Overheating or just bad flow???

[jvilla]

So, my radiator has recently started boiling over, but not overheating... I think. After the symptoms started, I replaced the thermostat and coolant temp sensor just to make sure it was working correctly.

-new thermostat and temp sensor
-new coolant
-when the engine gets up to normal operating temperature, the temp shoots to the middle of the gauge and then slowly goes back down to closer to the "Cold" side. I think this is when it boils over.
-top radiator hose gets very warm to the touch.
-radiator cap doesn't get hot at all. It is sometimes cool to the touch while the engine is running at normal temp.
-faint gassy smell in coolant. also some weird foamy grey substance (oil maybe)

Is this a double whammy situation of bad water pump AND head gasket leak? Anybody ever have these symptoms?

 

[jvilla]

Oh yeah, 1989 Bronco II 2.9L

 

[Tedybear]

Sediment in the coolant is normal. Even with the best rust prevention chem's? It still happens inside the system. That's why we do flushes and refills on a schedule.

When you say it boils over---is it actually spewing out the system into the coolant jug in a violent fashion? It is normal for the system to 'purge' out some coolant when it's at temp and under pressure---and to 'draw' coolant in from the jug once things cool off. But it shouldn't be a violent type of dumping.

http://www.ehow.com/how_7885485_test-exhaust-gases-coolant.html

I suggest doing the kit and seeing what's going on from that point of view.

I've got a 2.9 in our '89. So keep us posted. We had to replace both our heads due to cracks--and this website kicks tail when it comes to people helping out!

S-

 

[RonD]

Could be head gasket, could be heater core.

Is the heat in the cab not as hot as it used to be?
On some Fords the heater core is part of the cooling system, if the core is partially blocked the engine temp will go up and down almost randomly.
All you need to do is to look in the engine compartment, if the two heater hoses run from the engine to the firewall(core) without any sign of a heat control valve or 4 hose by-pass valve then your core is part of the cooling system and could be the problem.

If this is the case the core is usually cheap and easy to replace, but for now you can just by-pass the core.
Either remove both hoses from the core(firewall) and connect them together, or remove one hose completely and run the other hose as a loop between the two engine connections.
So take the core out of the loop and see if engine temp behaves normally.

If there is a 4 hose by-pass valve that could be the problem, by-pass the by-pass valve, lol, and see if engine temp behaves normally.



The head gasket can also be easily tested with a latex glove or plastic baggie.
With engine cold remove rad cap and overflow tube.
Start engine.
A vehicle cooling system has no internal pressure when cold, the pressure comes from coolant heating up and expanding, after 5 minutes usually, the water pump just circulates coolant it doesn't pressurize anything.
After starting,
If rad starts to over flow then you may have a head gasket issue, pressure from cylinder firing is coming into the cooling system(via head gasket) and displacing the coolant in the head and overflowing the rad cap opening.
No coolant coming out, then lets test for pressure
Place glove or baggie over rad cap opening and pinch it tightly to seal it, rubber band works too.
Place finger over overflow outlet on rad cap opening, system is now sealed
If glove starts to inflate you got a head gasket issue, or.....cracked head.
If it stays deflated then life is good look else where for the problem.


Lower rad clog can act similar, when t-stat is closed coolant circulates in the engine(and heater core on some ) when t-stat starts to open the flow is transfer to the rad for extra cooling, if flow thru the rad is partially blocked engine can not be cooled as it should.
If a rad is partially clogged you can sometimes tells by feeling the upper and lower hoses.
Upper hose is coolant that is coming from the engine so will be hotter than lower hose, lower should be only 10-20 degrees cooler, not a lot cooler.
Also check pressure on hoses, upper and lower should be almost the same pressure, squeeze them.
If lower is way less pressure then rad is clogged.

 

[jvilla]

We had to replace both our heads due to cracks--and this website kicks tail when it comes to people helping out!
S-

Ditto! The coolant if filling up the coolant res and spilling over the top. I'm losing up to half a gallon of coolant every time I drive the car. I was out of town for a few days driving my wife's new car, and she was driving the Bronco and having to refill the radiator, so it has definitely become an issue > But when it does overflow, I would characterize it as violent.

Thanks for the terrific response, RonD! I will do the glove test hopefully later today, but I am starting to suspect the heater core. When I recently flushed the system it was a bit hard to get water through there. I thought it was because the water tubes are a lot narrower than the radiator, which was flowing fine. I don't think the heater core has a bypass. I didn't see anything like that when I was checking under the dash the other day. It looks like the two hoses just connect directly to the inlet and outlet of the core itself.

Is there a good way to test the water pump with it still in the vehicle?

 

[PetesPonies]

maybe I missed it . did you check the operation of the radiator cap?? When they go bad they allow the cooling system pressure to get out. You think you have a problem but it's just a cap that needs replaced.

 

[RonD]

Water pumps are hard to test in the vehicle, if you let engine warm up you will feel the t-stat open when the upper hose gets warm quickly, feel the lower hose it should start to warm up as well and fairly quickly, that usually means rad isn't blocked and water pump is circulating well.

And for the more adventurous, lol, you can rent handheld mini-snake cams now for about $25, and usually you can remove the lower rad hose from the water pump and visually inspect the impellers.

And yes I would replace the heater core, on my '94 ranger it took about 20 min., core was $28 if I remember correctly, up and down temp gauge went away.
This was after I replaced the t-stat and fan clutch, lol, nice to know I have backups, used, but still working backups.

Yes rad caps can fail, either not holding pressure or not returning coolant when engine cools(collapsed rad hoses), often a good practice to replace them every time you change the coolant.

 

[PetesPonies]

Not closing and not allowing return coolant is the same fail. They loose pressure at the seal. They can be tested easily with the proper tool. Water pumps basically don't fail as far as circulating fluid. Over 35 years of working with cars, never have removed a pump where the impeller was bad. I only have seen pictures in text books I used to show my students It's possible but oh so rare.

 

[RonD]

Not closing and not allowing return coolant is the same fail. They loose pressure at the seal. They can be tested easily with the proper tool. Water pumps basically don't fail as far as circulating fluid. Over 35 years of working with cars, never have removed a pump where the impeller was bad. I only have seen pictures in text books I used to show my students It's possible but oh so rare.

Well not really, a rad cap has two separate spring "valves", out and return.
Nice video on it here:
http://www.youtube.com/watch?v=0JdDWWoX-70

Electrolysis can eat impeller blades, I notice it more on the after market water pumps, cheaper metal in the blades I would suppose, and foreign cars, serves them right, lol.
And on aluminum head cast iron block engines more, not sure why that would be, bi-metal I guess helps it along.
But yes very rare since none of that happens if coolant is changed when it should be.

 

[PetesPonies]

Ron I'm not disagreeing with a two function valve, I certainly know how they work. But here is my logic. When the outer main seals goes, the inner part isn't going to work either. And it has been in my case, that most times it is the larger main seal that goes and causes problems. When a person is puking coolant, it's the main seal that has given up the ghost. If you ever had a situation where your radiator was just a bit low, but your reservoir had coolant in it . . then the small inner seal is the problem. Much rarer I believe. Bit in both cases, same answer . . get a new cap. I bet most places like Autozone can test your cap for you. I have my own tool, so I don't know that for sure . . but I'd certainly ask if I were the poster.

 

[jvilla]

Update:

Unhooked heater core: no change
New Radiator cap: no change
new heater hoses and upper radiator hose - very small leaks in both and replaced for good measure.

I did the glove test as suggested by RonD, but I apparently don't have a head gasket leak! Yey, that's good news. And the water pump *seems* to be working fine, buy am not positive. When I step on the gas with the radiator cap off, I can see something happening in the opening. Sometimes coolant spews out when I really rev it up.

Only other thing I can think of is blockage in the radiator itself or perhaps the water pump is bad after all...

Stay tuned for another episode of the non-overheating but nonetheless cooling problem plagued Bronco II.

 

[PetesPonies]

Of course the water pump is working, thats the point I was making.

Now, let's be clear. You replaced the cap and the hoses. But you are still pushing out coolant right? And when and where? While it is running but still? Out the overflow ?

 

[jvilla]

The coolant is overfilling the reservoir then coming out of the top of that and, it seems, when pressure gets to high because it is overfilling the res tank, comes spewing out of the rad cap.

I guess the question now is, why is the coolant overfilling the res tank? I think there could be blockage in the radiator that is making it hard for water to return to the engine.

 

[PetesPonies]

When the pressure is too high, the cap releases and lets the coolant go to the tank. It's overfilling the tank because it keeps coming out of the radiator, which means it is really overly hot or you are pressurizing the cooling system. So what do we know about the head gasket? nothing right? Because you can pressurize the cooling system by way of a leaking gasket; leaking into the cylinder. This doesn't have to show up as an internal leak. How long does it take for the radiator to start kicking out coolant?

 

[jvilla]

5- 10 minutes... of course depends on the weather outside and how I'm driving it. But basically when it warms-up. It's been anywhere from 25-65 degrees outside the last week and a half, so it's kind of hard to say.

NEW INFO: While running the engine, the upper rad hose is VERY hot to the touch while the bottom is significantly less hot. More than the 10-20 degree difference expected.