dipstick before and after pressurizing coolant system as well.

 

[joshkbomb]

I don't seem to have any oil/coolant mixing going on (checked again this morning). Just possibly exhaust.

I think the overheating might be coming back. Yesterday it went a bit over 210 once and today it went up to 230 or so a few times. Although it did spend 90% of the time at 200. If there's more air in there, I don't know where it could be coming from except for the head gasket. If I don't get around to the pressure test tomorrow night, I will this weekend.

I measured the temperature of the block next to the temperature sender today when the temp gauge read 200, the block read at 200. A couple days ago when the gauge read 260+ I measured 240 on the block in the same spot. Originally I thought this was due to being near the exhaust manifold and ignored it. But, I now think this means my truck was really getting that hot and it wasn't just the gauge.

 

[dyeager535]

You can run the pressure test to see if you find a problem there, but based on what you've said, it sounds like the coolant isn't moving efficiently. The temp difference across the radiator makes it appear the radiator is working ok. But the only reason I can think the radiator would show that drop, WITHOUT the engine cooling properly, is because the coolant isn't moving out of the radiator.

Since you say the coolant temp (measured on the hose) starts at 190*, but drops to 125* before it reaches the radiator, I'm going to say the coolant just isn't moving through the hose either.

I don't have nearly the experience with these motors as others here, but I do have a buddy that has torn up a few waterpumps using a flex fan on a race motor, pulling the shaft out the front of the pump as someone else here mentioned had happened to them. If the radiator was rotten, (and I've only seen this happen on a Ford) I wonder if the impeller blades aren't rusted away? Assuming this is the same pump that worked fine at some point in the past, we can't assume you got the wrong water pump or anything of that nature.

 

[Fordum]

You also need to do an exhaust gas test on the radiator.

I don't know why nobody seems to do this anymore, but every radiator shop in town used to do it on every car that came in to eliminate a head gasket problem from the start.
Its a small kit. If you have a rad shop in town, give them a call and see if they will do it and how much.
Or you might find someone here close by who has one.
I have been suggesting it for a while now, and I know some have either bought them or found a rental somewhere.

Its a cap that fits on the radiator, a small hand vacuum pump and some liquid.
You hook it to the rad, suck some air out of it and it bubbles through the liquid. If there are combustion gases in the rad, the liquid turns color.

I hate throwing parts at one, but you might consider a water pump at this time. Either pull the one you have and examine it, or replace it.
By the time you get the old one off, you might as well put on a new one.

Check with others here who have the same type setup as you to be sure, but most engines you can rev the engine with it warm and the cap off and see the water level in the rad drop for a second.
That would tend to indicate that the pump was pumping.

 

[Jessie James]

Fordum just reminded me of another odd issue I've seen once, again in about 40 years of working on cars:

You may have a replacement water pump with a cheap impeller.

A long time ago I had an overheating problem and removed the water pump. Instead of a nice cast impeller, which fit into the housing nicely, it was a piece of sheet metal (of sorts) that was stamped, cut, and bent to make a "fan" blade. Well, since this did not fit into the housing, at high speeds the "blades" would just churn up the water. At that point, the water would start to boil, and voila, now you have air in your system.

Thinking about that, I would still do the pressure test because it's (a) cheap and (b) easy. If that comes back okay, remove the water pump.

Your pump should NOT look like this one (blade on the left):

and SHOULD look something like this:

Can you see how the first one would not work?

 

[joshkbomb]

You also need to do an exhaust gas test on the radiator.

I don't know why nobody seems to do this anymore, but every radiator shop in town used to do it on every car that came in to eliminate a head gasket problem from the start.
Its a small kit. If you have a rad shop in town, give them a call and see if they will do it and how much.
Or you might find someone here close by who has one.
I have been suggesting it for a while now, and I know some have either bought them or found a rental somewhere.

Its a cap that fits on the radiator, a small hand vacuum pump and some liquid.
You hook it to the rad, suck some air out of it and it bubbles through the liquid. If there are combustion gases in the rad, the liquid turns color.

I hate throwing parts at one, but you might consider a water pump at this time. Either pull the one you have and examine it, or replace it.
By the time you get the old one off, you might as well put on a new one.

Check with others here who have the same type setup as you to be sure, but most engines you can rev the engine with it warm and the cap off and see the water level in the rad drop for a second.
That would tend to indicate that the pump was pumping.

It looks like Autozone rents one of those testers out:
http://www.autozone.com/autozone/accessories/OEM-Block-Tester/_/N-25dh?itemIdentifier=391378_0_0_
I'd have to buy $8 worth of fluid for it, but then it would save me having to pull all the spark plugs to do the cooling system pressure test. Is this as definitive?

My water pump has over 60k miles on it at this point, so it's probably time even if I get things worked out.

 

[joshkbomb]

It looks like the first one would just push the water creating boiling (or cavitation?) instead of the second moving the water more "gently".

I never skimp on parts, so if I do replace the water pump it will be whatever the best one at Napa is (which presumably will look like the second).

 

[joshkbomb]

Wait, I just read over the posts again. Do I have to pull the spark plugs for the cooling system pressure check or is that just the compression test?

 

[British Slave]

There is no need to pull spark plugs for a cooling system check.