Coolant Woes

[Mike_Windsor]

Hi everyone, I have a problem.

Wait, come back.

Okay, so, I've noticed that when starting my car up it takes about 5 minutes for the water gauge to come to life, and it generally springs from resting to about 160F, then it'll rise up to about 210-220, then jump down to 180F, and so on until it normalizes between 205 and 215.

I was told this might be a malfunctioning thermostat, and possibly a failing heater core.

Today I looked under the hood and saw a small puddle of coolant sitting on top of the intake manifold.


Could it be blown head gaskets?

I went ahead and bought a new thermostat and gasket for it, should I replace the housing too?

What are your thoughts?

It's a 351W 5.8L.

[johnunit]

Where on top of the intake?

I doubt it's a head gasket, those almost never fail on our cars.

[Mike_Windsor]

Near the thermostat housing I think.

[johnunit]

The housing itself is a common leak point. Mine is corroded on the sealing surface and has now leaked twice. Simple fix, 2 bolts and the hoses.

[Mike_Windsor]

Thanks.

What about the surging/lagging temperature? Bad thermostat?

[johnunit]

Could be, but if you're loosing coolant, that'll throw off the temp reading. The temperature sender is pretty high up in the cooling system, and if it isn't fully immersed in coolant the reading will be off. Either way, typically people replace the thermostat every time they take the t-stat housing off.

If it's the t-stat housing, you'll likely see it collecting right below the housing, behind the water pump. You'll also get some slime or staining near the gasket.

[Mike_Windsor]

I'm just gonna replace the housing along with the thermostat and gasket.

Hopefully that's all it is.

[johnunit]

That's where I'd start.

Don't use the paper gaskets. Either get something made of rubber or use a gasket maker liquid specifically designed for coolant applications. I think Canadian Tire actually stocks one listed as for thermostats and water pumps. Failing that, black RTV is a good alternative.

While you have the housing off, check for pitting. There should be a raised ring on the sealing surface of the housing and that raised area should be unbroken.

[Mike_Windsor]

The gasket I got is blue looking, feels like it might not be rubber.

I got it at Canadian Tire, even.

[gadget73]

I've had fair luck with the heavy paper self-stick gaskets. Tip to make this easier, loop a piece of string through the thermostat and use that to hold it in position. The thermostat has to sit in the little groove in the housing, and it doesn't like to stay there. If its out of position, it will piss coolant like mad. The self-stick gasket helps with this. You can assemble it all, stick the gasket on there, and it helps hold it all where it goes. You will need to make sure the housing and the surface it seals to are clean of any old gasket material though, or it has no hope. If its got dings and dents, see if it will file flat. If its got low spots, you may need some sealer to make up for the damage.

[Mike_Windsor]

What kind of file should I use for this?

[Mike_Windsor]

Well the new housing keeps leaking when I put it back together. Seems the thermostat keeps shifting as I tighten the bolts.

[gadget73]

a flat mill file, at least a 6" but a longer one might be better. The goal is to knock down any high spots, not grind away at it. Careful, light strokes are what you want. If you don't have a file, 220 or finer sandpaper on a wood block will do the job as well. It just has to be flat and free of any gasket material or burrs in the metal that interfere with sealing.

try a self-stick gasket if you didn't already. It makes this a lot less annoying.

[Mike_Windsor]

Finally got it!

I have heat once again and my car runs at a cool 195 degrees F.


Well, that was easy.

[kishy]

Out of curiosity, does the 351 have the same failure of a design where one of the thermostat housing bolts is nearly inaccessible due to the water pump?

As for the paper gaskets, at least for 302 applications both older and newer, there is only a paper one (and the Fel-Pro one happens to be blue), but one could certainly buy a sheet and cut it out...I found the paper one leaks if it's installed dry, it leaks with RTV, but it seems not to leak if you use the spray gasket adhesive (Permatex Ultra Copper in my case). The problem is that it may be a much bigger pain to remove later using that stuff.