Interesting Leak!!! 1998 Eldorado

HollywoodCuz · #1 (**permalink**) 07-23-09, 05:14 PM

I went to check my coolant reservoir level the other day when changing my oil. I open the cap look in see that it needs some. Since I just got the car I then made the decision to flush and refill the coolant on another day. So I put the cap back on and when I go down to put on my oil filter I see a big spot on the ground. Turn out its coolant.

1998 Cadillac Eldorado
So here is the problem
When I open the reservoir cap AND ONLY WHEN I open the reservoir cap it begins to leak coolant from behind and above the thermostat housing. I check the housing itself and it does not show signs of leaking and I haven't yet taken stuff apart to get to it, well I did remove the covers and the air cleaner to get a better look but no bolts. It does not leak when the reservoir cap is on or when the motor is running at Temp or at start up. Has anyone ever heard of this? I'm thinking(hoping) a gasket or something that is not to serious. Other than that the car runs great it has 100k miles in great condition.

Also it does not overheat or reached low enough level to turn on the low coolant light

**Ranger** · #2 (**permalink**) 07-23-09, 06:05 PM

I can't imagine what would leak when the cap is removed but not under pressure. Maybe a picture would help.

HollywoodCuz · #3 (**permalink**) 07-23-09, 06:17 PM

Ok i took some pics I will insert arrows to show exactly what I mean

HollywoodCuz · #4 (**permalink**) 07-23-09, 07:11 PM

these are the pics
remember. Only when I remove the cap in the first picture does it leak. Otherwise whether off, running at startup or regular Temp it does not leak.

SPreston2001 · #5 (**permalink**) 07-23-09, 07:26 PM

Water pump?

HollywoodCuz · #6 (**permalink**) 07-23-09, 07:27 PM

I believe that water pump is on the belt side

submariner409 · #7 (**permalink**) 07-23-09, 07:43 PM

The water pump is right next to the thermostat housing (your pictures) and is driven by that belt off the front head intake cam snout - it uses a ribbed plastic cam pulley, a spring loaded tensioner, and ribbed water pump pulley. Small 3-rib belt. Right behind your oil dipstick - that stamped black steel cover.......The correct coolant level is halfway up in the tank, COLD. No more.

The leak is mysterious, because even the surge tank overflow wouldn't be there, and the system purge line (from the top edge of the surge tank to the tit on the thermostat housing - a hollow bolt) is part of the sealed system.

There's a redesigned thermostat housing and seal - maybe that's your solution.

**Ranger** · #8 (**permalink**) 07-23-09, 10:19 PM

If it is leaking from behind (on the belt side) it can be nothing other than the pump seal or the shaft seal. That said, I still cannot understand why it would only leak with the cap removed and not while under pressure.

toomanytoyz · #9 (**permalink**) 09-27-09, 05:01 PM

I'm having a similar leak with my wife's 2003 STS. It just started this week and I noticed it when I was replacing the air pump with the upgraded one. It's leaking in the same spot as the OP's was. I'm not at all familiar with these N* motors, though I am very good with a traditional GM motor. Am I to believe that that is the themostat housing I am looking it? I had supposed it was, but wasn't quite sure. This is the first thread I came upon with pics while searching for an answer. So the water pump is on the back side (driver's side) of the motor, not the accessory side? Could that be the WP I'm looking at in those pics?

Whatever it is, the bottom part of that housing, up behind it, is what's wet. So apparently the gasket or RTV has failed in that spot. What exactly is it? So I know what to get?

It's just hard to be absolutely sure because (1) it's a frikken Northstar and (2) there is so much crap in the way that I can't see what it is! I have the airbox and PCM out of the way, the upper beauty plastics, and the lower bumper/subframe plastic cover off and half the driver's side wheelwell out to try to get a good angle and I just haven't been able to! I can only see two fasteners for that housing, too... Grrrrrr. I assume that once I am committed to making this repair, that I can remove the radiator and gain a bit more access... Maybe?

Somebody please tell me what I'm looking at! And is there a good writeup somewhere on how to repair this? Please help the N* Newb!

TIA!

**Ranger** · #10 (**permalink**) 09-27-09, 05:42 PM

Look at picture #3 above. See that black shroud between the torques strut (dog bone) and the dip stick. That shroud is protecting the water pump drive belt. You can just barely see the drive pulley off of the intake cam beneath it. Look farther down with a flashlight and you should be able to see the water pump pulley.

submariner409 · #11 (**permalink**) 09-27-09, 07:35 PM

toomany, In your STS the water pump, belt, tensioner, and drive pulley are under the black cover posted by Ranger - yes, on the rear or driver's end of the engine. Once you remove the shroud, plastic radiator sight cover, A.I.R. valve, thermostat cover, and hoses, the water pump capsule (it's all one piece: shaft, pulley, seals, impeller) comes out by using a special socket and retainer strap. You turn the capsule clockwise a quarter turn to unlock it. Takes a bit of force. There's an updated thermostat housing cover. Dealer. Replace the tensioner assembly and belt while you're in there. The main w/p drive pulley is tightly pressed onto the front intake cam snout. Don't mess with it.

Do a lot of homework in here and in Northstar Performance: There's a bit more to draining, capsule removal, replacement, and refilling of the cooling system than meets the eye. All the procedures are in here.

toomanytoyz · #12 (**permalink**) 09-27-09, 08:06 PM

Thanks guys. Yeah, since I was there, I ended up taking it all apart. I tried with the Autozone tool and it's a useless POS. As soon as I get enough torque on it to where the engine starts to rock on its mounts, it slips off the teeth. I need to get the one with the bolt on backing plate to get that pump out, methinks.

And I did do a lot more searching after this post and found a bit more info. I went back to almost 2005 in the Seville and tech tips section, but didn;t find many pics to help me along. I did, however, find a link to a library listing that had almost a complete FSM in it. Pretty cool. I printed that out and it helped.

Funny thing, aside from that tool, the only other wrench I used was a 10mm! lol

I do plan to get at least the eggplant shaped o-ring for the housing, if not a complete unit if I can find it. AZ didn't have it, but that comes as a shock to NOBODY!

Thanks for the tips. And wish me luck for tomorrow!

submariner409 · #13 (**permalink**) 09-27-09, 08:13 PM

Hey !!! If you can't find the rental socket with the retainer strap, get a gorilla buddy, a fender cover, and a six pack. Have him push on the wrench-socket assembly while you turn it.

Note well where the pump capsule tangs were when it comes out, and start the new one in the same orientation - it will take another magic words session to crank it, counterclockwise, back into position.

**Ranger** · #14 (**permalink**) 09-27-09, 08:25 PM

A few short bursts from an impact wrench seems to go a lot farther than increasing the torque on a ratchet.

toomanytoyz · #15 (**permalink**) 09-27-09, 11:24 PM

Quote:

Originally Posted by Ranger

A few short bursts from an impact wrench seems to go a lot farther than increasing the torque on a ratchet.

I thought that, too... But thought it might be overkill. And the fact that I thought I might destroy that stamped, cheapo, tool! Good to know it's an option. Might try it tomorrow before I go running around trying to find the other tool.

Anyone know who may carry (in stock) that thermostat housing to crossover o-ring?