Dexcool Picture of the Day.

[440Magnum]

Originally Posted By: onion
Much as I disdain Dexcool, I gotta differ somewhat. IMO, GM's plastic intake gaskets, plastic intake manifolds, and certain radiator caps WERE a bad design in and of themselves. I've seen those plastic gaskets fail even without the use of Dexcool (these failed routinely in '94 and '95 engines, which didn't come with dexcool). The plastic intake manifolds in the 3800 engines crack due to EGR heat. And those S10 radiator caps let air into the system regardless of what type of coolant is in the system.


OK, I'll back off on "nothing wrong" with the designs. I've seen plastic gasket frames work well on other manufacturers' engines, but then the EGR didn't run right through a plastic gasket, either. It still strikes me as hilarious that *any* manufacturer could get a radiator cap wrong after doing this for 100-odd years. Just how many different rad cap designs to there have to really be, anyway? That's one of those things where if I were designing the car, I'd go out of my way to use a very common, standard part. Just like every gasoline engine I used would take an L3001 (FL-1A equivalent) oil filter ;-) One of the reasons I've always liked Mopars is the fact that the little things (like rad caps) tend to be the same (or backward compatible) over a nearly 50-year span and hundreds of different models. But they didn't do the same with oil filters, unfortunately.

 

[JakeR22]

Coworker has an '05 Grand Am with the 3.8L, with 50k miles on it.

I took a look inside the overflow, looked like used motor oil in there. I suggested he get a coolant flush.

 

[jdeare]

I've got a 2001 3800 Buick, it had the original coolant in it until last summer. Supposedly there were no signs of sludge, but they also supposedly replaced the Dex with Peak Global, which I found out later was not true (they told me the Peak was the same color as Dex, I didn't bother to check). So now I don't really know what to think, except for thinking I need a place with a garage (current condo rules state no car repairs in the lot).

I've noticed now though, my coolant level seems to be dropping. I'm guessing a gasket leak, but I have never been able to find any evidence of it except for the dropping level in the overflow tank.

 

[sciphi]

jdeare, get a pressure test done NOW. The factory nylon lower intake manifold gaskets are known to degrade in the presence of Dex-Cool.

Not to sound alarmist, but a dropping coolant level on a late 90's to early 2000's 3800 is serious because of the design of the engine places coolant passages right alongside air passages, with only the gasket and an inch separating the two passages. Once the gasket starts to go, it's a very short trip to the cylinders, and then you have antifreeze in your oil, which is very bad news.

If it does happen to be the gaskets, have the mechanic replace the upper intake manifold as well since that needs to be taken off to replace the lower gaskets.

Search for Pontiac Bonneville forums, there are a lot of members within a 2-hour drive who likely could be persuaded to tackle this.

 

[jdeare]

It's going in for a transmission fluid change soon... I will have them do a pressure test also.

 

[Al]

Originally Posted By: jdeare
It's going in for a transmission fluid change soon... I will have them do a pressure test also.

Don't count on the pressure test showing anything unless you have the equivalent of 50+ ppm of potassium or so in a UOA. Also sometimes the leak opens up when Hot or vice versa. You need to do a UOA.

 

[onion]

Originally Posted By: jdeare
It's going in for a transmission fluid change soon... I will have them do a pressure test also.


Check under the throttle body where it bolts to the intake- this is a common place for these engines to leak coolant. I'd suggest that you check it both cold and hot- like Al said, some leaks only show up when cold- others only when hot... still others leak anytime.

 

[sciphi]

Also try replacing the radiator cap. A coolant leak on my 99 LeSabre (3800 Series II/4T65E) turned out to be a faulty radiator cap. This will have no effect if your leak is elsewhere.

 

[jdeare]

Thanks guys, I'm on it. The radiator cap was replaced last summer with the coolant, but I'll still check it out.

 

[lght1]

Hi

I have had extensive life experiences with the L36/L67 3800s and I will say that the orig. OEM LIM gaskets were plastic and prone to failure esp when used with OAT coolant.

When I repair one of these, I use the GM Aluminum framed LIM gaskets and use a silicated antifreeze . Most of the time, its G-05 or one of its clones..Mopar "Long Life" or Ford's "Gold" coolant, but today, I used a low silicate store brand as it was the best non OAT I could get. ( I installed a ported and polished LIM in my L36).

Fel-Pro now makes a alum framed LIM gasket as well for the 3800 SII L36/L67.


BTW, when replacing the UIM of a L36, try the APN UIM as it uses a stainless steal bushing for the reduced diameter EGR chimney. Nice kit.