OATs Swelling Headgaskets

JHZR2 · May 4, 2019

Many know I'm interested in head gaskets and coolants right now. I came upon the following article: http://www.zr1specialist.com/HAT%20...rms%20the%20Cylinder%20Head%20Gasket.pdf That implies that OAT coolants swell elements of HGs causing failure. This is from the LT5 from the C4 Corvette, a somewhat unique, outsourced engine. Of course I'm interested in diesels and mixed metal engines... but interested in others' thoughts on the article, findings and claims.

Chris142 · May 4, 2019

I think it depends on the materials used. The 5.3 in the trucks uses a metal gasket with a rubber or silicone seal around the ports. Those seals are always swelled and are often the reason for replacing the water pump.

JHZR2 · May 4, 2019

Originally Posted by Chris142

I think it depends on the materials used. The 5.3 in the trucks uses a metal gasket with a rubber or silicone seal around the ports. Those seals are always swelled and are often the reason for replacing the water pump.

Sorry, how does the HG construction affect the replacement of the WP? I'm just not familiar. In the linked paper, it was a metal coated HG of some kind it seems to me.

Chris142 · May 4, 2019

Originally Posted by JHZR2

Originally Posted by Chris142

I think it depends on the materials used. The 5.3 in the trucks uses a metal gasket with a rubber or silicone seal around the ports. Those seals are always swelled and are often the reason for replacing the water pump.

Sorry, how does the HG construction affect the replacement of the WP? I'm just not familiar. In the linked paper, it was a metal coated HG of some kind it seems to me.

Many head gaskets use the same basic seals around water ports. Once the coolant damages the seals the sealing is compromised

JHZR2 · May 4, 2019

Originally Posted by Chris142

Many head gaskets use the same basic seals around water ports. Once the coolant damages the seals the sealing is compromised

Understand, but you specifically said water pump. So I was trying to link head gasket being compromised to water pump needing to be replaced...

clinebarger · May 4, 2019

Interesting....The author picked an engine that's so rare that any problems found with using Dexcool doesn't necessarily mean they will occur in other engines. He states "The head gasket is not compressed in the areas outside of the cylinder liners" What he doesn't state is.....The LT5 is a Open Deck design with Floating Sleeves/Liners, So the coolant is exposed to the Head Gasket around the Sleeves. The Gen II LT1 & LT4 used a Composite Head Gasket very similar to the LT5.....I never seen/experienced any failure that was related to Dexcool. But the Gen II SBC was a Closed Deck-Parent Bore cast iron block with Aluminum heads (Camaro/Corvette). Today....Composite Core Head Gaskets are obsolete, Even when I rebuild a Gen II engine, It gets MLS (Multi Layered Steel) HG's.

JHZR2 · May 5, 2019

Well, it is on a ZR-1 specialist site... so it's emphasizing that specific engine, if rare, because of the intent of the site... Level of exposure and block design aside, some coating either swelled, or it didn't... And due to dexcool/oat/lack of silicate, or not....

dlundblad · May 5, 2019

I've seen your threads in the past on how you've had such good luck with DexCool. Is that not the case anymore? Aren't you the original owner of your ZR2? It's a good way to know for sure that the system has gotten the correct coolant it's whole life. It seems that people tend to blame DC when in fact it's just that wrong coolants were mixed.. Yours is a good (and rare) example of that not being the case. I know GM updated their LIM gaskets for this engine. Could be for the same reasons in the posted link.

JHZR2 · May 5, 2019

Originally Posted by dlundblad

I've seen your threads in the past on how you've had such good luck with DexCool. Is that not the case anymore? Aren't you the original owner of your ZR2? It's a good way to know for sure that the system has gotten the correct coolant it's whole life. It seems that people tend to blame DC when in fact it's just that wrong coolants were mixed.. Yours is a good (and rare) example of that not being the case. I know GM updated their LIM gaskets for this engine. Could be for the same reasons in the posted link.

Why would you link one vehicle I own to a general discussion I've created, sourcing from a site oriented towards a high performance, niche engine? That's a big, assumptive stretch. I'm generally interested. Dexcool is the conversation in that document, but the culprit, if that paper is onto something, is a component in Dex... 2-EHA seems to get most blame. Interactions of OATs is merely of interest. If the opinions in that paper are onto something, and if materials in HGs can truly swell like that is more my interest. I'm having no issues with my S-10, which has a vastly different engine than a C4 ZR-1.

clinebarger · May 5, 2019

Originally Posted by JHZR2

Well, it is on a ZR-1 specialist site... so it's emphasizing that specific engine, if rare, because of the intent of the site... Level of exposure and block design aside, some coating either swelled, or it didn't... And due to dexcool/oat/lack of silicate, or not....

Sounds like he's blaming OAT......With such a small sample size, I have a hard time believing his assumptions. I've only heard 2-EHA as being a Plasticizer.....Even though plastic parts exposed to coolants without 2-EHA have issues as well. Ford was dead set against 2-EHA, And I've fixed a lot of Fords with leaky plastic cooling components.