coolant flush?!

Hi, I have a 99 Chev lumina with the 3.8L engine.
On the weekend we were out late at night and had the heater on and it was blowing cold air. Despite the temp gage being right in the middle. (normal)
Then today we noticed the temp gage going up very high.
The temp was going back down to normal but would go back up again shortly after going to normal. So I am guessing that the thermostat is opening.


When I got home and popped the hood... the passengers side fan was running and the drivers side was not. Is this normal? Does it only come on if the temp goes even higher?

Anyway, the cold air blowing when the temp is normal tells me that there is Air in the system... is that right?

2nd, Should I do a complete flush of the system and replace my thermostat?

If so, can someone explain how do flush the system.

Thanks.
Hearts88

You better take a close look after filling it. You are probably leaking hard someplace. Seems like there was a plastic water neck on some of the 3.8's that would crack and dump all the coolant outta the top of the motor...it's on the passenger's side, behind the belt driven stuff, comes off the intake.

Sometimes it happens so suddenly, you never see the leak if it happens on the road...I've seen them come in with the neck cracked in two, and the hose hanging down.

Your temp was surging because there isn't enough coolant to keep the sensors or thermostat submerged. One fan is normal for routine engine cooling.

Just open the radiator (not the resevoir) and fill, then run it. I bet it starts leaking like crazy...

I agree with Jeff. Check the plastic elbow that goes from the belt tensioner assembly to the intake. If it's not leaking there, you may have a cracked upper plenum or bad upper plenum gasket and the coolant is leaking into the engine. Normally, a failed plenum gasket will also leak from where the throttle body mounts to the plenum.

I agree with Jeff. Check the plastic elbow that goes from the belt tensioner assembly to the intake. If it's not leaking there, you may have a cracked upper plenum or bad upper plenum gasket and the coolant is leaking into the engine. Normally, a failed plenum gasket will also leak from where the throttle body mounts to the plenum.

Okay, what I found is a small, plastic hose, that comes out of the engine block right above the water pump, and then 90degrees to where the belt tensioner is.
Is that what I am looking for?
what I got is a small drip from this hose at the block. Nothing major, however I guess if it has been leaking for a long time, that could be the low coolant problem.
How do I go about fixing/replacing it?
This is my wifes car, and I need to get her to stop driving my car!!!:evillol: if anyone can let me know asap that would be great!

Hearts88

Yes, that's what we're talking about. To replace it, you'll have to remove the tensioner assembly. They ( the plastic elbows) are available through Dorman or Motormite, and they are no different than the dealer part. They normally will only drip in the driveway, but once you get going down the road, they spray like a firehose. If you haven't changed the thermostat in a while (over a year) go ahead and change it while the cooling system is open.

Yes, that's what we're talking about. To replace it, you'll have to remove the tensioner assembly. They ( the plastic elbows) are available through Dorman or Motormite, and they are no different than the dealer part. They normally will only drip in the driveway, but once you get going down the road, they spray like a firehose. If you haven't changed the thermostat in a while (over a year) go ahead and change it while the cooling system is open.

Ok, so remove the tensioner assembly, and the plastic hose will come out of the block. It just has a seal on it. The 90degree from the tensioner keeps it in the block?

I'm up in Canada, so I have never heard of those places. Is this a common part or am I going to have to go to the dealer for this?
Unfortunatly here on Saturdays the good part stores are either closed or close at noon. There is "canadian Tire". A bunch of genious's there. I once called for an Alt and they said they had a 70amp and a 78amp.. I asked the differance and they said "8 amps" :screwy: You don't say... thanks for doing the math.
sorry venting.
So common part or should it be easy to find?

Thanks a ton for your help!
really appreciate it!
Hearts88

Yes, the tensioner is what holds it in. Dorman and Motorite are brand names, not store names, sorry for the confusion. Just about any auto parts store should either have them or be able to order them. I work tomorrow from 8am-3:30pm EDT (I'm in Michigan). If you need me to, I'll get the part numbers so you don't have to depend on those parts monkeys to try and look it up for you. I'd have been tempted to smack them for being that crass while answering your question about the alternator.

Yes, the tensioner is what holds it in. Dorman and Motorite are brand names, not store names, sorry for the confusion. Just about any auto parts store should either have them or be able to order them. I work tomorrow from 8am-3:30pm EDT (I'm in Michigan). If you need me to, I'll get the part numbers so you don't have to depend on those parts monkeys to try and look it up for you. I'd have been tempted to smack them for being that crass while answering your question about the alternator.

Hey Richtazz, thanks for all the help. I'm heading out to work on it today.
No parts store around here carries the part. Even the good parts store like Car Quest. Had to go to the dealer. $20 bucks... not bad... Even he wasn't sure what I was talking about. And they got that fancy computer with the 3D cutouts!!
Anyway, I'll let ya know how I make out.
Hearts88

You better take a close look after filling it. You are probably leaking hard someplace. Seems like there was a plastic water neck on some of the 3.8's that would crack and dump all the coolant outta the top of the motor...it's on the passenger's side, behind the belt driven stuff, comes off the intake.

Sometimes it happens so suddenly, you never see the leak if it happens on the road...I've seen them come in with the neck cracked in two, and the hose hanging down.

Your temp was surging because there isn't enough coolant to keep the sensors or thermostat submerged. One fan is normal for routine engine cooling.

Just open the radiator (not the resevoir) and fill, then run it. I bet it starts leaking like crazy...
ooo so that's why it does that. i've always watched my car for it to do that so i know when to add more coolant to it. is it safe for my car to use that as a gage as to when to add more since it leaks out so bad and i am constantly filling it up..

ooo so that's why it does that. i've always watched my car for it to do that so i know when to add more coolant to it. is it safe for my car to use that as a gage as to when to add more since it leaks out so bad and i am constantly filling it up..

It really needs to be bled whenever it's filled...where are you leaking from?

It really needs to be bled whenever it's filled...where are you leaking from?
umm...no clue..my dad doesn't think it's an issue we've gone thru 2 jugs of coolant in just a few months cuz of it. since he doesn't care i took it into the automotive class at school and they couldn't even figure out it was leaking coolant. i filled it up 3 times over the weekend i drove from WI to IA for my birthday 3 weeks ago and already it's out again.

any ideas where in there it could be leaking from? it's dirty so i don't really want to touch it myself..

Lower intake gaskets are typical for 3.1's...can leak externally or into the engine. You need to get it filled AND bled, then run it, and the leak will probably show itself...

If you have it in auto shop, pressurize the cooling system. You'll hear the air escaping from around the base of the intake if the gaskets are your issue.