Thermostat Question - Page 2 - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


1992-1999 Series I L27 (1992-1994 SE,SLE, SSE) & Series II L36 (1995-1999 SE, SSE, SLE) and common problems for the Series I and II L67 (all supercharged models 92-99) Including Olds 88's, Olds LSS's and Buick Lesabres Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.

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Old 08-08-2004, 06:32 PM   #11
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Lemme elaborate so there'* no confusion...

Any time you put a cooler t-stat in you have to have your fans come on earlier or you wasted your effort. The fans and coolant have to work together to keep the engine at a given temperature. Only putting a 180 t-stat in will still result in normal temps around town and only making the fans come on at 180 will still result in normal temps no matter what. The fans aren't very powerful and not capable of changing engine temps on their own. They're designed to come on if coolant is not enough which 90% of the time it isn't. There are three ways of going about this properly. Listed is cheapest to most expensive:

1. 180 T-stat with a switch and relay to manually turn the fans on. This is OK (its what I do) but you risk overheating your engine if you forget to turn the fans on. Not the best way but at a couple bucks for the switch, relay, and wires its the cheapest.

2. 180 T-stat with the adjustable fan t-stat I posted above. This can work because the computer (as far as the fans go) ignores the temperature until it hits 220 or so. Since you set this to come on at about 200 it'll think the coolant is taking care of things. If you wire it right the computer can act like a safety backup. If for some reason the adjustable t-stat goes out, the computer will still turn them on at 220 saving you from overheating.

3. 180 T-stat with Custom PCM. This isn't something you probably wanna do just to adjust your temperature but if you're getting it anyway you can have that added in.
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Old 08-08-2004, 07:20 PM   #12
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Before next summer i'm gonna get that fan kit.

Lots of stuff in summit works for these cars, i read the catalog a lot looking for new ideas.
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Old 08-09-2004, 10:15 PM   #13
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Quote:
Originally Posted by willwren
There'* been some controversy on the 99 intakes. I'm not sure I've seen one fail yet, but it may have to do with the production date.
My intake failed. Real bad too. 99 car, but the intake itself?...
Just so happens, I kept the old intake as a relic. Date: 10-07-98. So, you're right there - it is still a 98.
But get this: It'* Delphi. Now what? I thought they switched to Delphi from Rochester. Or is it that the Delphi was also bad, but was improved?
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Old 08-10-2004, 12:48 AM   #14
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my goodness. like i said, i have a one month warranty on my new bonnie. is there any way i can check to see if the intake is on it'* way to failing and get it fixed before my warranty goes out? also, i've been driving it around for a few days now and have kept a close eye on the temp and it has yet to reach 200. i imagine that'* a good sign, correct?
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Old 08-10-2004, 07:52 AM   #15
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Quote:
Originally Posted by jr's3800
I would appreciate it if you would look in the 92-99 section, and post more information on the upper intake failure... This is very usable information for all of us here..

Also if you don't mind, would it be possible for you to e-mail me the highest grade pics of the intake if possible...

I have a 99 intake on my car as I had a failure in 99... So I am wondering... Thanks..

Sorry for hijacking the thread guys...
I will do that. As for the pics, I will as soon as I get my hands on a digital camera, which I hope will be soon.

Note to Strangelove: mine failed at about 95K, but like everyone says around here, it can happen sooner. It'* scary because, although many people seem to report that they catch it and crank out the coolant, make the repair, and everything'* fine, with mine: complete failure, no crank. no more motor.
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Old 08-10-2004, 08:11 AM   #16
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Quote:
Originally Posted by Strangelove
is there any way i can check to see if the intake is on it'* way to failing and get it fixed before my warranty goes out?
The other day I was asking the same thing - can it be checked. I asked my mechanic what it would take to check it money-wise. Because you need to crush new gaskets, and what with labor...: I was quoted about $250 - just to check it mind you (I'm in NJ - I would consider that a high$ location, but anyway... ) I guess then you'd physically check the passages to insure that there was no deterioration at the crucial points.
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Old 08-10-2004, 08:46 AM   #17
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I've said this time and time again....

Please don't underestimate the likelihood of the lower gaskets failing! IMO the lower gaskets are what causes the upper intake to fail. I highly recommend replacing your lower gaskets at the same time that you change your upper intake manifold.

At 76K miles my upper intake was 100% fine (no degradation whatsoever). However, the lower gaskets were severly deformed.
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Old 08-10-2004, 11:11 AM   #18
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ok, i think i got this. the only reason that the lower gaskets or upper intakes fail is because there is a plastic pipe carrying coolant right next to a heat pipe that melts and causes coolatn to get in the engine. if you can keep the engine cool enough, you can greatly reduce the chances of the plastic coolant line melting and thus the lower gaskets or upper intakes getting messed up. if you can catch it early, it'* only a few hundred dollar repair. if you catch it late, it'* over a grand. is that about right?
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Old 08-10-2004, 11:38 AM   #19
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That'* our general feeling here. It'* one of the reasons we suggest the 180 thermostat (preferably drilled).

There is a way to identify the 'old' and 'new' designs of the intake by removing the EGR stovepipe. I think there'* pics in that sticky VinK post?
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Old 08-10-2004, 12:26 PM   #20
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To Strangelove, Let me see if I can explain this carefully:
-The air Plenum is the big black plastic part on top (just under you gray engine cover)
-The Intake Manifold is the aluminum part underneath the plenum, and bolts to both cylinder heads.

The "lower gaskets" (two of them) are between the intake manifold and the cylinder heads. (-they seal each intake port, and also, separately, each cylinder head coolant port). I don't know if anyone really knows why these lower gaskets are failing. I have no reason to believe that their failure is in any way associated with the plenum failure. Also, -meaning absolutely NO OFFENSE TO ANYONE, I really have my doubts that having the thermostat open 15 degrees sooner will help at all. -but, I suppose it can't hurt either. The actual engine internal operating temperatures going down the road will still stabilize somewhere in the 200 degree range.

The Plenum is failing because the original factory design plumbs the EGR (exhaust gas recirculation) pipe up through the plenum floor, just inside of the throttle body mounting area. There is direct contact between that VERY HOT EGR pipe and the plenum plastic, resulting in deterioration of the plastic. As the plastic deterioration continues to grow in area, it soon works it'* way into a coolant passage that is close by. And then due to engine vacuum and intake air flow, coolant begins to get sucked into the plenum, manifold, cylinder head ports, combustion chambers, etc.

And once again, with no offense to anyone, I see absolutely no way that opening the thermostat 15 degrees sooner is going to help anything. The exhaust gas temperature is still WAY TOO HOT for plastic to survive.

In my experienced opinion, the ONLY WAY to stop the plastic deterioriation is to get the heat away from it. There is a kit on the market that does just that. My experience in using the kit was as perfect as it gets. Others have reported pure hell in trying to use the kit. -so take your pick. Also, others are in the process of machining out the parts to make their own modification kit.

Hope this helps !!
There are many many excellent users on this forum with excellent advice, and are sharing their "first hand experiences." This is good.
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