I was driving my truck yesterday and the temp was running about 1/3 the way up (was only 3 miles from the house) and started up a hill and all of a sudden the temp gauge just shot right up to hot (no climbing went from normal to pegged).Stopped overflow was boiling over.turn cap slowly and let air out.Got back in started truck up temp was back to normal. Turned around and took it home.So today added some anti freeze and let truck run in driveway for a hour and temp gauge only went to 1/3 of the way up drove it around a few miles and seemed fine.Well about a hour later left the house and started up a hill only 2 miles from house and the temp went from 1/3 to pegged.Pulled over over flow was boiling again relieved pressure turned around and parked it.I changed the anti-freeze amd t stat about 2 month ago.The anti-freezr is rust color still.When I changed it I even took a hose and put it on the t sat hole, and water just kept coming out rust color.Do you think I should flush the radiator or do you think I have a head gasket problem? Seems the heat is hotter when driving it then when I am parked.

 

Well I just had almost the same symptoms and mine was a head gasket. I finally went and had a Hydrocarbon test performed on the coolant and it showed hydrocarbons in the coolant from a blown head gasket. I'm not saying thats your problem but a hydrocarbon test will show one way or another. Good luck.

 

SO have you changed the head gasket yet?I am pretty could at doing this kind of work, just not sure if I want to tackle that big of a job.Where did you get hydrocarbon test kit?

 

The only place around me that had a kit was NAPA $43.00. I just took my truck into a shop that performed the test and a coolant system pressure test for $75.00. Yes I just finished today changing both heads, gaskets, and intake manifold to PI on my 97 4.6. Around 18 hours doing it by myself. Two guys would make a big difference.

 

Did you have the heads machined?and did you use the head bolts or buy new?I know the gasket kits runs $200 what else did you need to get.Did you run into any major problems? Called Autozone, they rent the Block Test Kit out, so I am going to go grab that tonight.

 

I had a set of PI heads and intake that had very low mileage on them. I also used new head bolts that I already had for a while. You can reuse the head bolts however.I know some will say no but having worked with the bolt supplier we were told by them that they are reusable. Your call on that. I also installed new exhaust manifolds while I was at it. If you remove the two nuts that hold the exhaust crossover to the frame you can move the entire exhaust back about 2 inches. This will give you enough room to pull the heads with exhaust manifolds intact. Also reinstall the new heads with exhaust manifolds installed. Beats trying to install them after the heads are on the block, big time saver. I used Felpro head gaskets and get the gaskets that are listed for the truck year not for the new heads if you are going power improved. Also put the gaskets in place on the block and double check that all oil passages and coolant passages line up with the gasket holes. Then do the same thing with the heads.

 

OK, did the block test kit twice after truck was running for 20-25 minutes and fluid stayed blue.When I had it running I had the cab off and then I seen anti-freeze dripping, but not out the top, unless it was a huge ait bubble.Also when I did the test I noticed the upper radiator hose was collasping when I was using the block test kit.Upper hose was not hot.So I waited alittle while and pulled t-stat. Well the anti freeze in the housing was hot, and the anti-freese in the rad end hose was stone cold.So I either have a bad t-stat or a circulation problem.Need to figure out which one.I also noticed that little air hole is t stat with had crap on it.I am thinking about doing a good cooling system flush and then work from there.

 

If it's that crapped up, I'd get a professional flush job.

 

Check the water pump while things are apart. The impeller vanes could be the problem if they are rusting. Not enough coolant flow when you work the engine hard like climbing a hill.

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OK, flushed out the cooling system with water and some cleaner.Put a new t-stat in, has not over heated since I done this, but I noticed a new problem.I do not get unless I drive down the road, the I gets nice and hot, then when I slow down in traffic the air cools down, as soon as I gte some rpms the air gets hotter.So I am thinking it is either a water pump flow problem, or maybe a blocked heater core.I did read somewheres on this site about a brass reducer in a heater core line that gets plugged.How do I remove the heater core hoses to flush the heater core with some compressed air? I would just un hook the hoses, but the one that goes to the back of the motor has the original clamp on in and it is against the fire wall so I can get anything on it to compress it to remove it.

 

I use long nose vice grips.



Regards

Jean Marc Chartier

 

JMC, do you think the fins being warn down would cause the low heat at idle speeds and the pump circulate when rpms increase or do you thing heater core may have a blockage?

 

Try burping all of the air out of the system first. Cold engine remove the degass bottle cap. Start engine and let it idle till the gage reaches normal temperature reading. Turn HVAC to vent and full hot with the blower on full.let it idle for a few minutes. If any air is trapped in the system this should get it all out.

Regards

Jean Marc Chartier

 

Well did that and the heat still does the same thing.Ok, I noticed that once I get up to 2000 RPM'S the heat rolls out veyr nice, under the 2000 rpms the heat cools down.I am thinking about what you said the fins on the water pump could be worn down, and when I get higher rpms the water pumps spins faster so is pushes the collant around faster.