Cooling system casuality on my MK IV build

[JayMagness46]

After 24 months I just completed most of the mechanical phase of my MK IV build, placed the body on the car and had Reliable Carriers transport it to my second home in Western NC. The drive train is a Blue Print 347 w/Holly Sniper and a Tremac TKO 600 transmission. It is my intent to finish some minimal remaining mechanical work and then get to work on the body. I have a very good body shop with a painter I have known for over 40 years. HOWEVER, before I can get to that I have a problem.

For the first several starts of the engine it ran perfectly. The engine turned over twice and fired on the first start. Once I mapped the EFI with the Sniper hand-held, the engine has been flawless. On previous starts the engine gets up to temperature (about 90 deg C), the electric fan cuts in and the temperature cycles from about 85 deg C to 90 deg C. Up to this point everything is fine. I haven’t had a single leak of any fluid: fuel, brake or coolant. Last week the problem began. As soon as the engine gets to 90 deg C and the electric fan cuts on the upper radiator hose on the engine side at the thermostat housing blows off and throws coolant everywhere! I tried replacing and doubling the hose clamps, and still it happens.

Does anyone have any experience with this? In advance, thanks for the sage advice I know I am going to get.

Jay

[NAZ]

First, ensure that the hose is the correct I.D. for the fitting. Then ensure the mating surfaces are clean and free of anything that would act as a lubricant (coolant, grease, oil, etc.). Then if you need more clamping force use aerospace style t-bolt clamps and double them up for really difficult to seal joints. https://www.summitracing.com/parts/vpe-2789 Remember, these clamps are sized for the O.D. of the hose not the hose size (hose and pipe are measured by nominal I.D., tubing is measured by O.D. -- this can be confusing for many).

Good luck.

[ydousurf]

Jay, I agree with what NAZ advised. However, you may also have a bad or broken thermostat and/or possibly it was installed backwards? I'm thinking the heat (pressure) building up scenario. Just some thoughts...

Dj

[Norm B]

In addition to the recommendations above, check that your rad cap and overflow system is working properly. Is it possible the system has drawn in some air while cooling between starts? Air pockets in the heads will create hot spots that cause an immediate boil over as soon as the coolant starts flowing. Do you have the bypass hose installed between the water neck and the water pump?
If you could post a picture of the water neck area maybe one of us can see something amiss.

HTH

Norm

[BadAsp427]

This is a very common issue. The problem is that the lip on the chrome T-stat housing that BluePrint puts on the engine is all but nonexistent. Thus the hose / clamp have nothing to hold it on and it can just slide off. A simple fix is to put 2 or 3 self taping button head screws in the housing and then put the hose back on. Then the clamp has something to hold it on with. Now, you also need to check ALL of your hose clamps after every full temp run of your engine for the first 3 - 5 times. You will find they will all need some tightening after each run. Ask me how I know. And for what it's worth, if you do a search for this problem, you will find it in many different posts.

[JayMagness46]

Thanks for the assistance. Just what I was looking for. I will post some pictures tomorrow.

Also, comparing the overflow tank that came with my FFR parts, it does not match the one that is shown in the build manual. The build manual item has two tubes that exit the bottom of the tank: one to receive coolant from the fixture attached to the radiator cap and one to vent & discharge overflow. I am wondering if there might be some unusual pressure building is the expanding coolant has nowhere to go and can’t enter the overflow tank. Just thinking.

Jay

[Fman]

If you end up replacing the water neck this will be your friend. I had a china wuhan special water neck initially on my 427 and it was POS and nothing but headaches. The Ford water neck is 100% worth every penny.

https://www.cjponyparts.com/ford-racing-thermostat-housing-90-degree-302-351w-1979-1995/p/M8592M90/?utm_source=Pony&utm_medium=Email&utm_campaign=OrderConfirmation&lac_guid=f155fb95-9b1f-eb11-834d-0050568938fc

I also ended up using Vibrant T-bolt clamps on my engine.

You need the 2789 clamps for the water neck and all other clamping junctions with exception of one 2790 for lower water pump which is slightly larger in diameter.

https://www.summitracing.com/parts/vpe-2789
https://www.summitracing.com/parts/vpe-2790

[NAZ]

[QUOTE=JayMagness46;439743]Thanks for the assistance. Just what I was looking for. I will post some pictures tomorrow.

Also, comparing the overflow tank that came with my FFR parts, it does not match the one that is shown in the build manual. The build manual item has two tubes that exit the bottom of the tank: one to receive coolant from the fixture attached to the radiator cap and one to vent & discharge overflow. I am wondering if there might be some unusual pressure building is the expanding coolant has nowhere to go and can’t enter the overflow tank. Just thinking.

If that recovery tank does not have a vent to atmosphere that WILL not allow excess pressure to bleed off and could very well cause a hose to blow (or other worse things to happen). A recovery tank needs to have a vent (usually the overflow -- sometime both overflow and air vent).

[D Stand]

Have you tested your radiator cap? The cap is what will open up from the filler neck to the tank. You should be able to rent, from your local auto parts store, a coolant system tester. You can test the cap to make sure it is opening at the right pressure as well as pressurize the system to that pressure or more to help troubleshoot.

[Boydster]

Is it possible that the first pop-off was due to a clamp loosening up (ALL of mine were loose after a few heat cycles and had to be tightened... every. single. one.) and when you put it back on, there remained some of the greasiness of the coolant so then it proceeded to pop-off again and again? Maybe sandpaper on the water neck, then cleaning very well... anyways, maybe.

[BEAR-AvHistory]

The chrome thermostat housings have been crap since I started with cars in the 1950's. If they did not drop the hose they leaked at the gasket. Plain old stock part is a good plan.

[MSumners]

I can’t tell from the images on the site, does the stock Ford water neck Fman referenced above have an NPT fitting threaded in addition to the outlet?

[Fman]

I can’t tell from the images on the site, does the stock Ford water neck Fman referenced above have an NPT fitting threaded in addition to the outlet?

It has a plug port but it is not threaded. You would need to drill and tap it.