I am working on a 2005 Uplander with 3.5 engine. It is loosing coolant slowly, but I cannot find where. There are tiny bubbles that appear at radiator cap opening. The bubbles do not seem to change with RPM.
Question:
- what are some common places to look for a leak?
- what all could cause the tiny bubbles? They are slow, but steady.

Thanks to all who reply.

 

Have a mechanic pressure test the system.

 

'05 Venture shouldn't be much different here. Bleeder vavle (brass screw in a plastic pipe). Top of the motor, passenger side and toward the front. Look at part #7.

How many miles? Overheating? Any other issues?

If you can't find it...+1 to Papa Bear's idea.

 

I pressure checked the system and saw wetness in the back corner (near firewall) where the timing cover and oil pan meet. I also saw some near back corner of head where it meets the block. I had a garage check it today they think it is the timing cover gaskets.
$910 for the parts and labor. I am going to get a second opinion.

 

I degreased the engine and pressure checked. The picture below shows same leak areas, but with the tester removed, radiator cap back on and engine running. The coolant was visibly seeping where head met block but in pic it looks dry due to engine heat.




2005 uplander - 3.5 (coolant leak)

 

the coolant cross over pipe gaskets are leaking. timing covers do not leak coolant.
4hr job at a shop.

 

Have you added some Bars Leaks to the radiator?

I would start with that.

 

fix it right, I would never recommend adding any "stop leak" its only a temporary fix at best and likely to cause other problems laterl