Baker

1997 F150 4x4 4.6L. Pushing 85,000 miles ( yes that's correct ). Heater core replaced Jan 2009 by independent at 54,000 miles. Replaced again at 68,000 on Dec 2010 by Ford dealer. This morning the heater was weak on output. I have seen several suggestions online from changing thermostat to 195, flush system, burp cooling system, check blend door, etc. Anything else? Can I even see the blend door open/close under the dash? Thank you...

digitaltrucker

cant a defective fan clutch impact heat?

jstockert

Yes you can check blend door. There are you tube videos that show you where to cut the plenum box behind glove box and use foil ac tape to repair. I did and have no problems with air escaping from cut.

Baker

Several things have happened since the original post about the weak heater output. Cooling system down about 1.5 gallons. I don't look under the hood much because I don't drive much. It has taken me since Feb 2014 to almost drive 5k for my next oil change. I refilled the system with Prestone and distilled water around 50/50. Heater works great but now I have a puddle of coolant under the truck. Took it to the dealer for a pressure test and now there is a pinhole in the cylinder head on the drivers side 3-4 inches below the thermostat. He showed it to me spurting out. Dealer wants $3900 to replace the one head, I said NO! An independent shop owner said he has dealt with this before on this model engine. Before I told him the location of the leak he said front of head by the thermostat housing. He repaired his engine with JB Weld. He took out the thermostat and cleaned real good on both sides of the head. He said the weld held for 2 years and then another pinhole popped up somewhere else. He said it was a bad casting to begin with. Anybody else with cylinder head pinhole problems on their 4.6L engines? I keep getting asked the VIN # for this engine. What is it or where can I find it? Thanks.....

jstockert

The vin number is located on the driver side of truck. Look thur the lower corner of windshield and you will vin. It is also on your insurance card. That is if you have insurance.
On the other hand trying the jb weld is worth a shot.

BossRacing71

One possibility you might wanna check out is that your heater core could be getting clogged up with sediment. Pull your heater hoses, and then blast some water or air through one, then the other. You might have to do this a few times to make sure it's cleared out. Just did this on my 97, and all kinds of neat stuff came out. Although getting to the hose connections on the firewall is a bit time consuming, it's way better than having to tear into your dash for a heater core, IF you don't need one.

Just my .02

TRD-Toy

Had this same thing happen on a V10. Ate the thermostat housing and the intake manifold too. Was leaking externally below the housing in the head. Was caused by excessive electrolisis. Might want to check voltage on your cooling system. With an ohm meter check voltage in the coolant reservoir. This truck showed 2.3 volts. I'd check the thermostat housing and intake for scoring or the metal. Also check the water pump. Might be causing cavitation which also can lead to pitting and scoring of metals.

jkenprice1

Kind of a tough call on the repair. Since you don't drive the truck a lot, the JBWeld might last quite while. Another thing you can do is add antifreeze conditioner. It helps reduce electrolisis.

Brianmcg321

WateR pump.

Baker

Removing the air cleaner and stuff to get a good look at where the leak is. Below the thermostat housing it appears there is another gasket that might be part of the manifold. The coolant is squirting out from that gasket/seam area. What is in that area that requires a gasket for coolant or am I just seeing a casting seam? Thanks....

This gasket/seam where the leak appears is about 2" below the thermostat gasket.