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Discussion Starter #1
Ok - I've got a '92 Seville, 124K on the clock. On occasion it overheats - when it does it pushes coolant out of the recovery tank. Now I've been around the block on this one - and the following has been done to date.

1) waterpump, thermostat and radiator cap replaced
2) radiator rebuilt (tank removed, core rodded out, new tank installed) - prior to having this done, the shop "sniffed" the coolant to see if a head gasket was compromised and it came back negative. They also did a compression check with a max of 6% difference (as I recall) between cylinders and an average (again, from memory) compression reading of around 180 PSI - again indicating that the head gaskets were fine.
3) cooling system flushed and re-filled (with anti-foam in the new coolant) - after the temp "spiked" once following item #2.

Yesterday (right after the flush) and this morning it ran fine - nice and cool (considering that it was 15 degrees out this morning, I guess that could be expected!) but driving from a meeting to the office it did the following:

coolant temp was 164 degrees - I saw steam coming from under the hood
coolant temp rose to 260 (I was in traffic - no place to pull over)
I gassed it onto the highway coolant temp dropped to 206 - eventually rose to 210 again - but was fine until I hit the office. I popped the hood and the coolant recovery tank was full. Also - when it gets hot I have no heat (which is sort of counter-intuitive).

Something is blocking the flow in the coolant system - if it's not a head gasket, it's not the thermostat (which I checked in a pot of boiling water prior to installation) and it's not the radiator (which flows fine following it's cleaning) does anyone have an idea as to what it can be???

It's not an "everytime" thing - the car will go fine for a week or so and act up perhaps once - and it's driven every day.

Is there a check valve in the system somewhere that I'm missing? Is the 4.9 like a friend of mines Jag engine where there is a water pump just for the heater core? This thing is driving me nuts - it's actually making me consider going back to driving a jeep (I think I can buy my old CJ-5 back from the guy I sold it to) and to hell with the caddy - but I'd hate to take that step for a number of reasons.

This is quite frustrating - I don't ask much of a vehicle - just that it get me to and from work and other places I need to be - any ideas or thoughts will be appreciated.

Thanks in advance

Steve
 

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2005 Escalade 6.0L 2WD, 2007 Jeep Grand Cherokee Limited CRD
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Check that the passage under the radiator cap to the coolant resevoir isn't plugged up. That happened on my '94 Deville, and it did just what you said! It overheated, and all the coolant was coming out of the overflow tank, and the radiator was low on coolant.
 

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94 Eldorado, and a 99 ETC
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What comes to my mind is that maybe the water pump froze up for a second, causing the flow to stop, and also the belt to 'burn rubber' on the pully causing the smoke. Then when you reved the engine, it gave enough force to get the pump unstuck for the rest of the ride.

Thats just my hypothesis though.

Was your replacement waterpump OEM?
 

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White Diamond '03 DHS (with DTS floor shift)
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Keep in mind that a "compression test" does not rule out a bad head gasket. It will rule out a burnt valve. You need to have a "cylinder leak down" test done to confirm a head gasket. Not sure what a "sniff" test is. If it is what I think, I'd opt for the leak down test. I'm not saying that this is a head gasket problem, just trying to clarify a point.
 

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13 Challenger RT, 11 CTS Coupe Premium, 94 Eldorado (RIP)
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I would idle it in the driveway and check for leaks that may have caused that steam. Your overflow does have a hose going to under the vehicle, correct?

Check out the water pump belt. Like Krashed said, it may have been smoke instead of steam.

While you are checking all this, the temp will be getting up there. Check you fans, like Dadillac mentioned. See if they come on when they should.
 

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Discussion Starter #7
Well, here's the deal so far. I checked the overflow tank using a suction pump (I know the coolant is getting INTO the tank under pressure) and the coolant trickled back to the radiator SO I pulled the tank and the hose (made all the more convenient by having to remove the cross-brace first) - turns out that someone (must have been the previous owner, 'cause I don't touch the stuff) put "bars-leak" into the overflow tank. There was a big "goober" (for lack of a better term) of the junk that would block the passage to the hose that went back to the radiator - so it was like a roach motel - coolant could check in BUT it couldn't check out. I cleaned out the overflow tank and replaced the hose.
In addition - I think that the serp belt tensioner is shot - to me it doesn't feel like there's enough tension on the belt (I can, using reasonable pressure, push the belt in about an inch - and watch the tensioner move when I do this - I cannot do that on the wifes Neon) so this weekend is new tensioner and new belt time. I've also noticed that the waterpump "pulley" appears to be out of balance - I get slight wobble when the engine is at idle. I doubt this is of any significance since the seal on the shaft isn't leaking - the pulley did not seem to be eccentric when I looked at it prior to re-installation and the "wobble" is not significant - probably less than 1/64 of an inch total rotational movement).
The waterpump was a rebuilt OEM unit. I installed it probably two months ago. The original was all clogged up with stop leak or some other junk. Apparently the previous owner used stop-leak (the stuff that looks like rabbit crap floating in old coffee) in lieu of the GM tabs. As an aside, the shop that did the flush indicated that a lot of "black crap" came out during the flush. The folks who did my radiator described the same "stuff" clogging the radiator tank on the inlet side.
My overflow tank does not "vent under the car" - it only vents through the hole in the cap on top of it. This appears to be a stock configuration.
My primary fan (the one that runs when the AC is not on) appears - at least to me - to be a "fan of leisure" - it comes on when the temp hits about 220 BUT doesn't exactly run like a gangbuster - unless it's a two stage DC motor (which I doubt) I believe that it's checking out - so that will be another part for me to replace. I'll probably just replace the motor (one nice thing about working as a mechanical engineer is that I have access to all sorts of "neat stuff" when it comes to servos, motors and the like - actually I guess everyone has access to them - just hit the mcmaster-carr website - my advantage is having access to (and a good working relationship with) some really sharp fabrication shops)
This morning all seemed well on my 25 mile commute - given that the roads were snow covered I couldn't exactly "open her up" but we held at a nice steady 197 degrees - with a 195 degree thermostat. I checked the overflow tank when I arrived at the office and it was at the same level as when I left my home, which I consider to be a good thing. I just re-checked (had to move my car so the parking lot could be cleared) and the level is the same (used a sharpie to mark the level last night so the evaluation wouldn't be totally subjective or based on memory, which seems to be failing from time to time as I get older).
I suspect that the stop leak clogs were part of the reason that the cooling system was such a pain to "bleed" free of air.
The previous owner also installed a "T" fitting in the heater core hose which I will be eliminating this weekend - to me it's just a non-OEM opportunity for an air or fluid leak. A "spray pattern" on the hood blanket and firewall above and behind this "T" provide graphic evidence of a leak at some time - although I've not witnessed any leaks while working on the engine -
Thanks for the help and suggestions - I'll post if anything changes.

Steve
 

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Hi Steve: Hope you read this before you get home today. On your way home stop and get a water pump belt tentioner assembly and plan on replacing your old one this weekend. Why? The center of the follower ring is a bakelite material and will fail at about your milage and is accelerated by overheating. When that happens; no belt tentsion and no cooling and lots of messages and rapid overheating. Happen to me and you mentioned a "wobble" on the belt.
I also am chasing a coolent loss problem and have replaced all the items you did except the tentioner assembly. Found out about that the hard way.


Good luck
 

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Very nice description of the gunk, especially the roach motel part. You always have the cracks.

Good to hear you are making progress. Sounds to me like the previous owner got carried away with that stop leak.
 

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Discussion Starter #10
to both eldyfig and windrider - and all who offered suggestions - thanks much - I was planning on replacing the serp belt and tensioner this weekend - in fact both are in the trunk of the car as I write this.

As for the stop leak - I'm curious myself as to why so much of it was used - I keep waiting for "old faithful" to rear it's ugly head in the heater core or something - I mean you'd think there had to be some reason all that stop leak was used - but the radiator doesn't leak - it almost looks like they used three or four bottles of it in lieu of three or four GM tabs ..... who knows what evil lurks in the minds of men (the shadow knows!).

Glad you appreciated my descriptions - I'm known around the office for having a "unique" way of describing people, places, sounds and things (on occasion it's a good reputation to have but you do have to take care around certain people who don't appreciate sarcastic SOB's).

Well, 43 minutes until I head for home and replace the tensioner and belt - have a great weekend and thanks again!

Steve
 
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