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Kia Sedona 2.9TDi Year 2000
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Discussion Starter #1 (Edited)
This is not for the faint-hearted. My apologies for the length of this. I didn't want to miss out any of the observed symptoms in case they might help. I know that you may just see the description in the title and respond with "Cylinder Head Gasket" but I am interested in acquiring understanding. So here are the details:

Kia Sedona 2.9TDi 2000

The first symptom was a loss of warm air from the heater and the engine temperature was fluctuating from the middle of the gauge down to cold. So, I replaced the thermostat and that sorted out the fluctuation and cold temperatures. I filled it with water and that gave me heat inside the car again. But then, I was losing lots of water. I would travel for half an hour and lose about 1 litre of water. It was very difficult to locate the source of the "leak" but eventually I tied a little plastic bag over the overflow pipe coming from the expansion tank and I found that it filled with coolant. Initially, when the engine is cool nothing goes into the bag but it does blow up like a balloon. It only starts to fill with coolant after the engine has come up to the normal operating temperature.

So, I felt that this must be a blown cylinder head gasket, or a cracked head (woe betide).
Now, I actually have some (limited) repair insurance with the AA, so I called out the AA and the patrolman immediately suggested that it was probably a head gasket. I then had to take it to a garage to get a definitive diagnosis so that the AA could authorise a repair. They tested the air-tightness of the water system: they removed the radiator (not actually on the radiator) cap and used a device to pump up the water system to about 15psi and then the pressure gauge on the device showed it losing pressure very quickly. They found that the pipe (about an inch in diameter) that goes from the (radiator) pressure cap housing (containing the thermostat) off towards the heater matrix, had sprung a small leak which was resulting in some hissing. They tightened the jubilee clip around the end of that pipe where it met the pressure cap housing. When they tested again, the coolant system was holding steady at 15psi with no leakage.

After that, I didn't manage to get the coolant to overflow from the expansion tank. However, there were bubbles coming through into the expansion tank, so they tested these gases by removing the pressure cap again and putting a device into that housing that allowed these bubbles to pass up through a purple liquid. This was supposed to detect any carbon monoxide by turning yellow. Despite having gas bubble through it for ages, it did not detect anything. So they concluded that the cyclinder head gasket must still be intact. So presumably we must have been looking at air pockets gradually passing out. When we revved the engine the bubbles slowed down. So, my only problem with this conclusion is that I have never seen coolant coming out of the expansion tank while the car is stationary. This gas test was done while the car was stationary. But would we not expect some of these trapped gases to have contained some exhaust gases?

So, I bombed up and down the motorway for about half an hour and I still didn't get any further coolant overflowing. That really surprised me.

So, why would that jubilee clip have resolved that problem. I developed a theory whereby, the coolant would expand when hot into the expansion tank and then when it cooled, it would suck that coolant back into the system, but if it had an air leak then maybe it would just fill with air instead, so that when it heated up next time it would push coolant out of the expansion tank because the volume of coolant and air would now be larger.

Unfortunately, I have now come to use it again and this time coolant has overflowed out of the expansion tank again.

Finally, here is my general reasoning. I have had the experience of topping up my coolant at the top of the engine where the pressure cap is and making sure that my expansion tank is below the maximum line, and then going for a drive and finding that it had overflowed. Now, the only reason I can see for it overflowing is if gas is entering the system. The expansion tank should have enough space for the coolant. Considering the coolant should be under pressure, I don't think that the additional gas could be air because that is at lower pressure, so I can't see how that would get into the pressurised system while it is running. So I can only see high pressure gas entering from the cylinders.

Can anybody help me with their greater understanding?
Thank you
 

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Cerato
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692 Posts
I think that your reasoning is sound.

How does the car perform? Any fluttering sounds that suggests a bad cylinder? Any sign of water in the oil?

You could try a compression test on the engine.
 

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Kia Sedona 2.9TDi Year 2000
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Discussion Starter #3
The car performs perfectly well. It doesn't have any problems when cold. There is no sign of water in the oil.
How would a pressure tester be used? My Dad has one but he said that he would want to put it down where the glow plugs are. But there aren't any glow plugs...and he thinks that using the injector apertures would be difficult because the injectors are just push fit.
 

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Kia Sedona 2.9L CRDI 2005, Yamaha FJ1200 1986
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hi mine is the same 55plate 2.9L, 97k on the clock, i lost 1.5litres of coolant somewhere??? topped it up and every 2 or 3 days i have to top up again.... i did notice the large hose from the radiator to the thermostat housing is nice and soft when the car is cold but as it heats up the pipe gets harder. when i bought this it had no heater pipes to the rear so it had already failed, i repaired this with copper pipe and heat is good in the back. i thought gases were getting into my system so i bought real steel and put it in the system, this has helped reduce the pressure in the pipe from the radiator. i have been parking it nose down and when i switch off i usually hear it gurggling in the back. i have now been parking nose up and all gurggling has gone so it was obvious i had an air pocket in there. i am still however losing a little coolant every week but there is no signof it under the car.....i am still investigating this.. :(
 

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Kia Sedona 2.9TDi Year 2000
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Discussion Starter #7
I am now losing lots of coolant. It is clearly bubbling through quite fast.
I have now done some compression tests on the cylinders and found that they are all reading between 300psi and 310psi.
Bearing in mind that when the garage tested the bubbles, they did not seem to be combustion gases, and that I don't appear to have a compression problem, where is all the gas coming from?
Is there anybody out there?
 

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Cerato S Hatch Auto
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When you say that you are losing lots of coolant, did you refill and top-up with "anti-freeze" or just water? If you only have water in there, perhaps it is just boiling off? Ethylene Glycol in coolant extends the operating range of the coolant in each direction. (i.e. It's anti-boil as well as anti-freeze).

Might be an idea to check that the radiator is not partially blocked. This would lead to boiling.
 

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Kia Sedona 2.9TDi Year 2000
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Discussion Starter #9
Thanks for the suggestion. What is the best way to check to see if my radiator is blocked?
 

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Cerato
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Thanks for the suggestion. What is the best way to check to see if my radiator is blocked?
Normally you take the radiator off the car and use a hose to flush it. Flush in both directions. Only experience will tell you if the flow is adequate.

Easier to do this if the radiator is off the car; less chance of (dirty) water getting where it shouldn't.
 

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Kia Sedona 2.9TDi Year 2000
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Discussion Starter #11 (Edited)
I've just been thinking about this a bit more. If it were a blocked radiator and boiling the water, I would expect to have seen some steam, right? None of these bubbles look like steam to me, and I get the bubbles immediately when I start my engine from cold. Also, my car is not overheating, according to the temperature gauge.
 

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Kia Sedona 2.9TDi Year 2000
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Discussion Starter #12
So, to summarise the symptoms:

1. Bubbles in my expansion tank
2. Bubbles where my radiator cap is (once removed), immediately as I start my engine from cold. (The bubble do not appear to be steam.)
3. Coolant overflowing from the expansion tank. I lose about 1 litre in 10 miles of driving when the car is warm.
4. No coolant overflows when the car is stationary with the engine running, even if I rev it up high.
5. The bubbles have not registered as combustion gases using the test kit.
6. No overheating, according to the temperature gauge.
7. Compression tests have given 300psi-310psi on all 4 cylinders.
8. When applying 5bar compressed air to the cylinders, no bubbles appeared in the coolant.
9. No steam from the exhaust.
10. No trouble starting in the morning.
11. The car runs perfectly normally. Acceleration and power are normal. Fuel efficiency is normal.
 

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2001 Kia Carnival 2.5L manual & 2000 Carnival Auto
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Just a suggestion, replace your radiator cap.
Also check for the notorious leaking pipes traveling to rear heater.

Suggest you travel over some dusty roads, then inspect underside of vehicle for any wet/muddy spots around tubing...
As it may be a slow leak that only opens up when hot..
 

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Kia Sedona 2.9TDi Year 2000
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Discussion Starter #14
Thanks for your suggestions.
I have already changed my radiator cap, but this can't be the cause of the bubbles. They appear before they arrive at the cap.
I have already short-circuited the rear heater pipes beyond the front section.
I'll be very lucky to find a dusty road at this time of year. I notice you are from Australia - plenty of dust. But, to be honest, I know where I am losing water. The question is where I am admitting gas into the coolant system.
 

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Greetings,

Using blue-colored paper "shop" towels are also really handy for detecting leaks from the coolant system - the towel turns a dark blue, when liquid is on it..

SCOTT Shop Towels, Roll, 10 2/5 x 11, Blue, 55/Roll, 30/Carton: Amazon.co.uk: Car & Motorbike

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I would carefully inspect all hoses, even a -small seal leak- will emit lots of coolant when the vehicle gets hot / to temperature.

Any soft hoses should be scrutinized and/or replaced,

Any rusted clamps should be replaced w/ new hardware,

in addition to removing the hoses & inspecting the connector ends, making sure there is no material inside the mating portion of the hose that may be acting as a leak path,

and using fine-grit sandpaper and/or fine steel wool to clean up any scale/corrosion on the mating surfaces as needed,

The coolant drain in the bottom of the radiator should be inspected: if tight, I would release a small amount of coolant to lubricate the rubber seal around the drain plug, and re-tighten (hand-tight / firm only),

* You should be using the recommended 50/50 mix of anti-freeze and distilled water recommended for your Sedona ..

If cleaning up hose connections & Q/A'ing -> re-tightening the radiator drain plug doesn't solve it, then I would consider & investigate the radiator, and water pump, as possible causes next..

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I hope this helps,

Regards,
GottaCruise
 

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Kia Sedona 2.9TDi Year 2000
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Discussion Starter #16
Thank you for your suggestions
How can air be admitted into the water system when the water system is under pressure?
Thank you
 

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Thank you for your suggestions
How can air be admitted into the water system when the water system is under pressure?
Thank you
You are losing coolant under pressure - air is being sucked back in to equalize the system / the displaced coolant,

Suggest you re-check the thermostat first, pull the thermostat, heat some water to > the opening temp., and place the thermostat in the hot water to make sure it is opening fully and evenly.

Gloves are recommended, kitchen tongs are handy to remove the thermostat and check it..

When cool, reinstall, making sure the metal (spring) portion of the thermostat is in the direction of the heat source (motor).. The thermostat s/b marked w/ direction of coolant flow, the spring portion that opens the thermostat should be pointing towards the motor.


You have (2) radiator caps (old and new), compare the Open PSI and make sure it matches what the system is rated for..

** Re-check the radiator, get a flow test done like Dr. Bob suggested,

** Purchase an InfraRed (IR) thermometer so you can more accurately determine:

The temp. at the thermostat outlet (where the top radiator hose connects to the motor),

The temp at the top radiator hose inlet,

The temp at the bottom radiator hose outlet.

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You stated above the heater core was disconnected, where the (2) hoses going to the heater core (plugged) or properly (bypassed) ?

** If plugged and NOT bypassed, you may have omitted coolant from the engine, install a proper bypass using some hose connectors and a length of heater hose ASAP..

After you have verified the thermostat / that the system / hoses are hooked up or bypassed properly, place a piece of carboard under the vehicle, and run the vehicle until hot, this may take up to 1 hour or more.. Use the IR thermometer to closely monitor the temp at the thermostat outlet, DO NOT RELY ON THE TEMP GAUGE ON THE DASHBOARD.. Shut off, let cool some, and check the carboard for any coolant -> start tracing to find the leak.


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Does your vehicle have an electric fan? Is it working properly?
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If equipped w/ a diagnostic port, consider purchasing a scanner so you can see the real-time value of the engine coolant temp. sensor and compare the value against the IR thermometer reading at the thermostat housing..

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Make sure you are purging all air out of the system when refilling coolant, this involves running the motor with the radiator cap off until hot / thermostat open, and topping off the coolant level in the radiator.. Shut the vehicle off, Make sure the overflow/expansion tank is filled to the MIN level, and squeeze the top radiator hose (wearing gloves/hand protection) to "burp" the system / force any trapped air into the radiator.. Top off w/ coolant as needed.

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If the vehicle is overheating after (x) miles of driving, warm up the vehicle, drive 1/2 that distance, park, let the motor / cooling system cool down, and check the expansion tank level / and the radiator level.. Top off and try again.. (See above, trapped air in system),

If there is an air purge valve at the thermostat housiing, open it slowly to release any trapped air, close, and top off the radiator and expansion tank to the MIN level w/ coolant,

If no joy above..

*If the flow test on the radiator is good, consider the water pump suspect..

*If you do not have a service manual, consider getting one: I wouldn't be working on my vehicle without one.

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Regards,
GottaCruise
 

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Kia Sedona 2.9TDi Year 2000
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Discussion Starter #19
Thanks for your suggestions - a lot to test.
I would still like to have explained how any of these possible faults would explain why I only lose coolant while it is moving. The other tricky one to tie in is that the garage could not detect any CO2.
 

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2001 Kia Carnival 2.5L manual & 2000 Carnival Auto
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do another coolant system pressure test
Gottacruise is correct.
Especially given your earlier hose clip fix.

Air gets sucked back into the system as cools down.This then rises and bubbles out as engine warms/pumps coolant. That air forces coolant out into expansion bottle in spurts.

you never indicated earlier that already replaced pressure cap,
nor that bubbles were visible at radiator fill point when cool.

check for dusty, blistered hoses (they delaminate), or strong glycol smell when hot engine, any loose hose joints onto pipes or fittings..
loose engine welch plugs can do it is well, but uncommon.
I reinforce the statement that it takes very little fluid loss to cause lots of bubbles.

Do another radiator pressure test
 
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