351W Coolant leak

[timsullivan]

My 408, which is based upon a late model 351W roller block seems to have a very small water leak at the intersection of the timing cover, engine block and oil pan as I've noticed moisture there.

I can't seem to pinpoint the leak exactly though and at first thought I had a seeping freeze plug. When I bring the car in and park it after running hard I'll get a teaspoon size drip running down the right front corner of my oil pan.

The problem is I can't seem to pinpoint the leak location exactly because the seepage seems to get blown around the lower right front of the engine. I tried pressure testing the cooling system and it would hold about 20 pounds for 30 minutes and no obvious leaking!

Any ideas?

[madmaxx]

probably between water pump and backing plate. it is a stupid design, water pump has a backing plate. so two gaskets one between water pump and backing plate and one between backing plate and timng cover. You cannot tighten the 4 screws holding the backing plate on once pump installed on car. so it may very well be leaking there.

[Xavier]

I had the exact same thing happen to me with my motor, turned out to be the inlet water neck from the manifold. It would only do it when really hot, and it would drip, slowly like yours, so it would appear like it would come from every where else. There are a lot of comments on the Chrome water necks that are out there using substandard finishing or steel for the application. Once the water neck heats up (or even not heated) the base becomes (or is) slightly dished where mounted to the manifold. Once cools, it seals tight, once hot, it slightly becomes unsealed. Most of these beautiful water necks, are Chinese, and have this issue.

I swapped mine out for a two-piece Stainless Steel billet water neck (entirely overkill, but a work of art) and never had the problem again. I since then replaced it with a FE style surge tank, so if you want it, make me an offer. It is absolutely solid, and is worth every penny. It is a shame something so nice is just sitting on my work bench.

[Rick Parker]

Every time I see a thread regarding minor coolant leaks I recommend the following:

[quote]--------------------------------------------------------------------------------

GM is still using the pellets on the LS engines today. When you buy a new LS3 crate engine from the general and take off the water pump you will find two round "stop leak" tablets in the block.

The pellets look like very fine, small granulars that have been pressed to form a tablet. My guess is that out of all the stop leak products, these items will cause the LEAST amount of potential stoppage to items like heater cores and cooling passages. They can still be purchased at a GM dealer at the parts counter. Safe for Aluminum applications.[quote]

At many GM stores it is common practice to put 2 of these in the cooling system after removing the manifold or heads for any work. I eliminates small leaks throughout the cooling system without compromising the radiator. I've seen it done many times. This saves the techs a lot of headaches for comebacks, and it's not messy at all. They are about 1 " in diameter and about 3/4" thick.

http://www.parts123.com/parts123/yb....0h~Z5Z5Z5HAWMC

[BDR879]

I'm running a 428FE and am just starting to break it in. My engine builder suggested I go to Wal Mart and get a product called "Bars Leaks" (cost about $3). He had me take a teaspoon of the pellets from the can and add it to the overflow tank along with 1/2 the liquid in the bottle. He said that it was a good preventative measure against any nuisance leaks.

[madmaxx]

I am 100% proponent of the adding Bars leak etc as a preventative measure. Cost a couple bucks, I agree dump a bottle in and see if that solves your leak. It is also a good preventative measure as others have indicated for the bolts that going into cooling passages to seal the threads.

[timsullivan]

Okay guys, thanks for the tips and advice. I'll give the prodcts a try.

[RedBarchetta]

Originally Posted by timsullivan

When I bring the car in and park it after running hard I'll get a teaspoon size drip running down the right front corner of my oil pan.

Tim, I'm willing to bet that you have some seepage from the water neck where the expansion tank bolts to the intake. Happens more times than you'd think. On a cold motor, or after idling for less than 30 seconds from a cold start, take a dry finger and reach in from the top and feel under that joint at the intake manifold. You will probably detect dampness. If so, disassemble and clean both flanges really well, then hit it with a fresh gasket and Permatex Ultra Black. After tightening, let it set for 24 hours before refilling the tank.

There are other procedures posted here that will give you clues on how to bleed the system (meaning that curing one problem can create another...a steam pocket that causes fluctuations in engine temp). The best way to burp the system is to loosen the water temp sender and bleed air from there.

I'd come down and help you but I'm out of town this week and next. Send me an e-mail if you have questions, as I don't post here much any more and I wanted to help you out.

-Dean

[vector1]

weep hole from the water pump?

[timsullivan]

Thanks Dean, I'll give it a try.

-Tim

[timsullivan]

Bought a small 10 oz. container of "Bars Leaks Radiator Stop Leak" and threw it in the expansion tank and took the Cobra out for a nice, long, hot run. Came back home and let it heat sink in the garage for a few minutes. Looked under the car and the small leak that used to dribble out on the ground was gone! Couldn't believe it so the next day I wiped down the front corner of the motor and oil pan area, removing all of the previous coolant drips and took it out for another long, hot run in our recent 100 degree weather in SoCal. Came back home, let her heat sink for 15 minutes and looked under the car and all around the lower right front corner of the motor and guess what? LEAK BEGONE!!!!

I would have swore that "Stop Leak" wouldn't stop a damn thing but it sure solved my problem once and for all! The wonders of modern science?

[jwd]

Originally Posted by timsullivan

I would have swore that "Stop Leak" wouldn't stop a damn thing but it sure solved my problem once and for all! The wonders of modern science?

EVERY car manufacturer uses a stop leak product in their new cars. Most,if not all, crate motors will have stop leak pellets installed in the water outlet as well.

[tcrist]

It might sound strange but before there was anything like Bars leaks or those little pellets like GM sells, my dad used to use "sodium silicate" (egg preservative).

If he had a small hole in his radiator that produced even a small steady stream of water, he would pour in about 1/2 gallon, just set there with the car running and you could watch the leak stop. He would leave it in for about 1 hour of run time, flush it out and refill with water.

Ok, I am talking about the 50'S and 60's here so don't laugh too hard. I would almost bet that some of the old timers around here have heard of it also.

There are more effective products on the market now. Just bringing up some old remedies that I learned from my dad.

[Rick Parker]

I have even heard of white Rice being used.

[sllib]

We used black pepper back in the 60's. It swells up and gets soft in hot water, then hardens when it hits the cool air at the leak.
Bill Stradtner

[Rick Parker]

Good idea, maybe Chili pepper for high compression, big cams?

[Z-linkCobra]

Originally Posted by sllib

We used black pepper back in the 60's. It swells up and gets soft in hot water, then hardens when it hits the cool air at the leak.
Bill Stradtner

I have used black pepper in the past....works pretty well...doesnt last as long though.

[RedBarchetta]

Are some of you plugging leaks or making soup?!?

[sllib]

I got stranded more than once by the crap I used to drive back then. Soup would have been nice!!!

[PANAVIA]

My wifes grandfather used to regail us of stories of oatmeal being used in a similar way.

" every time we drove that truck {a 1935 ford ) we'ed get hungry"

Steve