Question/Help 3.0 V6 Cooling System Issue

[Joeg]

Hey Guys, I have a strange one although I think the answer is a head/head gasket issue. The cooling system is getting pressurized and will blow the cap off the overflow tank. It happens intermittently maybe 4 times in the last month. I replaced the T-Stat, flushed and filled the coolant and went as far as adding the dreaded head gasket sealer. That was 2 weeks ago and it ran fine until yesterday. A few observations that may help.
1. dropped the oil it looked fine.
2. coolant (dexcool) did not look great - muddy looking
3. it will run cold won't move- then it will spike to Hot for a seconds and then down to normal. This usually means it has blown the overflow cap. It may sound strange but I have noticed if it's running cold, I can hammer the brakes a few times and the needle will rise and go right to normal and stay there.
4. drove 100 miles yesterday and it ran fine normal temp the entire time but did push maybe a quart of coolant into the overflow.
My buddies are telling me head gasket but before I go down that road thought I would check with the experts on line for opinions. Thanks guys,

 

[Big Jim M]

If you drove it a hunnert miles and it was fine.. It DEFINATELY ain't a head gasket.
First thing to do is open the radiator and make sure it is FULL. Not just the overflow tank.
I would suspect either the radiator cap or the fan clutch from your post.
You say it blows the cap off of the overflow tank..
Does it lose it's coolant when it does this?
Does the temp gauge show it is in the red and the overflow tank is steaming?
If there is a small coolant leak somewhere the engine could be a bit low on coolant and the air which displaced the coolant allows parts of the head to get waaaay too hot.. Which in turn will boil the coolant. Small leaks are very hazzardous.
Big JIm

 

[Joeg]

Jim, It has lost coolant but over the course of a few days I can see the level in the overflow rising then if she blows the top it will spill out... I have been removing the excess and putting it back into the radiator which I have been keeping full. You can hear it bubbling even on times when it does not blow the cover. Just drove 5 miles at lunch and it was pushing coolant into the overflow, and I pulled the overflow cover and there was pressure there. I have notice a few drops of coolant on the garage floor recently, but for the life of me I can see where the hell it is coming from. Also, I have only seen it spike to hot just for a second or two then back to normal.

 

[TomB1269]

If you do suspect a head gasket, then do a compression test on each cylinder and check each plug in the process. I am willing to bet that it spikes hotter when you give it extra gas for an extended period (moderate to long hill climb, long pass on the highway), basically where you bring the RPMS up to an hold at or above 3200 / 3500 rpm. This is a sign of an air pocket. If you notice the center of the outbound (to rad) hose is actually the higher than any other part of the coolant system (where it goe over the alternator).
This will create an air pocket when you do any coolant system work. In order to get the air out you have to let the engine come to full temp (good flow thru outbound hose) and fully open the T-stat with the cap off the radiator.

 

[Joeg]

Tom, I don't think that is the case it seems to happen more frequently on short drives or first time it warms up in the morning. When it does spike hot it blasts up for maybe 1 or 2 seconds then right down to normal. It's a strange one for sure. Have tried the air pocket remedy but will give it a shot again along with a new Rad Cap.

 

[JP02XLT]

Water pump not circulating? I have seen the pump fins rusted away & the WP does not move the water fast enough.

JP02XLT

 

[Big Jim M]

Joe what I THINK you are missing is the fact that the coolant tank is SUPPOSED to have coolant going into it as the engine and coolant gets hot..Heat expands the coolant..then as the engine cools the CAP allows the vacuume to pull coolant FROM the tank back into the engine.

The small hose between the radiator and the tank MUST be tight fitting and have NO CRACKS in it.

I'm betting when you do find the small leak your problems will be taken care of. Get a flashlight and lay yourself UNDER the vehicle and FIND THE LEAK.. It is within a 3 foot area..surely you can find it.

That hunnert mile drive told us the head gasket and heads are Ok.

Big JIm

 

[Joeg]

Jim, Appreciate the advise and I hope your correct on the Head Gasket. If I had to venture a guess it looks to me like there is fluid coming from the very top left corner of the water pump (pass side), running down the block onto the transmission lines. Any idea why hammering on the brakes a few times would seem to make the condition clear and the temp go to normal, or is that just my imagination.

 

[Big Jim M]

Nope! No idea.
Big Jim

 

[jwranger96]

mine with a small crack inbetween the valves on cylinder 5 did kind of the same thing and until i had a trailer with 3 4wheelers on it did the temp gauge spike all the way up going up the mountain but when i backed off of it came back down... pull the plugs and see if its burning any water, you will know by the plugs... never did my oil look any different than new, but my coolant looked like rust water out of nowhere

 

[Runnin'OnEmpty]

Joe, are you sure the thermostat is pointed in
the correct direction; with the pill end toward the
block, and the pointed end toward the radiator?

 

[Joeg]

Runnin, Yea I got er in correctly. Replaced the Radiator Cap last night and the overflow hose. I assume I should get a pressure test first thing, then a compression check but will that certainly indentify the issue. A local shop blew me off when I called for the pressure / compression test. I can pull the plugs this weekend although that looks like a PITA. Could a water pump cause this type of problem?

 

[Big Jim M]

neither of those tests will tell you anything... FIND the leak and repair IT! Then see what happens..
Big JIm

 

[kukaepe]

I'm new to this site and have been doing some fishing around. You might look at this site, I found it fascinating that this guy's 3.0 would run at all with a water pump in this condition. See http://blizzard.zmm.com/waterpump/ If you have never replaced your water pump, perhaps it would be worthwhile if this is a common issue even if it doesn't resolve your problem. Just a thought...

 

[betomonroy]

You may also be looking at a very clugged up radiator. Flushing it will NOT be enough. Trust me.I suggest You Remove and Replace Water Pump since you mentioned a leak that seems to be occurring from there. But also have the radiator tanks removed by an expert to clean the lines one by one. Or buy a new one since this operation may be as expensive as getting as new radiator.