Losing coolant

[chessy56]

OK- this thread is getting a bit long in the tooth, so hopefully it'll be on to better things soon.

Started by releasing the reservoir cap- "slight" amount of pressure release with the engine cold. Ran about 45 minutes averaging somewhere around 50-55 mph- stopped to check upper hose at filling station- warm, but relatively soft (little to no pressure). Ran the balance of the 250 mile run @ 60 (+/-) mph and checked the hose pressure after getting off of the freeway- warm and it had some pressure, but not "hard" like I was accustomed to in the past. Checked the upper hose after an overnight sit (cold engine)- soft, no stiff hose pressure as I had in the past. Released the reservoir cap: no pressure released at all. Noted that the coolant was a bit lower than when I started- maybe an air pocket finally moved out (no signs of coolant overflow however). This was running in 40 deg F air temp with a wind shield over the front grille. The Edge monitor I use reported coolant temps as high as 192 and as low as 183; averaged 186-188 across the trip.

I noted on the repair's bill of materials that both thermostats and the reservoir cap had been replaced in addition to the head gaskets ('stats' were replaced with an earlier tear down before). If this "zero pressure" state should be normal, I'd question if there was a redesign of the cap or if the original cap was partially at fault all along (I did notice that the new cap has no gasket- appears to be plastic on plastic seal; can't remember what the original cap looked like). Since 2001, the dealership replaced the injectors twice, I did the job myself once. The head gaskets were replaced once before and a coolant seal on the backside of the engine block required replacement last year as well. All of this work required a drain/re-fill of the coolant and in every case, I always had sufficient pressure to result in the upper rad hose being "very stiff"- regardless of whether the engine was hot or cold. And no lost coolant due to an over pressure condition! I'm baffled.

I spoke with my service writer- he'll talk with the repair tech next week. We'll let you know. Thanks to all for responding.
Gary

[rapidoxidationman]

Water under the bridge and all that, but it sounds like the first head gasket job was botched. It took a long time for it to degrade to the point that you needed to have it done again (properly this time, hopefully), but here's some anecdotal evidence for ya:

I bought my '05 used about 6 years ago. When I got it, every now and then I could get a slight scent of coolant. Had to add a cup or a quart every month or so. Drove it across the country, no problem. Eventually, it got to the point where the cooling system was belching fluid and I was adding a gallon a week. Hard hoses when it was warm, pressurized hoses when it was cold. That's when I took action and replaced the head gaskets, solving the problem.

Sounds like you've got the problem licked!

[DmaxMaverick]

The coolant pressure cap should have an O-ring, not a traditional gasket. It's located on the center part, just about mid-way, and under the threaded outer part. It also causes the friction you feel when installing/removing it. If it doesn't have this, or you don't feel the friction of the seal engaging the reservoir neck, it won't hold pressure at all, and may explain a few things.

[SoTxPollock]

My top radiator hose seems to be collapsing due to vacuum when coolant is cold, what does that suggest?

[DmaxMaverick]

My top radiator hose seems to be collapsing due to vacuum when coolant is cold, what does that suggest?

Time for a new pressure cap, and probably, new upper and lower hoses. Also check the turbo coolant connector hose behind/above the fan pulley, which is also likely in need of replacement (it's ~3" long). These are wear items, and with your time and mileage, are due.