I smell coolant

[donky4444]

I keep getting a light smell of coolant in my car when it is running. I have checked all over in the engine bay and can't find a leak anywhere. I have also checked the oil cap to see if the oil is looking white or leaving a white film on the cap to see if coolant is getting in there but that looks good. I have also checked all under the dash to see if it's coming from the heater core but nothing. I don't smell it coming from the vents and it gets stronger when the car is sitting still and goes away when I am moving down the road. Any suggestions??

[ChilinMichael]

Sure, got a suggestion. To make sure you aren't imagining things let's start with the basics, now..of course a small (and I mean small) leak can cause a smell, eventually...you'll be losing coolant if it's leaking (This is fact)

So, I don't know how GXP's are but, if you have an overflow tank where you can see the level, mark it cold (now make sure of the outside temps because, if the outside temp varies enough even when the car is cold, the level of the overflow tank can too, so try and do this on similar temperature days)...then check it a few days later and keep checking. If you notice you are leaking a decent amount..then well...you aren't insane and it's time to start really checking.

As far as where it's coming from, obviously your ventilation system sucks in air infront of the windshield...if it's the heater core a very small amount even would make a good smell, I've seen them smell before they even really start leaking hard...just enough to burn off and cause smell but not puddle up....if it's something from the engine bay, assumption (if be correct) would be that it would have to be a much larger leak to get the smell into the cabin compared to a smaller heater core leak...


*edit in*Also, have you had a coolant change done recently or pour some coolant into your system?

[donky4444]

Thank you for the advice. I have not done anything to the coolant system since I bought it 2.5 years and 53k miles ago. I have been reading the caddy forums and I now realize with this engine that a system flush should be done every 2 years due to history and dex so that is a must at this point. Hopefully this week or next I will have that done.

[ChilinMichael]

When you do that, know that the Northstar calls for (3) GM coolant tabs, if I remember right, to be installed in the lower radiator hose because gaskets in the Northstar never seal right and GM's answer was installing their version of a stop-leak tablet into the coolant system. Look it up first because I'm not 100% sure, but almost close to positive and not many know this.

[1fatcat]

Water pumps and water pump housing cross over gaskets are common.

[CMNTMXR57]

You're probably seeing the same thing I did. I could smell it when the engine was running. Problem was, I could never find the leak, because by the time I got it to my old garage, where I could get it on the lift, the car was up to operating temp and burned off what coolant seeped down over night, so there was no trace.

I finally found it though. One day I was there at the old place for a long time, had the car up on the lift for a long time while I was doing other stuff, and sure enough, it leaked. It seeped down the back of the motor from a freeze plug (as best as I could see up between the block/pan and transaxle), and leaked down onto the front exhaust cross over pipe and support plate (it runs UNDER the engine and trans on our N*).

My solution, as I've posted here before a couple times. Went to Napa. Picked up a can of "Block Seal"

1) Drained cooling system like normal
2) Flushed/drained cooling system like normal
3) Added the "Block Seal" with water to the cooling system, flushed through the engine, letting it run and flush again for about 30 minutes.
4) Drained cooling system again, let cooling system sit open (cap off, drain open), for 24 hours to allow for the "Block Seal" to cure as the system dried.
5) After 24 hours, refilled cooling system with the appropriate mix of coolant, purged, and sealed cooling system.

Since then, I have not had an issue. No more leaks, no more smell, no nothing.

[donky4444]

Today I took it in for an oil change, tranny fluid and filter change and a coolant system flush. I had the pressure test the coolant system and they said there is nothing leaking. They had it hooked up under pressure for 2 hours and no changes. Hopefully the flush and fill with the GM stop leak tablets that go in it will do the trick. Only time will tell.

[CMNTMXR57]

When it's hot (or been warmed up), the freeze plugs or any small head gasket leak, probably expands, effectively sealing it. The smell you're getting is the stuff the seaped out when it was cold, now burning off. Hopefully the "Pills" you put in will fix it. Otherwise, if you have the means available, before you start the car up when it's cold, crawl under, and see if their are any discernable water/coolant particulary on the exhaust crossover pipe and/or that heavy steel protector for it. It'll leak down the back of the block and down this part of the exhaust if said leak is present. Once you start it up and warm it up to operating temp, the exhaust burns it off, hence the smell you're sniffer is detecting...

[1fatcat]

All very true and good info. Also, just to let everyone know, the original crossover gaskets were the same plastic frame/rubber bead seal as the 3.8 lowers. The new, updated ones are aluminum frame/rubber bead seal...just like the updated 3.8 lowers.

[two bonnies]

When you do that, know that the Northstar calls for (3) GM coolant tabs, if I remember right, to be installed in the lower radiator hose because gaskets in the Northstar never seal right and GM's answer was installing their version of a stop-leak tablet into the coolant system. Look it up first because I'm not 100% sure, but almost close to positive and not many know this.

This worked like a charm for me.

I had the same problem. A slight whiff of coolant that disappeared and could not be traced. I put two tabs in after having crushed them and mixed them with Dex-cool in a small cup until dissolved (somebody here suggested that - can't remember who). Did that about 6-8 months ago. No problems since.

[Skippy1827]

As a Northstar owner, I had a faint smell also once in a while. I was topping off the coolant tank once a month. It was the crossover gasket. There was coolant pooling there, but not enough to drip. They replaced that and the plenum. almost $1000.00. Hope you solved it.

[2.3 turbocoupe]

I've had the coolant smell for about a year now. It has not gotten any worse, so I've just left it alone. I've topped off the coolant twice in the last year. It notice the smell when the car is parked after having been driven. It's more noticeable in cool weather. I thought it was probably the coolant crossover, but I've not been able to see anything from the top of the engine (and have not gotten underneath the car). Thankfully there are no bubbles in the coolant or other bad symptoms. I'll probably try some form of sealant when I can get around to it.

[CosmicVagabond]

I'm having the same problem as the OP and have considered some form of stop-leak but have heard that it will clog necessary circulation in the coolant system. Can this be used safely? If so, any safer brands/methods of use?

Thanks guys

[CMNTMXR57]

OK, again, the GM Cooling system seal tabs are SAFE to use! GM uses them in service to seal small leaks such as seepage from freeze plugs, seals, etc... Crush them up and put them into the overflow tank (as there is no access point elsewhere).



If it's something major however, nothing other than repair will fix it.

[CosmicVagabond]

Thanks for the reply. I didn't realize that it had been extensively covered.

[CMNTMXR57]

Yes. N*'s lot in life is to leak fluids.