My Z tends to heat up on the freeway going about 80mph, and going up mountainous freeways. I changed the thurmostat, it was old, and the fan clutch, it was spinning backwards way too easy. It's still running hot. This morning I turned the car on and opened the radiator cap. I looked inside and the coolent running inside wasn't moving. It was stagnant. When the thurmostat opened the water started to rise. So I turned off the car and put the cap on. I don't want to drive it until I fix it. I don't know the mechanical history of this Z but the water pump doesn't look too old. I'm thinking it's the radiator...but then again, it could be the water pump. Any suggestions.

 

Try flushing the radiator with a hose. Just put it through the top inlet and see if the water immediately begins to flow from the lower outlet. If it does than your radiator isn't blocked up. If it trickes out or takes a while to come out the bottom, then try flushing it with a flush you can buy at autoparts stores. If that doesn't help you'll need a new radiator.

If the radiator checks out, then it could be your waterpump. If the bearings start to go out, the impellor can start to rub on the front engine cover where the pump mounts and create a gap so the water doesn't get directed to the engine. Waterpumps dont usually just stop pumping water though. They'll leak, and bearing go bad, but the impeller would have to shear from it's axis or loose a fin to stop pumping water. You could also have blockage in the motor somewhere too, but that's unlikely if you keep antifreeze in the system and not just water. When you flush, it should clear up any corrosion in the engine itself.

 

Oh, one more thing, check the belt. If its slipping then the waterpump wont be able to pump the water at the rate necessary to keep up with the engine at high RPM's. If there's any doubt, replace it. Listen for any noise from the water pump too. That would indicate worn bearings. And check the weep holes to see if you have any signs of leakage which would mean the pump needs to be replaced. Change the thermostat too, if it's unable to stay open, it would inhibit cooling. And, something else about thermostats that get overlooked, is if it is staying wide open, the coolant can circulate faster than the radiator can cool it which would cause the engine to heat up on long drives, but usually won't cause it to heat up to the point of damage. Just a couple more things to look for.

 

With a car I'm gonna keep for a very long while should I just do both the radiator and the water pump.

 

Have you checked the timing? I have no experience of this on a Z, but I once had the same problem on a 1966 Datsun Bluebird. Ended up that the timing was way retarded, once I adjusted it the overheating was cured.

 

I did check the timing. Unplugged the vaccume advance and the distributor harnest as instructed by the FSM. I set it as 8+ or minus 2. Checked it again yesterday and that was fine. Although it was really retarded. What trubles me it that I don't see the coolent moving inside the radiator and I have always seen it move in all my cars or trucks

 

I meant to say it was retarded before I set it last week.

 

A new water pump is always good insurance against failure of an old one. Knowing your water pump is going out is going to require you to pay attention to it. It's not going to give you really obvious signs until it's probably too late. Plus you can get a rebuilt unit for less than $20. As for the radiator, a radiator in a properly maintained cooling system can last the life of the vehicle. So unless you come to the conclusion it's bad, I wouldn't replace it. If it's got a lot of heavy corrosion or it is infact blocked up, then I'd replace it. As far as seeing the coolant flow; not neccesarily. It doesn't appear to flow across the radiator in all cars, although some you can see it rushing by the filler. If it wasn't flowing at all though, the car would just keep heating up from the moment you start and just left it idleing. Not just on long drives and mountain climbs.

 

Oh, and how hot does it get? Are we talking 195degrees, in the red, or pegged? If its creeping over the midpoint by a few mm's, than it's probably just the little deficiencies of an aging cooling system, and not a major problem. For the sake of a restoration, you could replace any part of the cooling system that isn't in tip top shape if the car is going to be in your possesion for a really long time to come. If thats within your budget. It's up to you. If you want that showroom new restoration in your driveway, then by all means replace the water pump, and radiator, and the hoses(speaking of which, check their condition, if one is compressing shut after it heats up that would also cause a restriction of flow), you should replace the belt if you're not sure of it's age, thermostat, the works. Not everyone can afford to do all this. But atleast you'll know everything is brand new. Oh and a quick way to check if the coolant is flowing, wait til the therm. opens, the squeeze the top hose for a sec and release, there should be a surge of coolant. If not, then it's not flowing right.

 

I know the thermostat is opening because I repaced it and I guess the water pump is pumping because it went up therm and into the raidator, but just as the therm openend the coolant started to rise.

 

A lot of times brand new thermostats wont even work correctly. We had to replace a thermostat in a Jeep twice because the new one didnt open.

 

I was checking it out again last night and the therm is opening I could feel it flowing through the top hose...and I could see it flowing in the radiator. I guess I didn't wait for the them to open...I think the heating up going up mouintainous terrain will be taken care of by flushing the system. I don't know when was the last time that was done. I really don't like not knowing the mechanical history of my cars.

 

well since ive replaced both my radiator hoses pump and thrmostat .. i must say i dont even get to halfway when im driving.. a cooling system replacement is a great investment into these engines and if you just take care of them, theyll last a lifetime..

 

oh and btw.. the water pump belt also runs the alternator.. if it was loose, youd have electrical problems more than anything.. always make sure that belt is on there properly

 

You are absolutely right! I just don't have the time right now, but when I do...its water pump, radiator, new top and bottom hoses, and some gatorback belts. Hopefully all it needs it just a flush.

 

Don't overlook those hoses though. Like I said, if that lower hose is compressing itself under pressure and heat then it will restrict the flow of coolant. You might not be able to tell when the car is just sitting there though. Just give her a squeeze and see if it's firm or collapses easily. A good lower hose will have a coil running through it to prevent collapse even as the rubber degrades. But a flush is always a good idea. I replace as much as I can afford on an old car, because you just never know the history or how old each part is. I've got every receipt for every part I've ever bought for my Z. Even stupid little things. And Thermostats can definitely come defective, I've seen that happen several times and once to my own car (not on the Z though). Oh, and it's also important that you position the thermostat properly so that air can vent out of the system. Air trapped in your cooling system can cause hotspots.

 

Oh yeah one more thing that wasn't mentioned yet. The radiator cap. Have it pressure tested. If the cap isn't holding pressure then the system isn't going to work as effectively as it should. In most cases its not enough to cause your car to peg the red everytime you drive, but it will cause it run at a higher than normal temp, especially under heavy load.

 

Yes definately check the radiator cap, like fairlady said. I had it happen to my '81 before, and he was practically pegged all the way over! And I did anything else I could think of replacing that needed it. But never thought to check the cap, until somebody at an Auto Zone told me. And sure enough, it helped the car out. And it didn't get that hot after that.

 

I'm going to check that lower hose. So far I've changed the cap, fan clutch, and I got one of those new fangled thermustats. And I made sure that the air hose is on the drivers side... I check that out with the FSM. With my 16 hour days it's been a challenge to do the more involved stuff. I'm going to flush the system today and see what happens.

 

Well,

I'm running cool again...between 140 and 18O at the most. Even on a day that had record setting temps in the bay area. Up the mountain in scourching heat, not problem. I changed the water pump, clutch fan, radiator, thermostat, and both hoses.

Thank you all for you advice. And keep it running cool.

 

This works pretty good...

 

what kinda water pump is that?? looks pretty spiffy..

btw davidjoe... glad to hear all is running well.. a cooling system treatment is one of the best long term investments.. i never reach half...

 

[QUOTE=assimilated420]what kinda water pump is that?? looks pretty spiffy..

That is the electric one they sell at MSA..

 

Looks like a CSR. Where'd you get it? I hope you didn't buy it directly from MSA...?

$236 at SummitRacing.com

http://store.summitracing.com/defaul...=egnsearch.asp

 

Wow... how well does that work? I also changed the radiator cap. Funny to think of all the stuff that gets changed with a job like that. But I am really happy with the results.