Coolant Leak

[DipStick82]

Howdy fellas,

So I seem to have a coolant leak in my 71' C10 Custom with a Good Wrench 350. I've been noticing leaks on the ground and pooling in the pan below my radiator--more leaking after longer periods of driving and overnight after driving home from work--at time it will nearly deplete the radiator reservoir of coolant. After a recent depletion I filled the radiator only to find a large pool on the ground after the first drive.

The next day or so I found coolant on the top of the block (picture attached). I am hoping this was just a hose leak and not a gasket. Is it possible that the gasket show in the photo is leaking?

I'd like to start trouble shooting this but don't know exactly where to start...

Any insights are much appreciated.

Thanks!
Kelley

[NoNeck]

I can't tell a lot from the photo, but it does look like you have coolant near the thermostat housing. It looks like either the intake manifold mounting surface at the housing has pitted or excess silicone.

To fix the pitting I would remove the thermostat housing and thermostat then cram a shop rag in the opening. Wrap 80 grit sandpaper around a paint stick or something flat. Remove as much of the pitting as you can while keeping the sandpaper very flat.

If it is just excess silicone, I would clean both the thermostat housing and manifold gasket surfaces really well. You might install a new thermostat in there while you have the housing off. Then pick up a quality gasket to finish the job.

The gasket in the photo is like the one I have used in the past. Maybe overkill, but great insurance against a failure at 1:00 in the morning. Here are the specs:

Fel-Pro
Manufacturer's Part Number: 2202

Oh, one more thing... I would replace the upper radiator hose, too. It appears to be "ballooning" pretty bad in the photo. Just my .02¢

POP

[DipStick82]

Thanks! NoNeck. What would cause the hose to balloon? It is a new hose. I don't want to pull the whole thermostate housing off it it just the hose leaking...

[firedemon]

autozone or any of those that will loan you tools will have a coolant system tester its a little air pump connected to a cap for the radiator pump it to about 10 pounds and start looking for leaks should be fairly obvious once its presurized

[87Skier]

Originally Posted by DipStick82

Thanks! NoNeck. What would cause the hose to balloon? It is a new hose. I don't want to pull the whole thermostate housing off it it just the hose leaking...

If you haven't changed your thermostat in a while (2 years or 20-30,000 miles) I would pull it anyway. It really is just the two bolts on top.

I've had similar issues to yours. Sometimes, tightening up the bolts and hose clamps a little, and I do mean a little, will stop the leaking.

[DipStick82]

Thanks! Not sure I have an autozone, but will try and find the tool to pressurize the radiator and coolant to find the leak. The thermostat would explain the oil around the housing but I feel I have a second leak closer to the radiator that is getting the coolant on the gound; it pools to the left or right depending on level of ground where it is parked.

If the thermostat housing is leaking: am I doing any damage by driving the truck in the meantime?

Thanks!

[firedemon]

any coolant leak isn't good overheating can lead to head gasket problems

[tdangle]

Wanted to share an experience I had years ago with a 454 in a 88 chevy truck. It would do the same thing leak a little when sitting around the thermostat housing. When warm it never leaked. after replacing the gasket a couple of times (always cleaning up the surface prior to the gasket installation) I finally replaced the housing. No more leak. BTW the truck was less than a year old when this happened.

I came to the conclusion that the metal would cool and shrink just enough to cause a leak at the gasket. When I started it up in the morning I could see a small leak (just a drip or two) until it warmed up and then no leak.

Good luck.

[firedemon]

ive seen that with mr gasket chrome housing covers

[hamjet]

By the photo, it looks like its just a loose hose clamp or bad hose..

[cleszkie]

Worn out water pump leaking through tell-tale weep hole? Hole in the radiator core? Leak from the heater core hose next to the thermostat housing on the intake manifold?

[DipStick82]

Where is the tell-tale weep hole?

[leftybass209]

You have a significant amount of fluid and issues above the water pump, you should work methodically top down, 1 thing at a time. You KNOW there's a leak above the pump, you do not know there's a water pump leak yet.

I would take some rags and a leaf blower and dry everything off first as well. Then WATCH everything and don't leave the truck unattended. The leak tester is great to induce a leak, but eyes on when and where the problem is occurring gives you experience. Inducing a cold leak may not cure all the issues.

[DipStick82]

So Lefty, you are suggesting that after I clean and dry everything, that I run the engine and watch for a leak as opposed to pressurizing the system cold; correct? Any possible damage being done to engine in this method (assuming my system has coolant in it).

Thanks!

[slikside]

I think that's exactly what he means.

As long as you keep the fluid level up, there shouldn't be any damage done. And there really isn't a better way to find the leak(s).

[leddzepp]

Bars leaks has stopped every leak I have ever had coming from a radiator.

[DipStick82]

Any one else used Bars Leaks? Sounds great if it works, which sounds like it does, but also seems like a "band0aid" ? Anyone know how it works?

Stepping out to watch the engine run and see if I can track down that leak!

[68panelman]

It is essentially a Band-Aid that sometimes can be permanent. I would just always know it's there holding and could potentially let loose when you least expect it.

[DipStick82]

anyone recommend a gasket sealer like loctite? this is for when i replace the thermostat.

[68panelman]

I use the permatex copper sealant. High temp and good for many gasket surfaces.

[DipStick82]

Do you guys use this in addition to a gasket like what NoNeck recommended above? NoNeck what about you?

Thanks everyone'n

[68panelman]

Depends on mating surface conditions, sometimes they'll have pitting/ uneven surface. I use with gasket, and a thin i MEAN THIN layer of sealant

[hamjet]

I like INDIAN HEAD shellack for the thermostat housing gaskets and inside the radiator hoses. used it since I was a youngster..

[swamp rat]

Cant help but notice the rust on the back side of the water port on that intake manifold, are you sure all the intake manafold bolts are tight? the installer used the proper sealant on the bolt threads going into the water jackets?? that area of the intake will leak around the threads if not sealed correctly, that will lead to the gasket deteriating around the water port of you used gaskets like Mr Gasket.

The red silicone on the build was probably not the best choice for the intake manafold or water pump.

[NoNeck]

Sorry, but I would not use Barrs Leak. Additives (bottled fixes) are a multibillion dollar business in the USA. Rarely does one actually work yet there are a lot of folks that swear by them.

The placebo effect is what is in most of these snake oils and a lot of them can do damage. Can't tell you how many engines I've seen with semi-clogged coolant passages and compromised water pump impellers from these products. There are few additives or fixes in a bottle that are nothing more than naptha, alcohol, and pale oil. If it says "petroleum distillates" on the bottle, now you know. A radiator fix in a bottle is going to plug a lot of things and depending on the engine can cut off vital coolant to areas. Once you put this stuff in, it's a pain to get out.

Same with these radiator additives that are suppose to cut surface tension and make coolant more effective. Once in the engine I can assure you that electrolysis will start and things will suddenly start to corrode. They fix- sell the vehicle because it ain't comin' out cause it's in the metal and you've screwed it up. Got a coolant leak - take it to a shop and have it fixed right.

As far as sealants, I would use black silicone for paper thermostat gaskets. Better quality gaskets like the FelPro I mentioned wouldn't need a sealant because it features a ring of sealant embedded in the gasket.

I have attached a photo to help you see what goes on under that thermostat housing. I hope this helps.

Good luck,

POP