Hey yall,
I need your help.......

So for all of you that have followed my thread you know we "finished" the build last week and finally got to drive our truck. Well, about 2 days after we got her on the road she started to leak coolant on the driveway. I thought it was a loose hose or something because the engine only has 1700 mile on it since rebuild.

The leak started on the passengers side at the back of the head near where the intake meets the head. We found this by using uv dye. The leak would start when the thermostat opened and would stop when the engine would reach temp. I thought the head may have needed to be re torqued so I just checked the bolts and found a couple that were a little under the 105 foot lbs needed. I didnt do a full re torque by draining the coolant and loosing the bolts before re tightening them - I just checked if they were loose. After this the leak slowed down by half. I thought maybe the intake may be loose too so I re torqued it too.

After the re torque on the intake, then drivers side started leaking bad - one drip a second or so!! It was coming from the back of the head near the intake too! Also, I after that I was getting coolant in the exhaust too.

I figured that intake must be the problem until I realized the intake doesnt have coolant running through it.

Here is my dilemma.... Could it be possible to have 2 bad head gaskets after a rebuild from a reputable shop or does it just need a proper re torque? I would hate to pull the heads on a new engine just to find out they needed a re torque (that I plan on doing in the morning). But if I do the re torque and put everything back together and it still leaks Ill be quite upset.

Any advice? Anyone experience this before?
Thanks

 

Good head gaskets, torqued-down in stages, shouldn't need to be re-torqued.

Even though the coolant doesn't go through the intake, the coolant still gets to the "face" of the intake. Sounds to me like the intake manifold gasket. On mine, the instructions said to rtv around the coolant openings. I'd check that first, after all, you have to pull the intake to pull the heads.

The reason that it leaks more as it builds temperature is because the pressure is also building. It quits leaking when the thermostat opens because the pressure drops

I see you have an electrical temperature sender in the thermostat housing, and a mechanical sender in the water pump. Neither will give you a good "internal" reading. What's the brass fitting in the front upper left of the block? That's the best place for your mechanical sender

 

Did you assemble the engine or did the rebuilder?? If the rebuilder did, I would put the ball in their court and see how they want to handle it!!!

 

Do not loosen the bolts, just retorque them.

 

Thanks for the reply. So I thought the coolant goes to the face of the intake too but I cant find any place where coolant comes out of the top of the heads. The holes in the front and back look like they are hearing the intake for EGR reasons. I hope its the intake, that would be easy!

The engine was purchased by the previous owner 2 years ago and he put 1500 miles on before he couldn't afford to fix the other parts. We bought it and started the rebuild 1.5 years ago.
Ive called the engine shop but they are 2 hours away. They cant imagine what it may be but have been helpful. I dont want to pull the engine and take it up there if I dont have to.

 

Huh.. Ok.. I was told to drain the coolant, crack the bolts loose then tighten in order. First time having to do this.

 

From what its worth. I have been building engines for over 35 years and based on what you have already posted I'd pull the intake and replace those gaskets. First I'd loosen all the rockers and double check torque on all the cylinder head bolts without loosening any of those. But! If the truck were mine I'd pull the engine and reseal it just for piece of mind. At minimum I'd change the head gaskets with the engine still in the truck.

 

Thanks for the reply...
I have the intake out now and the valve covers off to check the head bolts. I just didnt want to change the head gaskets if I didn't need to. Strange that Id get leaks from both sides in the same place.

 

Well, I re torqued the heads and put everything back together and so far no leaks. The head bolts seemed a little loose. I marked all of them before I torqued them and all but 1 went about 1/8 to 1/4 inch past the mark.

 

Good to hear. It wouldn't hurt a thing to put a little vial of that powdered copper seal in your cooling system. The powder will not hurt a thing and will fill any small little gaps or imperfections in the gaskets. Some of the older ranch trucks we work on develop some small leaks here and there in this West Texas heat. Most often it takes care of it.

 

His engine is a 335 Series it has a Dry intake no coolant in the intake.

This is a head gasket issue.

 

Sounds like who ever did the head gaskets needs their torque wrench needs re-calibrated or they missed the final torquing or going over them once again after torquing.
Be sure to change your oil also as it may have been contaminated.

 

You are right!!!

Was in the basement a bit ago (10-20-16) and was just piddling about and decided to pull out my welder and dig those 400 heads out from under the steps ... dust and all. Hadn't looked at them since the mid '90s. Noticed black soot in the holes, used a dowel rod and sure enough, straight to the thermactor passage way on the exhaust side above exhaust ports. One goes straight across, the other at an angle to miss head bolts and stuff.

I took his pic and cropped it, lightened it up, circled the holes which don't appear on AM heads usually. My extra set of OEM 400 heads laying under my stairs have the same holes.



Then came here to correct my post so no one is lead astray and found yours .....

 

Those holes are the thermatic passage for the AIR injection in to the exhaust port. If you blow in to that hole on your heads you will see that it comes out in the exhaust ports. In some applications (no smog pump) they are blocked off with an expansion plug.

 

Yep! .....