Miles for new valves

EASYTRADER · Nov 2, 2012

I have 790k miles on my hino, it has started having overheatin issues. It was actin like a head gasket. To make a lon story short we pulled the head and tye gasket looked fine. They sent the head out to xray for cracks and it is fine. However the head shop said about half the valves failed to hold pressure so they did a full valve replacement. The dealer tells me that they suspect the head leak was in the injector cups, which they replace anyway when they pull the head. But they cant prove it,

So im puzzled why my valves would be shot but the rest of the engine is fine? Is that normal?

Also how long do valves last normaly.

I dont doubt tue valves were bad, there was alot of oil in the blow by.

Also im dubious anout the injector cups leak, is that a legit explanation for headgasket style over heating?

Thanks for your help.

Also my bill is up t0 6k

Refer Hauler · Nov 2, 2012

Have always been told to check the valves on a new engine or head @ 50K miles then have the valves checked and adjusted every 250K miles. I have followed this advice and have never had a valve issue. With the newer electronicaly controlled engines you may be able to exceed the mileage suggestion above.

davekc · Nov 2, 2012

If the injector cups are bad you likely would have deisel mixed into your coolant.

Dynamite 1 · Nov 2, 2012

did they resurface the head when they did the repair ?

EASYTRADER · Nov 2, 2012

Dave,

The dealer told me my coolant tested positive for exhaust contamination. But I don't know how they tested for it.

I don't believe they resurfaced the head, but the people who xrayed and pressure tested it said the head was fine but the valves were leaky.

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paullud · Nov 2, 2012

Exhaust contamination in your coolant usually means a cracked head or bad head gasket. If it isn't already put back together you might want to consider having the head magnafluxed. Hopefully it is just the head gasket so you can just get a new gasket, flush your coolant system and get back out on the road.

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moose · Nov 2, 2012

send you story to Julie from filtration solutions : [email protected]
she is an expert and sees many issues like this every week.

Dynamite 1 · Nov 3, 2012

xray and pressure testing has nothing to do with making sure the mating surface of the head is true. this can cause premature failure of head gaskets. it amazes me how most shops never bother to check or do this while head work is being done.

Mdbtyhtr · Nov 3, 2012

They should have Magnafluxed the head with all of the valves out, i have also seem heads that pressure tested fine, cold, but showed cracks when the head was heated. Premature valve wear is attributed to poor valve adjustment. Valves only cool when they are seated. If they are too tight, they are not seated, if they are too loose they don't stay open for enough duration to properly scavenge the cylinder. Valve seat pressure can also cause leakage if the static pressure of the springs are too weak.
Scott

EASYTRADER · Nov 14, 2012

Well, I got the truck back.

6800 bucks mosty labor. I road tested it on the Cajon pass, that's the big hill between ONtario Ca and barstow on the 15. The temperature held fine, and the truck ran up the hill only dropping 5 mph. Which is way better than it was before.

It sounds better now than it did when it was new.

So I was jsut surpised the valves would be shot while the rest of the engine looks great.

I have the valves adjusted once a year, maybe sombody screwed up the adjustment.

I was totaly surprised to see that there was NO visible wear on the Camshaft. Only one lobe even had a wear shadow. When I saw it out of the truck I thought I was looking a new part. Anyway, that's using Amsoil and a bypass filter.

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davekc · Nov 14, 2012

Truck'in ain't cheap.

jt1980a · Nov 16, 2012

Is you Hino between an 03 and 05 model year? There were manufacturing issues with heads through these years due to manufacturing being jobbed out to the cheapest bidder. Casting imperfectins caused hairline cracks that did what you are saying. Causing valves to go bad from the heat and carbon buildup.