# Rust in radiator but no apparent leak **URL:** \ **Category:** Maintenance/Repairs\ **Created:** [February 18, 2015, 7:10am UTC](https://community.cartalk.com/t/rust-in-radiator-but-no-apparent-leak/89075 "2015-02-18T07:10:39Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![havenoclue](https://avatars.discourse-cdn.com/v4/letter/h/ecc23a/32.png) [@havenoclue](https://community.cartalk.com/u/havenoclue)\ **Post date:** [February 18, 2015, 7:10am UTC](https://community.cartalk.com/t/rust-in-radiator-but-no-apparent-leak/89075/1 "2015-02-18T07:10:39Z")
I have coolant disappearing but no signs of a leak anywhere. Oil is fine. Car does not run hot. There is rust in the radiator though. Heater core is not leaking. I have a 2001 Pontiac Gran Prix GT. There was a recall on the cooling system but was not serviced (I didn’t own car then). A pressure test was done and it holds pressure. Help! Should I change radiator and thermostat? What else should I have checked? ---
**Author:** ![auto-owner](https://avatars.discourse-cdn.com/v4/letter/a/50afbb/32.png) [@auto-owner](https://community.cartalk.com/u/auto-owner)\ **Post date:** [February 18, 2015, 7:20am UTC](https://community.cartalk.com/t/rust-in-radiator-but-no-apparent-leak/89075/2 "2015-02-18T07:20:34Z")
You might have a pro look at the spark plugs. ---
**Author:** ![BustedKnuckles](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/bustedknuckles/32/25_2.png) [@BustedKnuckles](https://community.cartalk.com/u/BustedKnuckles)\ **Post date:** [February 18, 2015, 7:21am UTC](https://community.cartalk.com/t/rust-in-radiator-but-no-apparent-leak/89075/3 "2015-02-18T07:21:20Z")
A bad radiator cap can let too much coolant out. Also, a bad hose between the radiator and reservoir can let coolant out, but suck air back in. ---
**Author:** ![George\_San\_Jose1](https://avatars.discourse-cdn.com/v4/letter/g/e5b9ba/32.png) [@George\_San\_Jose1](https://community.cartalk.com/u/George_San_Jose1)\ **Post date:** [February 18, 2015, 7:23am UTC](https://community.cartalk.com/t/rust-in-radiator-but-no-apparent-leak/89075/4 "2015-02-18T07:23:00Z")
Couple of ideas. Check for signs of oil in the coolant or coolant the oil. What about the automatic transmission fluid? Does it look like it should, and the correct level, not over-filled? Any signs of bubbles appearing in the coolant at the top of the radiator when the engine is idling, either cold or warm? If none of that pans out probably the next thing I’d do is secure one of those UV dye kits and see if I could figure out if there’s a leak anywhere that is maybe evaporating when it hits something hot. ---
**Author:** ![havenoclue](https://avatars.discourse-cdn.com/v4/letter/h/ecc23a/32.png) [@havenoclue](https://community.cartalk.com/u/havenoclue)\ **Post date:** [February 18, 2015, 7:24am UTC](https://community.cartalk.com/t/rust-in-radiator-but-no-apparent-leak/89075/5 "2015-02-18T07:24:27Z")
There is rust in the radiator so should I change it? ---
**Author:** ![havenoclue](https://avatars.discourse-cdn.com/v4/letter/h/ecc23a/32.png) [@havenoclue](https://community.cartalk.com/u/havenoclue)\ **Post date:** [February 18, 2015, 7:28am UTC](https://community.cartalk.com/t/rust-in-radiator-but-no-apparent-leak/89075/6 "2015-02-18T07:28:14Z")
Haven’t checked transmission fluid. What does that have to do with coolant? ---
**Author:** ![Tester](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/tester/32/15976_2.png) [@Tester](https://community.cartalk.com/u/Tester)\ **Post date:** [February 18, 2015, 7:34am UTC](https://community.cartalk.com/t/rust-in-radiator-but-no-apparent-leak/89075/7 "2015-02-18T07:34:30Z")
If the vehicle has the original Dexcool coolant in the cooling system, have the cooling system flushed with universal/global coolant. Then cross your fingers. Tester ---
**Author:** ![auto-owner](https://avatars.discourse-cdn.com/v4/letter/a/50afbb/32.png) [@auto-owner](https://community.cartalk.com/u/auto-owner)\ **Post date:** [February 18, 2015, 7:38am UTC](https://community.cartalk.com/t/rust-in-radiator-but-no-apparent-leak/89075/8 "2015-02-18T07:38:29Z")
havenoclue _There is rust in the radiator so should I change it?_ **I’d probably hold off till it’s known what’s going on.** _Haven’t checked transmission fluid. What does that have to do with coolant?_ **Hope for no connection, but trans fluid is cooled by engine coolant, and once in a while something leaks and they mix.** ---
**Author:** ![oldtimer-11](https://avatars.discourse-cdn.com/v4/letter/o/e79b87/32.png) [@oldtimer-11](https://community.cartalk.com/u/oldtimer-11)\ **Post date:** [February 18, 2015, 7:47am UTC](https://community.cartalk.com/t/rust-in-radiator-but-no-apparent-leak/89075/9 "2015-02-18T07:47:45Z")
There are lines going from the transmission into the radiator with a hollow transmission cooer inside the radiator. It is called a transmossion cooler but its job is to keep the transmission fluid from getting too hot or too cold. If it gets a hole in it it lets thr transmission fluid and coolant mix. If this happens your transmission fluid will look like a milkshake. ---
**Author:** ![havenoclue](https://avatars.discourse-cdn.com/v4/letter/h/ecc23a/32.png) [@havenoclue](https://community.cartalk.com/u/havenoclue)\ **Post date:** [February 18, 2015, 7:49am UTC](https://community.cartalk.com/t/rust-in-radiator-but-no-apparent-leak/89075/10 "2015-02-18T07:49:19Z")
There is new coolant in the radiator (as I have to keep adding). I have Prestone Dex-cool in the radiator as that’s what my car calls for. ---
**Author:** ![havenoclue](https://avatars.discourse-cdn.com/v4/letter/h/ecc23a/32.png) [@havenoclue](https://community.cartalk.com/u/havenoclue)\ **Post date:** [February 18, 2015, 7:51am UTC](https://community.cartalk.com/t/rust-in-radiator-but-no-apparent-leak/89075/11 "2015-02-18T07:51:56Z")
Ok I will have that checked ---
**Author:** ![havenoclue](https://avatars.discourse-cdn.com/v4/letter/h/ecc23a/32.png) [@havenoclue](https://community.cartalk.com/u/havenoclue)\ **Post date:** [February 18, 2015, 8:07am UTC](https://community.cartalk.com/t/rust-in-radiator-but-no-apparent-leak/89075/12 "2015-02-18T08:07:22Z")
And according to the recall they change 3 throttle body fasteners and put sealant but they won’t because the recall is closed. ---
**Author:** ![edb1961](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/edb1961/32/122_2.png) [@edb1961](https://community.cartalk.com/u/edb1961)\ **Post date:** [February 18, 2015, 8:47am UTC](https://community.cartalk.com/t/rust-in-radiator-but-no-apparent-leak/89075/13 "2015-02-18T08:47:40Z")
Have it checked for a intake manifold gasket leak if it’s a V6. I believe this year Pontiac was part of the Dexcool Class Action settlement. See [http://www.aboutlawsuits.com/gm-recalls-buick-chevrolet-oldsmobile-pontiac-3520/](http://www.aboutlawsuits.com/gm-recalls-buick-chevrolet-oldsmobile-pontiac-3520/) for a list of vehicles included in the suit. As far as I know the suit is closed and no more claims can be made. My 2000 Blazer developed an intake gasket leak a few months after I bought it in 2003. The only symptoms were a slow loss of coolant (~1 pint/month) and an occasional whiff of antifreeze smell. Have the oil checked for the presence of coolant. My mechanic saw a couple of drops of coolant as the last of oil drained out of the pan during an oil change. Coolant in oil is very bad as it will displace the oil from the main bearings. Ed B. ---
**Author:** ![havenoclue](https://avatars.discourse-cdn.com/v4/letter/h/ecc23a/32.png) [@havenoclue](https://community.cartalk.com/u/havenoclue)\ **Post date:** [February 18, 2015, 7:47pm UTC](https://community.cartalk.com/t/rust-in-radiator-but-no-apparent-leak/89075/14 "2015-02-18T19:47:32Z")
That’s how my car is. I don’t have to add much when I do have to add and very seldom do I get a quick whiff of antifreeze. But only for a split second. ---
**Author:** ![havenoclue](https://avatars.discourse-cdn.com/v4/letter/h/ecc23a/32.png) [@havenoclue](https://community.cartalk.com/u/havenoclue)\ **Post date:** [February 18, 2015, 7:50pm UTC](https://community.cartalk.com/t/rust-in-radiator-but-no-apparent-leak/89075/15 "2015-02-18T19:50:53Z")
I have this recall on the oil leak causing engine fire fixed. I got the notice for this and brought it in. ---
**Author:** ![circuitsmith](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/circuitsmith/32/40376_2.png) [@circuitsmith](https://community.cartalk.com/u/circuitsmith)\ **Post date:** [February 18, 2015, 8:51pm UTC](https://community.cartalk.com/t/rust-in-radiator-but-no-apparent-leak/89075/16 "2015-02-18T20:51:21Z")
Even though GM calls for Dexcool in this engine you’re better off with something else. There have been problems with Dexcool, especially in systems with a small leak, which exposes the coolant to air. ---
**Author:** ![dagosa](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/dagosa/32/9837_2.png) [@dagosa](https://community.cartalk.com/u/dagosa)\ **Post date:** [February 18, 2015, 10:01pm UTC](https://community.cartalk.com/t/rust-in-radiator-but-no-apparent-leak/89075/17 "2015-02-18T22:01:31Z")
It definitely needs a pressure test and a complete look see. Rust through in the radiator fins may be hard to see as well as coolant leaks otherwise. ---
**Author:** ![keith](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/keith/32/5518_2.png) [@keith](https://community.cartalk.com/u/keith)\ **Post date:** [February 18, 2015, 10:57pm UTC](https://community.cartalk.com/t/rust-in-radiator-but-no-apparent-leak/89075/18 "2015-02-18T22:57:03Z")
The rust may not be rust. I can’t see it from here so I can’t say for sure, but Dexcool turns a rusty brown when the corrosion inhibitors are depleted. That is a sign of serious neglect, having gone too long between coolant changes. When coolant this old is drained, it does leave a brownish coating on the insides of the radiator fins, but it is usually not thick enough to do any damage or clog the radiator. Dexcool will last at least 5 years, but I have seen systems where it was in for 7 years and still good, a little cloudy but good, and I once bought a 92 Chevy Van that was converted for handicap use that had no record of the coolant ever being changed, and it was like draining mud. I don’t have a problem using Dexcool, in fact I used it for the first coolant changes in my 97 Honda and 97 Nissan PU. The Nissan had a chronic leak from new, about a cup a month that I had not been able to find until I put in the Dexcool. The bright color of the Dexcool showed me the leak in short order, a small casting defect in the thermostat housing. But with the wide availability of the Universal Long Life coolants that work just as good, this is what I use now in all may vehicles. ---
**Author:** ![havenoclue](https://avatars.discourse-cdn.com/v4/letter/h/ecc23a/32.png) [@havenoclue](https://community.cartalk.com/u/havenoclue)\ **Post date:** [February 20, 2015, 8:21pm UTC](https://community.cartalk.com/t/rust-in-radiator-but-no-apparent-leak/89075/19 "2015-02-20T20:21:01Z")
Bottom of radiator was full of sludge and thermostat was stock half open. Had them changed and cooling system runs perfect now. Now the only issue I have is abs light is on and don’t know why. Lines seem to be Ok. And input turbine sapped sensor is reason for service engine light. Which both lights go off and then after a few minutes come back on when a put car in gear and let foot off brake a little for car to start rolling. ---
**Author:** ![havenoclue](https://avatars.discourse-cdn.com/v4/letter/h/ecc23a/32.png) [@havenoclue](https://community.cartalk.com/u/havenoclue)\ **Post date:** [February 20, 2015, 8:23pm UTC](https://community.cartalk.com/t/rust-in-radiator-but-no-apparent-leak/89075/20 "2015-02-20T20:23:11Z")
There was no leaks when radiator was pulled out that were found. Coolant was not able to pass out radiator on bottom like it should have been able to due to sludge. Pressure test was done and it holds pressure. [Next page](https://community.cartalk.com/t/rust-in-radiator-but-no-apparent-leak/89075.md?page=2)