Any theories out there?

[iceman2]

Just thought I'd offer my two cents. After struggling through the head/intake gaskets replacement operation for the last several weekends, (and finishing successfully, so far) can anyone offer a logical explanation as to why these things are failing? I am no where close to an expert, but IMHO, there might be two possible culprits, the anti-freeze debate and the motor mounts attached to the heads. When I drained the cooling system this weekend, I noticed the previous owner had put in the green stuff which was mixed with the orange stuff, and from what I've been reading, that's a definite no-go, also, the heads have motor mounts, as well as the alt and PS pump, attached directly, and I would think the excess vibration of the engine, especially in reverse, would put excessive stress on the heads, FWIW.

[Sparky1349]

Originally Posted by iceman2

Just thought I'd offer my two cents. After struggling through the head/intake gaskets replacement operation for the last several weekends, (and finishing successfully, so far) can anyone offer a logical explanation as to why these things are failing? I am no where close to an expert, but IMHO, there might be two possible culprits, the anti-freeze debate and the motor mounts attached to the heads. When I drained the cooling system this weekend, I noticed the previous owner had put in the green stuff which was mixed with the orange stuff, and from what I've been reading, that's a definite no-go, also, the heads have motor mounts, as well as the alt and PS pump, attached directly, and I would think the excess vibration of the engine, especially in reverse, would put excessive stress on the heads, FWIW.

Hey Iceman, I have a theory that the design of the intake manifold gaskets weren't capable of sealing the cooling system passages when there is insufficient clamping force. The clamping force issue is the TCE (thermal coefficient of expansion) mismatch between the steel bolts and the aluminum heads and manifold. As the heads and intake go through multiple thermal cycles the bolts gradually back off especially the corner bolts, hence the GM replacement bolts with integral locktite. The corner bolts on my van only needed about an 1/8 of a turn before they could be loosened by hand. Luckily for me most of the coolant went on the ground and not into the engine, no brown milkshake goo in the engine when I took it apart.

The motor mounts on the cylinder head aren't that much of a factor since the passenger side only has 1 bolt that goes into the head and the drivers side only has 2 or 3 that bolt to the end of the head (perpendicular to the intake sealing surface), in addition both mounts are rubber mounted so vibration going into the head is minimized. I don't know if the PS Pump and Alternator are as much of a vibration issue as a heat source issue, higher temperatures are more likely to cause expansion/contraction problems.

Intake manifold gaskets are the second most difficult sealing problem in an engine (specifically a V configuration) with the head gaskets being number 1. If the engine manufacturer/designer doesn't pay adequate attention then they wind up with these nagging issues that take several model years to straighten out.

It is very dissapointing that GM won't stand behind their product and repair these as a campaign or program. I understand that GM is having a lot of financial problems but they are being very short sighted about the way they are treating their customers. The may save a few bucks by not fixing these but in the long run they are losing customers, I know that I will have a hard time deciding what to buy the next time around. I have never bought a Jap car before but now I think I have to consider it.

Sorry this got a little long winded, I always get wordy when I'm P.O'd.

Sparky

[iceman2]

Originally Posted by Sparky1349

Hey Iceman, I have a theory that the design of the intake manifold gaskets weren't capable of sealing the cooling system passages when there is insufficient clamping force. The clamping force issue is the TCE (thermal coefficient of expansion) mismatch between the steel bolts and the aluminum heads and manifold. As the heads and intake go through multiple thermal cycles the bolts gradually back off especially the corner bolts, hence the GM replacement bolts with integral locktite. The corner bolts on my van only needed about an 1/8 of a turn before they could be loosened by hand. Luckily for me most of the coolant went on the ground and not into the engine, no brown milkshake goo in the engine when I took it apart.

The motor mounts on the cylinder head aren't that much of a factor since the passenger side only has 1 bolt that goes into the head and the drivers side only has 2 or 3 that bolt to the end of the head (perpendicular to the intake sealing surface), in addition both mounts are rubber mounted so vibration going into the head is minimized. I don't know if the PS Pump and Alternator are as much of a vibration issue as a heat source issue, higher temperatures are more likely to cause expansion/contraction problems.

Intake manifold gaskets are the second most difficult sealing problem in an engine (specifically a V configuration) with the head gaskets being number 1. If the engine manufacturer/designer doesn't pay adequate attention then they wind up with these nagging issues that take several model years to straighten out.

It is very dissapointing that GM won't stand behind their product and repair these as a campaign or program. I understand that GM is having a lot of financial problems but they are being very short sighted about the way they are treating their customers. The may save a few bucks by not fixing these but in the long run they are losing customers, I know that I will have a hard time deciding what to buy the next time around. I have never bought a Jap car before but now I think I have to consider it.

Sorry this got a little long winded, I always get wordy when I'm P.O'd.

Sparky

Good insight, Spark, how's your effort on the IMG's going? I got mine all back together and it's running great! Couple of tweaks remain, I broke the outside portion of the radiator drain plug and want to replace it, although it doesn't leak, and I need to flush the cooling system (previous owner mixed green with orange, arrrgh!). The serpentine belt broke yesterday and I freaked cause I thought the AC might have seized - it did not- the belt was just ready to get replaced, which is about the only thing I found rather easy on this van. (BTW, try turning your van without power steering!) God forbid, but I'm leaning towards the Orange Dexcool, I always go with what the manufacturer recommends.

[Sparky1349]

Originally Posted by iceman2

Good insight, Spark, how's your effort on the IMG's going? I got mine all back together and it's running great! Couple of tweaks remain, I broke the outside portion of the radiator drain plug and want to replace it, although it doesn't leak, and I need to flush the cooling system (previous owner mixed green with orange, arrrgh!). The serpentine belt broke yesterday and I freaked cause I thought the AC might have seized - it did not- the belt was just ready to get replaced, which is about the only thing I found rather easy on this van. (BTW, try turning your van without power steering!) God forbid, but I'm leaning towards the Orange Dexcool, I always go with what the manufacturer recommends.

Hey Iceman,
Mine is back together and I turned it over to the wife. Only thing that is still a little freaky is how to get all of the air pockets out of the cooling system. The temp gauge is fine on the highway but when I was sitting idling in traffic it went up to 3/4 scale then dropped back to 1/2, never made it into the red but it made me kind of nervous. I am leaning towards the cooling system extractor but $100 is a little pricey. I might buy an R134 A/C vacuum pump from Ebay for $25 and make my own extractor system. Can't see any other way to get all of the air out of the upper radiator hose. I keep opening the 2 vents and getting a little air out each time but after I drive it the very top of the upper radiator hose is not getting as hot as the bottom so I am sure there is a bubble in there.

I agree about the Orange stuff, as long as you don't have any leaks (like an IMG) I don't think there is anything to worry about. The coolant on my Blazer was low and sure enough it plugged up the heater core with brown goo.

Bummer about your Serp Belt, at least for a transverse engine it is pretty easy to change, even with >50K Miles mine looks brand new.

The only other outstanding item is I broke the plastic vacuum pipe from the MAF to the fuel pressure regulator right at the rubber "T". For the time being I just shoved the tube back into the "T" after I fished the broken piece out. Seems to be working so far, but I should probably replace it.

Let me know how it goes with the flush and valve replacement.

Sparky

['97ventureowner]

Originally Posted by iceman2

Just thought I'd offer my two cents. After struggling through the head/intake gaskets replacement operation for the last several weekends, (and finishing successfully, so far) can anyone offer a logical explanation as to why these things are failing?

I read an interesting article a couple years back about the intake gasket problems and possible causes, and one thing that the author brought up was the thinness of the gasket. He thought that if GM had used a thicker gasket , than maybe there would not be so many problems. Another thing that was thought to be a cause was that the bolts maybe should have been torqued down more at assembly. The author had interviewed many mechanics and some had also mentioned if the gaskets had steel in them, they might have also lasted longer, and not failed. Still another theory floated around at that time was the change in "fluid technology". The author stated that sometimes when there is a major change in fluids ( i.e. the switch from ethylene glycol to Dex Cool) unforeseen problems can result that maybe could not be detected during the time leading up to the use of the new fluid,(trial results and research.) The author compared the problem with the intake gaskets to when synthetic oils were introduced and they were thought to cause shrinking gaskets and oil leakage in engines back then. He said it may take time for engineeers and developers to come up with a "fix" to correct the issue and make it work with the new fluid technologies. (Hence GM designing a new gasket in 2002- roughly 7 years after the problem was first reported.) To me that is too long of a time to come up with a "fix" to the original problem.
He also stated that we ( the engineers and developers among others,) can test and put things through thousands of trials and test runs, and not get any problems, but it's humanly impossible to predict what will happen in unique situations or over an extended period of time. To further this point, the author used the analogy of the gasket failure on the Space Shuttle which caused it to explode. NASA had tested those gaskets time and time again with good results, but could not predict the unforeseeables once it was put into "real world" use.

[iceman2]

'97ventureowner, based on your knowledge, would you recommend the green or orange coolant? I too, have a '97 that is currently holding a mixture of green, orange, and water, with new head and intake gaskets.

['97ventureowner]

I'm still using Dex Cool. I have changed my habits based on past research and am now changing and flushing the radiator every 2 to 2 1/2 years and between 30,000 and 40,000 miles,similar to the ethylene glycol (green antifreeze) recommendations of the past. The Dex Cool, being a different type of coolant (Organic Acid Technology,) than ethylene glycol is better suited for today's engines with the protection package it offers. I keep a vigilant eye on my coolant level and oil,( am also considering having my oil analyzed every 12 to 18 months on some of my vehicles.)If maintained properly, the Dex Cool should(and I say SHOULD) not be a problem, given that it is replaced on schedule, and there is no air infiltration into the cooling system, and the level is kept within range. I've been running Dex Cool for 10 years now and I just had the problem with the IMG on my Venture, which was replaced back in '02 with the updated version, and is still doing quite well. I purchased a 2006 Chevrolet Uplander last fall and that also has Dex Cool in the cooling system and I intend to keep it that way and maintain it to hopefully have no issues in the future.

[iceman2]

Well put, Dexcool it is, I will flush out the cooling system this weekend.

[Sparky1349]

Hey Guys, I found 2 very interesting web sites about Dex Cool (and coolants in general), The first one is from a trade group and the second one is from a trade show about a presentation from GM and Texaco (Maker of Dex-Cool), I checked for the video referenced in the second article to see if someone had posted it on YouTube.com but couldn't find it:

http://www.babcox.com/editorial/tr/tr110046.htm

http://www.imcool.com/articles/antifreeze-coolant/dexcool-macs2001.htm

I think the short version is that a vehicle using Dex-Cool with no other issues is OK, however when you have other deficient components like poor IMG design, inadequate intake manifold clamping force, poorly designed Radiator Caps (Like on my Blazer), air entrapment (upper radiator hose and heater hoses on Venture) the failure mechanism is catastrophic. What was that line about a slippery slope - same thing with Dex-Cool there are no little problems because as soon as you have a problem it is catastrophic.

I ordered a vacuum pump on Ebay, I am going to pump the cooling system down on the Venture getting every last molecule of air out if I can and then fill with a 50/50 mixture of Dex-Cool only because I don't want to try and flush every last drop of the old stuff out, then I'm going to keep a very close eye on it, very close!

Sparky

[iceman2]

Outstanding articles, Spark, now I don't know what to do, how do you use the bleeder screws? I believe I have two of them.

[Sparky1349]

Hey Iceman, According to what I have read the bleeder screws should be used at the initial fill to get as much coolant as possible into the system (i.e. to let the air bleed out of the system). After the initial fill the idea is to thermal cycle the engine and after cool down open the bleeder to allow trapped air to escape. Continue to do this proceedure until all the air is out.

I did this proceedure about 5 times and air was still coming out, so then I modified it. After cool down I opened the bleeder screw on the thermistat housing and squeezed the upper radiator hose as tight as I could by hand. Then closed the bleeder screw and topped off the radiator. I repeated this proceedure until I couldn't get anymore air out of the bleeder or any more coolant into the radiator. The I opened the bleeder on the bypass hose (on top of the water pump). Only liquid came out.

At this point I started the engine and let it warm up, the top of the upper radiator hose is still cool even though the bottom is warm/hot so I know there is still an air bubble in there. That's why I bought a vacuum pump on Ebay, I'm going to pump the cooling system down and vacuum fill it just like they do at the factory. I'll let you know how that works out when I get the pump.

Here is a commercial version of what I am trying to make for myself:
http://www.etoolcart.com/index.asp?P...OD&ProdID=3621

Or from Snap-on:

http://buy1.snapon.com/catalog/item....re&dir=catalog

Here is the cheapest one that I have found:
http://www.tooldiscounter.com/ItemDi...ndmail=getinfo


Sparky

[iceman2]

Thought I read somewhere that a properly working cooling system will eventually work all of the air out on its own?

[DRW1000]

Originally Posted by iceman2

Thought I read somewhere that a properly working cooling system will eventually work all of the air out on its own?

I only open the bleed valves when initially filling the rad. I then simply top up the overflow after the next 3 or drive cycles.