Symptoms on my wif'e's 2007 Uplander LT 3.9L with 85K miles:
- Coolant was changed 4 years ago @ 47K miles (Prestone Dexcool 50/50 mix), I always maintain my vehicles per maintenance schedule
- Hence, current coolant is 4 years old with less than 40K miles on it
- While wife was driving home, temp gauge went to 3/4 mark (normally always at 1/2 mark), she called me and I told her to pull over and shut it off
- I arrived, saw no external signs of coolant leak, but was able to add around 3/8 to 1/2 gallon of DexCool 50/50 mix and the overflow was empty
- Drove it home (about 15 mins of stopping & going), temp gauge never left the 1/2 mark, but I also left the AC off
- Oil does not appear to have coolant in it (no white residue anywhere), exhaust is normal with no liquid drips or white smoke, engine idles, accelerates and runs smooth and normally
- Laying on the ground by the right front tire and reaching my arm up behind the belt driven accessories, I saw faint suggestions of a liquid, washed hands then wiped them all over those items, smell = coolant, appears to be small & slow leak in that area

Question 1: While all the above seem to suggest the coolant crossover pipe, I want to confirm where this pipe and its gaskets are located. Anyone have pics or service manual graphics?

Question 2: I also stuck a funnel in the filler cap hole, added coolant mix, started and had the wife gradually accelerate fo around 1600 rpms. Saw small bubbles in the funnel, especially under acceleration. Heard this indicates an internal leak (i.e. head gasket). Drove the vehicle briefly to also perform the "heater" test where, with the heat on, cool air comes out at idle and low speeds and hot air only comes out at around 40+ mph. Hot air came out the entire time. Are bubbles in a funnel filled with coolant a sure sign of an internal leak (head gasket / warped head ) or not?

Thanks!

 

#2 the low heat at idle is a indication of air pockets/low coolant in the cooling system


the crossover gaskets leak down the rear passenger side of the motor. waterpumps leak further forward


if you think you have a head gasket problem; do a compression check.


3hrs is the time to change the xover gaskets.
you will have to relocate the fuse box, remove the alternator, reservoir, anchor brace, belt, tensioner, idler pulleys, coolant hoses, coolant pipe and crossover housing. then you will need to find out which design crossover you have...1st or 2nd. usually the old gaskets will have torn sections.

 

Thanks tech2, I was thinking about doing a compression test, but how the heck to you get to the rear bank (cylinders 1, 3, 5)?

 

There are good Youtube vids showing how to change spark plugs in an Uplander.
You have to rock the engine forward.
It would be a great time to replace the spark plugs while you're at it.

My 2007 Uplander's crossover gasket(s) were changed under warranty.

Good luck.

 

Thanks Papa Bear. How recently were your Uplander crossover gaskets changed under warranty?

 

Early 2010

 

would a crossover gasket problem ever lead to oil in the coolant?
generally speaking, how significant are the leaks from a crossover gasket? i definitely do not see drops/puddles on the ground, i dont believe i have ever noticed seeping either but i cant recall inspecting that general area extremely close either... thanks

 

nosiree

 

thx. my 'oil in coolant' problem may be a 'transmission fluid in coolant' problem... i dunno how to distinguish one from the other..
radiator is new ac delco... maybe 6-7k miles on it. thinking of bypassing the oem tranny cooler completely now... will give me a better idea at least...

 

smear the oil on bright white paper or towel. Transmission fluid is reddish.