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Another overheating Q from me, help before I pull the 406!

rjfguitar

rjfguitar

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OK, I can see a trail of coolant running down the head behind number 8 cylinder but it looks almost like it is coming from the corner of the intake manifold, thats not possible right? Because the coolant ports are more towards the middle right? /forums/images/graemlins/thinking.gif I figured it was the passenger side head gasket from seeing the water but I notice that I am getting a small trail of white smoke out of the driver side exhaust for about 10 or 15 mins. after start up, opposite side to where I see coolant running down the head. /forums/images/graemlins/confused.gif /forums/images/graemlins/dunno.gif My 406 has been wanting to run warm for a long time but has gotten worse fast in the last month or so. I checked the water this morning and it was low so I am definantly burning or losing some coolant somewhere but the oil and water have not mixed yet. I have replaced everything in my cooling system except for my water pump but it seems fine and it's brand new anyway. I have narrowed it down that it has to be something internally in the motor with either the intake manifold, the head, or head gasket(s). A mechanic that works on our semis at times is coming to help me do something with it but I need to make a decision if it is just one head gasket, leave the motor in, and replace it. Or if it is both gaskets and I would be money ahead to just pay him to help me pull the motor out and rebuild the top end. /forums/images/graemlins/doah.gif What should I do? /forums/images/graemlins/dunno.gif What are some problems you guys have had with overheating issues, head gasket issues, anything that sounds related to my problem? Thanks.
 
The water passages in the intake are on the ends. It sounds like a head gasket (hopefully not a crack). A good place to start would be with a leak down check. Definitely check the oil for evidence of water.

As far as rebuilding the top end - theres no reason to pull the motor. It can all be done easily enough with the engine in the truck.

Good luck!
 
is it a DD? or off road rig? if you dont need it everyday i'd pull the manifold do some cleaning and see from there, ususally if it has been leaking for a while you can see where the gasket failed. if there are no "traces" from the intake doing the rest of the top end is really no big deal... pull the heads off have them checked for cracks and straightness, then may as well do a valve job and make sure things are spotlessly clean and put er back together. p.s. dont use the end rail pieces that come in the intake manifold gasket set just use rtv. good luck
 
sometimes you can get lucky and put some sodium silicate (stop leak) in the radiator and it will fix the leaking head gasket. Worked on my old 78.
 
I think you just need to bite the bullet and replace the head gaskets. /forums/images/graemlins/deal.gif
 
I would do as mentioned before, since you have to remove the intake before the heads anyways, any leaks will be obvious. Just start with that, especially if you have an aluminum intake manifold, ya'll know those corrode after awhile anyways, If no leaks, then continue downward with the heads. Depending on how many miles are on the engine should be the determining factor on a rebuild or not.

Just my thoughts /forums/images/graemlins/waytogo.gif
 
I second the idea of checking your oil for coolant.
Don't overlook the freeze plugs in the block... Those could be leaking.

Sounds like either the intake manifold or head gasket. /forums/images/graemlins/thinking.gif
 
Well, you guys reasured me about what I was thinking, either the head gasket or intake. /forums/images/graemlins/thinking.gif.

As for the questions, it has about 10,000 miles on the motor and it's built up pretty good with the usuall upgrades like cam, compression, flat tops, etc. I was just thinking it would be easier to replace all the top end gaskets with the motor out. My K5 is awfully tall. There is no water in the oil but it is using a little bit of coolant. Oh, and my K5 is a DD so it can't be down for long. /forums/images/graemlins/doah.gif I picked up 2 new head gaskets, intake gaskets,valve cover gaskets, and RTV for the ends of the intake. Our mechanic that handles some of our semi truck road calls is coming in the morning to replace everything for me. I would do it but am just too busy getting all my rice planted (320 acres) and I feel better letting a proffessional do it. (because I guess I did something wrong when I assembled it)
/forums/images/graemlins/dunno.gifAnother question. Like I said the motor only has 10K on it. What would have caused the head gaskets to fail? I built the motor along with my soon to be father-in-law and We used fel pro gaskets. Same for the intake...what would cause it to fail? And most importantly what should I do to keep it from happening again?
 
I bet its the intake. At work today we just did an intake manifold reseal on a '97 Chevy that was leaking like all hell broke loose from the back of the engine. Make sure you do a block test before you pull the heads off. That is a sure fire way of knowing if a head gasket is bad because it will detect exhaust gases in the coolant.
 
[ QUOTE ]
I bet its the intake. At work today we just did an intake manifold reseal on a '97 Chevy that was leaking like all hell broke loose from the back of the engine. Make sure you do a block test before you pull the heads off. That is a sure fire way of knowing if a head gasket is bad because it will detect exhaust gases in the coolant.

[/ QUOTE ]
What were the symtoms of that 97' besides the leak? Any overheating issues?
 
i know you man,i know how you get on that skinny. thats a rockin motor!!!i remember my 383,and i got on it,and on it,and on it,until it dogged ass .I might treat her kinder this time,because i paid for it in the longrun.I wish ya well,but mabey SLOOOW DOOWWN a little this time.*just my thought* jake /forums/images/graemlins/thumb.gif
 
how is your timing?
that can cause a higher temp as well.

i would pull both heads and replace the gaskits if needed. if not needed then go from there. check the heads for warpage. check the block as well.
Grant
 
Same thing on my 75, had coolant leak and was running hot, I could not visably see the coolant as it was being condensed or evaperating do to heat on the back of the block.

So I sit there and shure as Brittany Spear's boobies are fake, I see a trickle on the back of the intake. Some times those cheezy rubber gaskets move around on ya when you install the intake, have just enough to get you buy and then "bam" out of now where like Sunny Bono hit that tree, it will leak.


I got some revenge with a heathy amount of rtv after pulling the intake and did not reuse the crappy rubber dohicky...

sometimes even the best rubber can let some get by /forums/images/graemlins/histerical.gif

same issue on my neghibors 99 suburban, and my dads 68 camaro, all solved the same way /forums/images/graemlins/tongue.gif

-shawn /forums/images/graemlins/usaflag.gif
 
Once again, a solid piece of advice from a pro (Z3PR). /forums/images/graemlins/rolleyes.gif

I would look at the possibility of the intake manifold seals leaking, before pulling the heads. As previously mentioned, sometimes the manifold gaskets tend to leak, fairly easily. The aluminum expands at a different rate than the cast iron block and heads. If your head and block mating surfaces were flat when assembling the engine, and you torqued the head bolts correctly, I doubt that a head gasket decided to fail.

Good luck, you'll figure it out. /forums/images/graemlins/waytogo.gif
 
[ QUOTE ]
My K5 is awfully tall.

[/ QUOTE ]
remove the inner fenders, do the heads, then put the inner fenders back on.
PLENTY of room like that.
GM should have put DZUS fasteners in for them i say.
Grant
 
A leak on the outside would have to be one nasty crack on the head.
Sounds like an intake gasget.
I would pressureize the coolant system and do a combustion leak test before I started tossing parts at it.
Those blocks are notorious for overheating in stock form.
Start pumping up the power and it can get worse.
Are the heads 400 heads with the steam holes?
 
You used factore 400 heads with the steam holes already, correct? A street motor needs the steam holes.

I drilled the steam holes myself on the S/R Torquers, and did a crappy job /forums/images/graemlins/dunno.gif /forums/images/graemlins/dunno.gif The head gasket failed, and I was blowing anti-freeze out the tail pipe. The cure was letting the machine shop fix my drill job and reassembly.

My 400 did not run warm, but I'll bet the 4 core rad and 180* thermostat had something to do with that.

Do the tests mentioned above, and start with the intake.

Did the warm engine start before or after the trip to the dyno?
 
:UPDATE:
Well guys the motor is down to a short block and the rest is scattered around in my garage this evening. /forums/images/graemlins/rotfl.gif We pressurized the cooling system and it started to drop pretty fast, had a small leak in the thermo stat housing and at the back of the intake. We also figure that there was a little coolant seeping between the head and block near #8. We got the intake off to reveal that the gaskets were in decent shape and that it was leaking just a little but not enough to cause a problem. Then we decided to pull both heads, got them off to reveal both head gaskets in good shape. /forums/images/graemlins/doah.gif We are pondering if their could be a crack(s) in the head. I am going to pick up a new hi flow thermo stat in the morning and will probably put it back together unless I decide to get the heads magnafluxed. I don't really know what do to right now or why it wants to run warm. /forums/images/graemlins/dunno.gif /forums/images/graemlins/thinking.gif I have a brand new 4 core rad. and 180 stat and I am going to put it all back together, mount a big ass electric puller fan, and run it. /forums/images/graemlins/thinking.gif

Are 400's really that hard to keep cool? Can they be kept around 190 degrees with A/C and warmer weather? Am I just wanting too much with wanting it to stay at 180-195?
Brand new 4 core + high flow 160 stat + hi performance pump
= a cool 400 right? I hope so. /forums/images/graemlins/doah.gif /forums/images/graemlins/dunno.gif
 
You dont want the coolant to flow too fast or you'll have just as bad as over-heating problem. Try running a 195 t-stat instead of a high-flo 160. T-stat's are easy to change so dont be afraid to experiment with those. If you think the head is cracked send it out and get it magged. Thats the only way to be sure, that way you know everything is right and dont forget to straight edge the block and head.
 
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