Trying to understand my coolant system pressure test results

[mpk]

I hope someone can help me understand the meaning of these results.

I connected a pressure tester to the overflow tank.

- With car off, pumped to 15psi. It takes 5 minutes before it is slightly lower than 14 psi. So a very slow drop in pressure. I can find no visible leaks.

- With tester connected and pressure gauge at zero I turn car on. No movement in gauge. Okay, I pump it up to 15psi. At 15 psi, the needle remains steady on the gauge but it very very slowly rises in pressure and after several minutes I am up past 16 psi. I release pressure back down to 15 psi and then it eventually starts climbing again very slowly. Minutes later I am over 16 - 17 psi.

If I step on the gas, the pressure in the gauge drops and then goes back up. The pressure increases slightly more by doing this.

Are these normal readings or is this indictive of a head gasket leak? thx

2007 Torrent AWD, 6 cylinder.

 

[melsg5]

The coolant is heating up and there is no relief valve which normally would be the pressure cap, so the pressure is going to rise.
Did you use the tester on the pressure cap?
You should also buy a coolant hydrocarbon tester if your checking for a blown head gasket.

 

[mpk]

A mechanic said he put a new cap on awhile back but I tried testing it anyway. Is it supposed to hold pressure? I pump it up to 15psi and it drops back down quickly, then very slowly and slower. Was going to buy another one tomorrow.

As for the dynamic test with the tester connected to the overflow I thought when you step on the gas it should not effect the gauge? But it does, it drops down when stepping on the gas then goes back up when I let my foot off the gas.

I did buy a Lisle 75500 Combustion Leak Detector with fluid but I did not have a vacuum. It says you can use the engine vacuum but I do not see one. I tried a turkey baster as suggested elsewhere online and the color did not change of the fluid. But I am not sure how accurate this test is doing it this way.

btw - I ended up doing all this because of over heating in traffic or stop lights. Antifreeze would get pushed out of the overflow tube making a mess. Re-burping the system and letting the air out of the overflow temporarily takes care of it. I replaced thermostat, even taking it out for awhile at one point, replaced temp sensor and temp sensor cables, been flushed and bleed many times. Used a garden hose on everything to be sure there was no blockage anywhere including radiator and heater core). Sometimes when it starts to overheat I can bring the gauge down by stepping on the gas while waiting at a light, but not always and have to pull over, open the overflow ever so slightly to let the air out so I can drive again)

 

[melsg5]

The cap is supposed to hold pressure.
So based on your test it fails.
In addition you make no mention of fan operation.

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[mpk]

But what do you think about my test results, like pressure gauge dropping when gas pedal is pressed and then going up higher when I let my foot off?

The fans are operating and go high speed when the temperature gauge is way up.

I am not sure if it is a problem with my tester when it comes to the cap. The new one coming on order would be the second new cap so I am skeptical.

btw - just noticed a noticable click coming from the area of the cooling fans, like every 30 seconds but no change in speed.

 

[melsg5]

Never heard of running a pressure tester on a running engine since there is no pressure relief. Higher engine speed water pump spins faster better cooling and when you take foot off pedal pump slows, heat and pressure go up.

 

[mpk]

I used a Mityvac MV4560 Pressure Test Kit. According to the instructions the dynamic test is performed with the engine running. But the manual only speaks of rapid increases. I got the idea of stepping on the gas during the test from youtube videos on pressure testers, with one guy reving the engine and then claiming there is no head gasket problem. But I am not sure how accurate what I saw is and whether my results indicate where my problem is.

Dynamic Pressure Test (Engine On) - Mityvac MV4560 User Manual [Page 8]

Mityvac MV4560 Manual Online: Dynamic Pressure Test (Engine On). For diagnosing: Cooling system leaks Cylinder head damage Set-up & Procedure: 1. Ensure the cooling system is cool and not pressurized. Carefully remove the radiator or coolant bottle pressure cap (Fig. 6). 2. Check to...

www.manualslib.com

8. Start the vehicle engine and monitor the pressure gauge

An immediate and rapid pressure buildup is an indication of a breach between a cylinder and the cooling system, most likely due to a blown head gasket. Immediately turn off the engine and release the pressure in the system by pressing the Pressure Relief Lever located on pump (Fig. 10). Dis-connect the test equipment and replace the head gasket.

If no immediate or rapid pressure buildup is indicated, operate the pressure pump to bring the system to normal operating pressure. If the needle on the pressure gauge
vibrates rapidly, this is an indication of a smaller compres-sion or combustion leak into the cooling system possibly caused by a damaged block or head. Turn off the engine,
carefully release the pressure in the system by pressing the Pressure Relief Lever located on pump (Fig 10).

Disconnect the test equipment and consider replacing the head gasket

I do not want to replace the head gasket and find out it is the intake manifold.

The exhaust looks normal to me and so does my dip stick. Starting the engine it sounds like a little louder than normal in the exhaust sometimes.

 

[melsg5]

Did you get a new AC-Delco or Stant cap?

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[mpk]

Does it matter?

Was thinking of buy a cheap new overflow tank with cap just to rule it out.

I ended up connecting a garden hose to the overflow connected to a milk jug. Lost more than a half gallon into the jug after I drove and thought I bled it.

 

[melsg5]

The list price for the OEM cap is about $18.
NAPA sells an aftermarket cap for about $10.

 

[Baliguy]

It kind of sounds like you need a real good flushing. It sounds like your radiator is plugged up. That would explain all of it. The Dexcool only works until air gets in, then it gums up. Use a different coolant after the radiator gets cleaned out. I had a fall time ritual of flushing and back flushing my heater core until I switched to Zerex. It is a real pale yellow. It has been great for a few years so far. No more gurgling sounds from the dash anymore too. I flushed out the Dexcool repeatedly with water and automatic dish wash soap. A few flushes with distilled water, then a full jug of Zerex. I checked it with a antifreeze tester. It was a little bit too much water, but still ok freeze wise. Best thing I ever did for the cooling system.

 

[mpk]

I ran a garden hose through the radiator and water was coming out fine the other side.

Anyone have info on whether my pressure test results are normal?

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[melsg5]

Did you buy another pressure cap and test it?

 

[mpk]

Did you buy another pressure cap and test it?

2nd new cap is a Stant cap. Bled air out of system manually burping it. Drove for about 20 minutes and it overheated. Threw more than a half gallon into my rigged up jug connected to the over flow tube , overflowing and spraying everwhere.

Could hear high speed fan when overheating so it appears to be working. Oil cap and oil stick look fine.

The only test that does not seem right is needle movement on gauge when stepping on gas with pressure tester pumped up to 15psi.

 

[MarkEggert]

I hope someone can help me understand the meaning of these results.

I connected a pressure tester to the overflow tank.

- With car off, pumped to 15psi. It takes 5 minutes before it is slightly lower than 14 psi. So a very slow drop in pressure. I can find no visible leaks.

- With tester connected and pressure gauge at zero I turn car on. No movement in gauge. Okay, I pump it up to 15psi. At 15 psi, the needle remains steady on the gauge but it very very slowly rises in pressure and after several minutes I am up past 16 psi. I release pressure back down to 15 psi and then it eventually starts climbing again very slowly. Minutes later I am over 16 - 17 psi.

If I step on the gas, the pressure in the gauge drops and then goes back up. The pressure increases slightly more by doing this.

Are these normal readings or is this indictive of a head gasket leak? thx

2007 Torrent AWD, 6 cylinder.

I just went through all this with a 2008 Torrent I recently purchased. It turned out to be the head gasket failure in the typical place between the #2 cylinder and the coolant passage. Get a "Block Tester Combustion Leak Test Kit" online. It tests the overflow tank for presence of exhaust gasses. It's not expensive - about $35. I replaced the gaskets myself. It's quite an involved job but if you're mechanically inclined it's not that bad a job. There are good videos showing exactly how to do it on YouTube. Good luck!

 

[mpk]

I just went through all this with a 2008 Torrent I recently purchased. It turned out to be the head gasket failure in the typical place between the #2 cylinder and the coolant passage. Get a "Block Tester Combustion Leak Test Kit" online. It tests the overflow tank for presence of exhaust gasses. It's not expensive - about $35. I replaced the gaskets myself. It's quite an involved job but if you're mechanically inclined it's not that bad a job. There are good videos showing exactly how to do it on YouTube. Good luck!

Thanks for the info. I did buy a Lisle 75500 Combustion Leak Detector with fluid but I did not have a vacuum. It says you can use the engine vacuum but I do not see one. I tried a turkey baster as suggested elsewhere online and the color did not change of the fluid. But I am not sure how accurate this test is doing it this way.

I guess the next step is to buy a combustion tester and perform on each cylinder.

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[MarkEggert]

Are you experiencing engine overheating? When I first purchased my Torrent in March I knew it had issues but I also got it for a real good price. It seemed to run fine and on the test drive it drove normal. About a mile from my house on the 12 mile drive home the temp gauge became very erratic. At this time I didn't know that two needle's widths below half on the gauge was normal. When it started overheating the needle would go up to about 3/4 and then back down, back up, but with quick movements. At first I thought it was a bad gauge or temp sender. When I got home I checked the coolant in the overflow tank and it was down about an inch below the split line which is the normal level. I put a rag over the cap and removed it and there was a lot of pressure in there. I never measured it, but it seemed more than I'd expect. I filled the overflow tank to the split line, replaced the cap and drove it and it seemed ok for 2 days. Then the level was down again. We had a cool morning and I needed the defroster but there was no heat. Because the pressure remained in the coolant tank overnight I convinced myself that it couldn't be the head gasket. There was no evidence of oil in the coolant but it was dirty and needed to be flushed and refilled. After reading posts I bought a Block Tester Combustion Leak Test Kit from that "huge" online store that starts with an "A" and sure enough, it indicated the presence of exhaust gas in there. Since I replaced the head gaskets it's been running great. While I was working on it I replaced all the plugs, plug wires, serpentine belt, belt tensioner pulley, all the radiator hoses, and a broken MAP sensor. It's actually pretty amazing that parts aren't that expensive. I finished the job with a coolant flush and refill and an oil and filter change.

 

[melsg5]

Thanks for the info. I did buy a Lisle 75500 Combustion Leak Detector with fluid but I did not have a vacuum. It says you can use the engine vacuum but I do not see one. I tried a turkey baster as suggested elsewhere online and the color did not change of the fluid. But I am not sure how accurate this test is doing it this way.

I guess the next step is to buy a combustion tester and perform on each cylinder.

Do you mean a compression tester? They can be rented.

 

[mpk]

I brought one and it says take out all the spark plugs. Front ones no problem but the back seems hard to get to and they want the engine warm before I start. Already burned my hand will need to buy some heavy duty gloves.

In the meantime I tested the new cap to be sure, it was not a factor with the overheating the other day (actually overheated faster with the new cap the other day). With the tester it held the pressure and releases if above 18 psi as it should. I really thought I did a good job bleeding the air out the other day.

Anyway tried bleeding the air out again today just to be sure. Tried for a long time and this time, unlike the other day, after a long while it overflowed out of my spill proof funnel spilling anti-freeze everywhere. Not sure if that is a bad sign or whether I did not bleed it enough the other day.

The overflow tank was regular bubbles at first then a raging boil. Constantly bubbling and then just all foamy suds like allot of air. Then overflowed out of the spill proof funnel. It went back down and regular bubbles again. When I rev the engine the overflow tank is full by foamy like (lots of tiny bubbles) during the bleed.

 

[melsg5]

Im pretty sure shops dont heat up an engine before a compression test. The purpose is to find one or more cylinders that show a significantly lower reading.
There are other chemical tests that do not require a vacuum source, they use a rubber squeeze bulb.