I am still chasing my no heat problem. Changed out the water pump this morning. Old one looks like new. Installed a new one anyway. With the motor running, temp gauge at midpoint, water moving across the top of the radiator at 160 degrees, I can pull off either and both heat hoses at the firewall and there is no water. If I lay the hose down toward the ground, it will gravity drain the block and radiator, but no circulating hot water. No circulating hot water equals no heat in the cabin. Where do I look next?

Leonard

Edited December 19, 200915 yr by IdahoKidd

Leonard the only thing I can think of that can lead to your specific problem would be a clog somewhere. I can't see anything else causing the water not to flow towards the heater core. That is about all I can think of.

If my memory serves me right you own a 280z. If so try taking off the piping where the lower radiator hose connects to the block.(lower water neck I guess would be the name?) Take a look at all the lines and see if they are nice and open. Is you heater core clogged maybe?

Jan

The heater core is not clogged, and in fact, completely unhooked. The two hoses that go to it are unhooked with no stoppers. There is no water movement there. I have longer hoses attached so I can deal with them easier. If I raise the end of the hose up to level with the top of the hood, no water ever comes out. If I lay them on the floor, it will drain the block and the radiator. However, even the water in the block never gets very warm and I am fully convinced it heats the entire radiator to operating temperature before the thermostat opens, and I can't figure out how that could possibly be happening unless the pump is pushing backwards. You can't imagine the headache I have from trying to figure this out. And yes, it is a 77 280Z, bone stock except for the poor radio and the sunroof. I have ruled out, at least for now, these two as possible trouble spots:disappoin

Update: With a pressure washer, I was able to force water through the back of the head. I did get a small amount of rust colored water to come out but nothing I would consider significant. However, I do now have some water flow to the heater core, enough to actually defrost the windows and heat the cabin. The other issue remains, regardless of thermostat, the water temperature remains that of the entire radiator, about 160 degrees. At least I can drive it again.

Leonard from what you found it sounds to me like your block has a clog in it. To me if you had no flow prior to the flush and some flow afterwords the flush had something to do with the "fix". That being said, are you the original owner of the car? Have you (or the P.O) ever used any of that stop leak stuff?

Jan

I am not the original owner, I know the engine in the car came from a bone yard and know that it sat in the car, in a barn for at least 5 years before I got it. I agree there is or was a clog in a water jacket. What I can't figure out is why it has to heat the entire radiator to get any kind of engine temp. It literally takes 20-40 minutes to get a modest engine temp and that is with the rad 100% blocked. I have another completely rebuilt motor, nearly 5 grand worth, setting on an engine stand for a different project, but this motor runs so well....... I can't figure out why it doesn't overheat. I guess for now I keep driving it. Drove it all summer without issues other than it never got warm.

Your fan clutch might be stuck which leads to a slower warming up temp. If there's a clog in the water route there's a good chance that the clutch might also be clogged, since the car sat in the barn for 5 years.

Not the fan clutch either. Took it and the fan off. No difference. I'm telling you, I have a bloody forehead from beating it on the wall. Even the local shops just grin and tell me it isn't possible, even though they can see it with their own eyes. Removing the fan belt does bring the engine heat up so it really does make heat, it just looses it really fast.

Leonard one more idea I have. First off go around the engine with a temp sensor (laser type) and see if the engine is all at the same temperature. What I mean is make sure the front and rear of the engine are all at the same temp. It is possible that you still have a clog or something in the water jacket that restricts the flow.

I can't see any other reason why you engine should run so cold. Maybe a faulty temperature sensor is causing the engine to lean out the mixture prematurely.. This in theory would cause the engine to run cooler but again...just an idea.

Hope that helps

Jan

I was thinking along the same lines as Jan. It's possible that the flow reduction is not allowing enough of the heated water to the temp sensor or into the radiator. In other words, you're only getting enough heated water to the rad to semi-heat the water that's already in there. The infrared temp sensor on the block is a good idea to make sure you're not getting areas of extreme heat in isolated areas which could lead to a cracked block, warped head and other nasties. I recommend a reverse flush using some kind of cleaning or loosening agent to break free any built up corrosion in the internal passages. Something like this must exist but I normally just reverse flush with plain water from a hose. The reverse flow will help break free any debris that has been wedged in.

Edited December 21, 200915 yr by =Enigma=

just a shot and i could be full of **** but......

do you have any idea if this engine was ever rebuilt (diff head bolts or something out of stock like gasket color, etc)??

possibly the wrong head gasket was installed and is blocking some of the internal ports???

just came back in from the shop. Using a laser digital thermometer, temp readings are:

Thermostat housing 132

top of radiator 120

Midpoint of radiator through fan 96

Head temp above/at sparkplugs 162

Head temp at back of block 162

Upper heater hose at fire wall 91

Lower heater hose at fire wall 91

Temp at water temp sensor at block 132

Exhaust temp at collector 475

Temp at Y at water pump inlet 92

Temp gauge shows about 160. Has known good 190 thermostat.

These were taken a couple of days ago. I did a back flush and got just a hint of rust out, nothing substantial. It has prestone flush chemical in it now and supposed to run for 6 hours. Took it to a semi retired datsun tech who hasn't work on Z's since the 70's and we couldn't come up with much. Thinking that perhaps there is a crack or a break in the water jacket behind the water pump that is allowing the water to move back and forth without going to the thermostat. Gonna put on a coat and run it till it breaks. I've already driven it about 4000 miles in the past year and it hasn't broke. It makes no sense at all.....