'02 Impala (3.4L) Intake Project Complete, but

'02 Impala (3.4L) Intake Project Complete, but…

It’s done and seems to be running fine - smooth idle, heats up to about 185-192, new T-Stat appears to be opening OK … BUT I drove it 30 miles to work today and could smell a very faint whiff of coolant inside the car with Outside Air flowing throught the vents. I’ve looked several times for leaks but so far cannot see any. You’d think that if there was a leak while driving that you’d still be able to detect it after pulling over and shutting off the car. Maybe I need to leave the car running after stopping …

Also, I haven’t been able to get more than, say, 6-7 quarts of antifreeze/water mix into the car (a jug and a half) - even after bleeding at the T-Stat and leaving the radiator and tank caps off (and trying to fill after the T-Stat opened)! I could’ve sworn the system was bone dry when I opened it up - never saw any coolant spill out anywhere after emptying the radiator. When I started it up for the first time, I was getting the Low Coolant messages, but as I bled and filled it those went away and haven’t returned (I DID remove and clean the radiator sensor). I also overfilled the plastic tank (at, or even slightly above, the HOT line) thinking that I’d be pouring in AT LEAST two full jugs and it would bubble down, but it hasn’t gone down much. Pretty weird! After the drive to work today I tried to pour more in at noontime, but same thing - just a few tablespoons until the filler neck started to overflow. So I guess it’s full!

So should I flush and fill the coolant again - like I will be doing with the oil in a couple of weeks - since there apparently is contaminated coolant still inside?

Hello Colt Hero,

What’s the mileage now? 170hp V6?

That cooling system should hold at least 9.5 quarts.

When you had the intake manifold off did you remove the remaining coolant?

If not, that may be the reason for not being able to add more than you have.

FYI, don’t add more coolant to the reservoir than to fill it to the Full Cold mark.

Then, if there’s no leaks and the level has dropped, top it off to that level again.

Aside from that I can only suggest there may still be air in the system preventing you from topping it off.

You mentioned the operating temp is about 185 to 192F. That leads me to think you installed a 180F t-stat, right? So, if it doesn’t overheat, it must be circulating properly.

BTW, you only top up the coolant level by adding to the coolant reservoir ONLY. If the level is actually low, the engine recovery system will draw coolant from the reservoir as it cools.

Was the coolant slowly disappearing before you replaced the intake manifold gasket, or did you prevent internal leaks before it breached?

Your post seems to suggest there may still be contaminated coolant in the engine. If so, don’t drive it as the mix of coolant and engine oil will damage the bearings.

You can be sure that there was some coolant left in the engine. Unless you pick the engine up from the rear and tip it forward, quite a bit of coolant will remain in the block, plus some in the heater core and hoses. If it’s not overheating and hasn’t gone down for a week, it’s full.

Hi Roadrunner - great to hear from you again.

I’m at 105k right now with the mileage. Not sure what the horsepower is on this car. Doesn’t seem to be any stronger than it was previously (even though some people have claimed more power after the intake repair).

The manual says 11.7 Qts (I believe it was) for the cooling system. I mixed and poured in a full 50/50 jug plus half of a second. That’s about 6 Qts. Hard to believe there might’ve been 5 Qts left in the block - especially after removing every hose, the T-Stat, and digging into the center of the engine and not seeing any dribble out. And no - I didn’t “remove” any coolant when I had the intake out. How’s that done, with a siphon?

I know you’re not supposed to fill past the COLD mark on the plastic tank because the fluid expands up to the HOT mark and contracts back down to the COLD mark, but I made the mistake of assuming the system was almost bone dry and I would ultimately be adding AT LEAST 8 Qts, so after pouring the first 4 Qts. into the radiator, I poured maybe a little too much into the plastic tank, I guess…

I thought it might be air, too - but every time I opened the bleed screw on the T-STat housing, I got a stream of coolant out, so I closed it. I’m starting to think it’s full (maybe overfull). But that’s OK because I’m going to flush it again when I do the oil change. The residual coolant in the block probably still contains some residual oil (since the oil was definitely leaching into the coolant) and I need to get that out of there.

I don’t have the part number of the T-Stat I installed in front of me, but it’s the OEM part from the dealer. I’m usually very careful, but for this part I didn’t verify the number as being identical to what came out (should’ve done that b/c I think there are two different T-Stats for this engine). Instead, I just did a visual compare. What I can say is the temp gauge definitely reacts differently now. The car heats up on the temp scale MUCH QUICKER. Pretty much right after startup the engine, the temp gauge goes straight to 185-192 (just below the 200 mid scale) where it sticks until I come to a stop light. Then, it drifts toward 200 - maybe a little over that, before it cools back down (with the fans ON). With the old T-Stat, the temp would come up MUCH SLOWER - possibly because it was contaminated with oil and was always partially stuck open.

Yeah, I know you only top up at the reservoir, but when the system is bone dry I normally fill up the radiator first. Is there a problem with doing that?

The coolant was slowly disappearing (VERY SLOWLY). I had the fudgicle sludge on the backside of the radiator cap, and the plastic tank was greasy-looking. I also had poured some dye into the radiator and subsequently saw it bubble out the side of the block behind the Power Steering pump. This finally convinced me I had a problem. As it turned out, the PS side was the weakest area on my engine. The coolant passages were gunked up with oil on the inside and there was a muddy mix of sand and coolant mixed together on the outside. On the driver’s side of the engine, these analogous areas actually looked pretty good. The original gaskets themselves actually looked pretty good, too. I didn’t see any breaks or inclusions in the seals, but they looked fairly flat compared to the new Fel-Pros.

I’m not sure much coolant ever got into the oil. I never saw any in my oil whenever I did my oil changes every 3k miles (even with the dye in the coolant). But I KNOW oil was leaching into the coolant. With the new gaskets, I’m hoping that’s not happening anymore. However, as I stated above, if I really never fully drained the engine before beginning the intake gasket replacement, there still might be some trace amounts of oil in this residual coolant. This is why I’ll probably do another flush when I change the oil in a couple weeks.

What mr josh says is probably the case.

If the book says 11.7 qts you must have the rear climate control (A/C).

I doubt you’d be able to reach all the nooks and crannies to get all the coolant out even with a siphon.

If it isn’t too difficult, you might want to drop the oil pan (use a new gasket) and wipe it dry to make sure you get all the mixed oil/coolant out of it at least.

If you do, you can eyeball the crank for excessive wear and pitmarks.

It IS quite hard to remove all the sludge from the engine even by flushing.

Boiling the block would do it, but that’s only feasible if you’re rebuilding the complete engine.

My only concern in this instance is to remove as much sludge as possible to save the crank bearings.

Do you hear any strange noises from the engine when it is at operating temp? If not, you should be alright.

No problem filling the rad directly when refilling an empty cooling system.

You only need to fill the reservoir to the Full Cold mark when the rest of the system is full (and hopefully, not with air).

I went through this hassle when the gasket in my 2000 Silhouette 3.4L started to leak.

I had researched this van and the IMG problem intensively before I bought it so I had a head start on the fault.

The gasket didn’t start leaking until 5 months after I bought it. (three year off-lease with 40k miles)

My neighbor teased me about constantly checking the coolant level and looking for leaks, saying I was going to wear the hood hinges out before the engine.

I caught the leak starting to appear at one of the manifold corner bolts and that’s when I had my tech replace it for me. That was in Feb.'04, and have had no problems since.

Other things, but mostly preventive maintenance stuff like new rotors and pads yesterday, along with the regular oil and filter change.


Nope, no rear climate control on this car. And I’m pretty certain I read the manual correctly. I’ve flushed this car a few times before. It’s supposed to hold 11+ Qts.

No strange noises. It’s very smooth and quiet. Idles very low and smooth, too. Almost too good to be true. I checked for leaks again today after getting to work, but again I didn’t see any. Could’ve sworn I smelled a whiff or two of coolant while driving in, though. Maybe it’s all in my head. Hope so, anyway.

Hmmm…dropping the oil pan to wipe it dry…might want to do that. I’ve noticed with recent oil changes that the exterior of the pan glistens with oil. I wipe it off each time, but this is probably the gasket above. Might be a good excuse to tear into it…

When the oil pan looks moist it may be from the gasket ‘sweating’.

My pan gasket area is damp all the time but does not leak down the pan.

The cost to replace the oil pan gasket on this van empties the wallet. (Unless you can do the work yourself)

There is a lot of crap to remove to even get at the pan bolts. Same labor and cost as the intake manifold gasket replacement!
I don’t work on my vehicles to that degree anymore, so when I asked my tech how much and he said the same as the IMG job, I damn near freaked.

YOW! As far as I’m concerned that pan gasket can sweat forever as long as it doesn’t actually leak to the ground. So far it hasn’t.

When I buy a vehicle I try to take into consideration the upkeep and maintenance costs, but I didn’t see that one coming.
Then again, you can’t always forecast a tranny failure either.

You mentioned you get a periodic whiff of coolant. Perhaps there is a hose clamp loose on a heater pipe/hose fitting OR maybe a very slight heater core leak? (God forbid)

One thing you can try to stop the oil seepage from the gasket, is to re-torque the pan bolts, BUT, use a good quality torque wrench and stick to the proper tightening sequence so as not to warp the pan.


I think the coolant whiff has faded away. I checked all the hoses for three days and couldn’t see any obvious leaks. I guess it’s OK. But I turned the car over to the wife today, so we’ll see what she says about it (I didn’t say anything to her about it).

Don’t know when (or if) I’ll get around to the oil pan gasket. Will probably wait for it to hit the ground.