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Discussion Starter #1
Taking my cooling system issue a little farther...thanks to others for replies on previous post regarding the temp sensor location.

What I have is a once-in-a-while leak, apparently only when climbing a hill just after I've added water to the radiator or overflow tank. I've not been able to locate the source of the leak, probably because it is on the condenser side of the radiator and out of view.

Or not. Here's what I observed:

Starting with a full radiator and the coolant overflow tank between max and min, and with a new radiator cap tightly closed, under ordinary conditions, the temp gauge stays resolutely at the exact midpoint on the gauge, even when climbing a hill. The most recent test of that, about 6 miles or so up a sustained gradual hill at 50+ mph, confirmed it. It showed NO leak.

I went back down the hill, put a piece of cardboard between the radiator and condenser to see if the temp gauge would climb above the middle (to confirm it is operational) and started back up. The gauge did begin to climb after a few miles on the hill, though never reached the red. When I found a place to pull over to check, there was water dripping steadily (but less than a steady stream) from near the extreme front passenger side, forward of the lower hose and overflow tank outlet. Couldn't see anything though, had no flashlight (my mistake).

Then I removed the cardboard, went home and kept the engine running for 15 more minutes and never saw a leak again.

Once the engine cooled, I discovered that the radiator was still completely full right up to the filler neck, BUT...the reservoir was now below the min mark by an inch or two. That suggests to me that the leak was water leaving from the reservoir, but I can't explain exactly why it would drain below the min mark. Or is this proper functioning of the system? I think I can accept that coolant is leaking from the radiator and being sucked back in from the reservoir. I think that makes sense.

Each time I've noticed the leak, it's been right after I've added water to the rad and reservoir.

I have been told that it takes some time for the system to "stabilize", ie, that there may be too much or too little water in the system and sometimes it gets spilled out or needs to be replenished until it's where it really needs to be.

I'm inclined to replace the radiator regardless, it's probably the original one and the car is just over 150k, so it's probably due. And it would be a lot cheaper to do it myself as a preventative measure, than to have a problem far from home where I need to pay someone else. But if the radiator isn't the problem, I don't want to be distracted from the real problem....like a head gasket issue. I have previously checked the radiator for combustion gases and that seemed to be negative, and the engine runs great with excellent CA emission test very recently. I didn't see any signs of a problem with the water pump, though I think I'll replace that too just to be sure.

I'd do a compression test but it's such a difficult process to reach the rear bank of plugs that I hesitate to dive into that, would probably have to hire someone for that job.

Anyone have any insight on this? I'll be grateful for suggestions.

BTW, this is a 3.3 L engine. 152k, I've put only 1k on it in the six months I've owned it.
 

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With no visible leak from the radiator or no wetness on the radiator sides or bottom, I'd be reluctant to just replace the radiator.
To me, this sounds like it could be a radiator hose or a heater hose with a slight crack in the rubber. These sometimes occur right where the hose clamps to a fixed opening. A little flexing of hose over the years can create these tiny cracks and the heat and pressure of hot coolant can push a few drops out that would be difficult to spot. Are these all the original hoses? Are there any spiral clamps that need to be snugged?

Also, your vehicle may have the plastic restrictor in the heater hose (up near the brake booster). Both myself and Ray (another poster on this board) had that plastic restrictor leak and we both took it out of the system (replaced with straight heater hose) with no ill effects.

Honestly, I think you will need to get a hold of a cooling system pressure tester to pressurize the cooling system to 15 PSI so that you can take your time and look for tiny drops or a fine mist of spray. Otherwise you may be chasing this problem for a long time.

To some degree, the coolant will expand and contract from hot to cool, so rising and falling levels in the reservoir are normal with temperature changes. If I had to guess, some of the fluid may have been expelled when you got near hot, but you probably lost a little from another obscure leak, as well.

Check with your nearest auto parts store or auto repair facility to see if they can lend you a pressure tester adapter.

I see a used one on E-Bay at: http://www.ebay.com/...4b26bc0&vxp=mtr
 

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Discussion Starter #4
Thanks once again John. You reinforced my hunches.

I'm nearly certain the radiator hoses (and probably heater hoses too) are original, so they are immediately suspect - the clamps look like factory squeeze type rather than the familiar screw type. I bought new radiator hoses along with coolant just after I bought the car in April, but was hesitating until I could figure out how to change the heater hoses, they seem buried somewhere in the congested engine bay, I can't even see them. I didn't want to waste good coolant until I could deal with those heater hoses, but this "leak" has forced my hand.

I was looking last night for prices on pressure testers, and also found another forum where a few posts pointed out that it was hard to get a perfect seal at the radiator. I will probably see if I can borrow a tester. The store I use (Napa) doesn't, and I feel awkward borrowing from Autozone when I'm not really a customer there.

If I have no luck getting a tester, then I think what I'll do is change the rad hoses and repeat my tests, and if that solves the problem, I'll take this to a shop to replace the heater hoses. Thanks very much for your advice. On the other hand, most of my use of this car will be long trips, so prevention is a high priority for me, and I may just replace the whole works for peace of mind. I got the car cheap enough to justify that option.
 

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I'm sure the engine also has steel freeze plugs. Once or twice in my life I have come across one that seeps or had rusted enough to cause a leak. It would be prudent to check the block for seeping plugs. With today's compact engine compartments, that is easier said than done.
 

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Coolant leaks can be intermittent and misleading as to their source. Fluid will usually blow back (road draft) and down (gravity). Dried coolant can leave behind whitish streaks on a dark surface. You may also see a whitish dried coolant trail from the water pump weep hole.
I have seen crusty deposits between the aluminum timing cover and iron block if you look up from underneath. Greenish-white crystal fuzz for the green coolant and orange-white crystal fuzz for the orange coolant.
There are rubber o-ring seals between the t/cover and block that leak. The aluminum cover also corrodes from coolant deterioration after a few years. It is like an electrolytic action that takes place between dissimilar metals. This corrosion can be cleaned up when replacing the seals.
 

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If you have the rear / heater AC option on that mini-van, there is a pipe manifold attached to the firewall that splits coolant flow between the front and rear. You have to remove the wiper cowl and intake runner plenum to gain sufficient access. There are 4 hoses attached to the manifold and 8 hose clamps.

There is a heater hose that connects the thermostat housing to the water pump. The top end of the hose clamp can be reached from above. The lower clamp on the water pump is difficult. You need to remove the lower pulley splash shield and oil filter (3.3 V6) to get moderate access. There is a moderate length, intermediate pipe that connects the heater return collector (from the manifold) to a pipe that runs between the engine block and radiator. Close to the water pump there is a hose to connect the intermediate pipe to the water pump.

There are 2 hoses underneath the vehicle and behind the front suspension cross members. There are 2 hoses in front of the right rear wheel and there are 2 hoses underneath the right rear wheel interior trim cover / panel. You have to remove the rear seats, remove the panel to gain access to the hoses that connect piping to the heater core.

If you take it to a shop you will get charged a lot of hours of labor. It is not difficult but time has to be spent removing stuff to gain access. If you want to save money and have 4 - 6 hours you can do it yourself. All heater hose is 5/8 inch diameter. With the rear heat / AC option there are 12 separate lengths of heater hose around the engine, underneath the vehicle and inside the right rear trim panel.
 

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Pull the body panel (4 screws I think) so you can see the right end tank on the radiator where the top radiator hose connects. That's where my radiator cracked and the location and characteristics of your problem sound hauntingly familiar!
 

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Check your hose clamps, Ray. If you have a loose one, believe me, it can drive you nuts!
 

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Check your hose clamps, Ray. If you have a loose one, believe me, it can drive you nuts!
Not me this time Chuzz :unsure: Got all my leaks fixed for now.
 
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I had thermostat gasket leakage spilling right on ex manifold so smelled it and lost fluid, but just confused me.. cause it didn't leak till it went to temp so then it vanished bc the mani was also hot enough to vaporize the fluid!
 

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Thanks all. I borrowed the tester from Autozone and isolated the problem in a minute. The system just would not hold pressure, needle crept down slowly and steadily. I never saw the actual source of the leak because my view was obstructed, but the bottom of the radiator on passenger side was wet and dripping, and the hoses and water pump were all fine. So the radiator is on order from Advance Auto.

For what it's worth, I benefitted from speaking directly to a sales person at Advance Auto. I asked about the promo code and he explained that it was good for a coupon for future purchase, which wasn't much value to me. He mentioned that he could get me a different code with different benefit, so I ended up with 20% discount on that purchase. Lesson here is to ask for what the promo does, and if that's not what you want, ask for options.
 

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Well, your first hunch was right but I'm glad you were able to get your hands on a tester and confirm that it really was the radiator.
 

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Well, your first hunch was right but I'm glad you were able to get your hands on a tester and confirm that it really was the radiator.
I had a feeling ..... based on my recent experience!
 
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