I can't belive my cylinders

[cngmike]

I missed going out to the Thunder on Sunday with a blown head gasket on my 94 Caravan. I finally got both heads off today only to find very clear cross hash marks on the cylinder walls. The engine has about 110,000 miles no ridges grooves just those cross hash. I've never seen any thing like this, just how long will this engine last? The guys from Super Shuttle always told me that they would feel cheated if they didn't get at lest 300,000 miles. They would retire vans because the van was dyeing around the engine.

[Curtis]

Re: I can't belive my cylinders

Sorry to hear about the engine. We hate to see anyone miss the Cruise-In, even more so for mechanical reasons. Not to worry though, we'll do it again next year.

Honda says they expect 300k out of a GX. I've gotten 400k out of mulitple gasoline Honda's. I would expect that 500k isn't unreasonable... maybe lots more. It would be the first Honda I owned that fell apart around the motor. American made cng's will do just that, only faster. 300k would be a fair guess. It's the rest of the mechanical items, and interior that will go first.

[afvman]

Re: I can't belive my cylinders

Hello all,

Any of us gear heads that have been inside a CNG engine have had the same 'WOW' experience...and for good reason.

The most obvious is the lower carbon content on CNG, ch4 compared to gasoline at c8h18! Less obvious is the higher octane (125-130 vs. 87). Most relate this to anti-knock, but it also translates to a slower flame propagation rate. CNG has a longer, slower power stroke that results in less banging on the bottom end main and rod bearings, thus longer engine life.

CNG rules!

afvman/Bill

[cnghal]

Re: I can't belive my cylinders

Mike,
The Supershuttle guys are spoiled, short of spark plugs blowing out (usually cylinder#3), thier vans do fall apart around the engine. I have had 10 of thier vans. 2 had new engines after 300k (probably run out of oil), most 400-450k and still running strong. I have one in my yard I use for parts that has 562K on it when it was retired. Tailpipe is still clean inside.
I plan on rebuilding the engine once I get my engine dyno setup. I'm dying to see what the inside of this thing looks like.

[josch]

Re: I can't believe my cylinders

Sorry to hear about your head gaskets.

Yeah, so now that you have new head gaskets, you'll have to be sure to change your coolant at least every 2 years (if it's the green stuff), so the pH doesn't go acidic and then you wont have to change those gaskets again when it hits 220k

By the way, you can buy special coolant test strips for dipping, to test your pH once in a while. This is what I always used when I worked in the automotive industry: http://www.cooltrak.com/

Because once it goes acidic, it doesn't take long for it to eat out your fiber gasketry. Every head gasket job I ever did the pH was way off.

Just food for thought. I don't mean it in a negative way. Head gasket problems for the most part, are preventable. Think of this as constructive criticism (since I provided a URL)

By the way, make sure that if your van uses torque-to-yield head bolts, make sure you replace them. They are only good once. Then they loose their spring.

[cngmike]

Re: I can't belive my cylinders

The most important thing is to teach the son what the temp gaugee is for. The cooling fan went bad and he kept driving. While I'm at it I'm also having the the injectors cleaned and checked.

[cnghal]

Re: I can't belive my cylinders

Mike,
I ended up putting 2-12" electric fans in my 94 Caravan when mine went.
One two speed run by the stock relays and one thermistat controlled at 195°F. Ended up being cheaper than a $300 stock replacement. Plus we need as much cooling as possible here in the desert. Mine's got 250k on it and no smoke, leaks or engine problems.