Head Gasket Blown durning WOT, beware!

Benjamin Simon · #1 (**permalink**) 07-30-05, 03:55 PM

Some bad news... In my 99 STS I blew a HG. Perhaps it would have happened anyways, but I was doing a WOT excerise one day to clean our the carbon. Ever since then, (500 miles) I have been losing coolant. I could not find out where it was going. I took it to a mech and he did a hG test. The liquid turned yellow. I need a new HG.

I had one quote for 2 grand. Does anyone know a good price for this to be done?

My advice is be careful when doing WOT. I did the WOT per the suggestion of the Cadillac Technical Archive. I am not sure if this was the straw that broke the camel's back, but anyone with a high milliage caddy needs to be aware.

tttjump · #2 (**permalink**) 07-30-05, 05:47 PM

Well, the next time you need to pass someone or climb a steep grade are you suggesting that high mileage caddies shouldn't mashed the gas pedal to the floor? Timing is everything I dont think that the WOT cause your situation or is linked to it at all, just my two cents.

Eldyfig · #3 (**permalink**) 07-30-05, 08:09 PM

I feel bad for your caddy. It was probably coming. I don't believe the WOT is the cause, just the last straw. How many miles do you have on a 99?

Mark Bunds · #4 (**permalink**) 07-30-05, 08:54 PM

That's a shame, sorry it happened to you.

It would have happened anyway though, even if you were babying it along like grandma, sooner or later. Head gaskets either blow, or they don't, mainly depending on the flatness of the surfaces that clamp them, but sometimes because of minor flaws that can surface long after the engine has gone beyond it's warranty. Some Northstars have passed 200k with no problems, Most are doing fine with over 100k, and some have blown within days of leaving the showroom floor. It happens, sorry it was you.

zonie77 · #5 (**permalink**) 07-30-05, 09:00 PM

I think it was ready to blow anyway. Most of them go from corrosion. The WOT may have shown it but it was like turning on a lamp and having the bulb blow. It was close and that's when it showed up

Benjamin Simon · #6 (**permalink**) 07-30-05, 09:43 PM

I would certainly agree, doing a WOT could not be the only colprate. I am sure it was going to happen anyways. I am just concerned the way in which i do the WOT could have pushed it over the edge faster. I am always hotroding my N*, but when I read on the Cadillac Technical Archive I started doing the in a more "intense" fashion. I would but the car into 2nd at 55 MPH, floor it up to 6100 RPM (right before the computer would force it to switch) and I would let the enging slow itself down and do it again. I dont really consider passing someone a WOT, or atleast one for long.

I understand my Caddy has 115K, and shit like this will happen. Does anyone know how much this might cost? I have an extended warrenty, but I am just curious.

When this is being done, should I have anything else that is easy to get to replaced? What about some performance mods!

Mark Bunds · #7 (**permalink**) 07-30-05, 10:38 PM

Quote:

Originally Posted by Benjamin Simon

When this is being done, should I have anything else that is easy to get to replaced? What about some performance mods!

If you get the heads rebuilt by the right shop, you could have them ported and polished which is one of the standard things people do to improve flow.

If you do something radical, like having the heads milled, you can increase your compression ratio for more hp, BUT you will have to run higher octane fuel to prevent detonation. Only have this done by a shop with Northstar experience. It will also cost a lot of money.

Be sure that any shop you choose uses thread inserts (time serts) in the block before reassembly because the Northstar aluminum block has a bad reputation for head bolt thread damage when the head bolts are removed and re-torqued. This is the part that costs so much in a N* head gasket job, $2G is in the ballpark.

And also be sure that the shop uses NEW OEM bolts for reassembly; you cannot reuse the old ones; they are the "torque to yeild" type and will have lost their temper once they are removed.

zonie77 · #8 (**permalink**) 07-31-05, 03:47 AM

The heads are very good as is. I don't think there is much to be gained by porting. Not enough to justify the cost. The engine is well designed and there isn't much easy horsepower to gain.

Look at the head gasket thread in the tech tips section and you'll have an idea why it costs so much. $2K is cheap.

Make sure it gets timeserted. All 20 holes, not just any stripped ones. This will add significant cost but it's worth it.

niteryder · #9 (**permalink**) 08-01-05, 03:30 AM

I am new to this site - please fill me in on what WOT is?

**Jesda** · #10 (**permalink**) 08-01-05, 06:09 AM

Wide open throttle, when you have the gas pedal fully pressed to the floor and youre accelerating with all your might all the way to the redline (highest rpms).

Mr. Select · #11 (**permalink**) 08-01-05, 06:16 AM

WOT...Wide Open Throttle..

Kev · #12 (**permalink**) 08-01-05, 06:18 AM

Quote:

Originally Posted by niteryder

I am new to this site - please fill me in on what WOT is?

Welcome niteryder.
WOT=Wide Open Throttle.
This is recommended for most engines avery now and then to clear out corbon buildup in the cylinders. It is especially important in the higher performance Northstar engines.

Quote:

Originally Posted by Mark Bunds

If you get the heads rebuilt by the right shop, you could have them ported and polished which is one of the standard things people do to improve flow.

If you do something radical, like having the heads milled, you can increase your compression ratio for more hp, BUT you will have to run higher octane fuel to prevent detonation. Only have this done by a shop with Northstar experience. It will also cost a lot of money.

Be sure that any shop you choose uses thread inserts (time serts) in the block before reassembly because the Northstar aluminum block has a bad reputation for head bolt thread damage when the head bolts are removed and re-torqued. This is the part that costs so much in a N* head gasket job, $2G is in the ballpark.

And also be sure that the shop uses NEW OEM bolts for reassembly; you cannot reuse the old ones; they are the "torque to yeild" type and will have lost their temper once they are removed.

I wouldn't rebuild the heads unless I planned to install fresh rings and main bearings. Rebuilding the heads will put added strain on the existing rings and bearings.

I would merely have the heads cleaned and surfaced (to ensure no warpage), maybe have new seals installed on the valve stems but no more.

Just my two cents.

danbuc · #13 (**permalink**) 08-01-05, 10:33 AM

The exhaust ports on the heads could use a little porting and polishing, but I would only consider this if you were going to extrude hone the exhaust manifolds, and install a low backpressure exhaust system.

As people said before, your headgasket failure has nothing to do with the WOT maneuver. As an example, I believe there is also someone here with a 2000 STS with roughly 65k? whos unfortunetly had a head gasket go. There is also someone up in Canada? with a Deville that got over 300k? miles without a single problem. Unfortunetly with these car it seems to be hit or miss, whether or not you'll have a problem. The nice thing toknow, is that after being timeserted, few if any ever have another problem again. Good Luck with the repair, hope evrything works out.

**Ranger** · #14 (**permalink**) 08-01-05, 01:45 PM

Quote:

Originally Posted by niteryder

I am new to this site - please fill me in on what WOT is?

From the Archives
Occasional Full-Throttle Acceleration Is Good For Your Engine

niteryder · #15 (**permalink**) 08-01-05, 06:25 PM

Thanks to those who enlightened me on WOT! I have a 94 STS w/ 650,000K (Canada) or 400K miles. Have done the HG and helicoiled the head bolts at 250K mi. No problems since - still original rings, valve, bearings.... Recently took a defensive driving course where "WOT" was employed several times during maneuvers. No problems - altho I admit to some apprehension at the time.