w3lfd

1982 4.5 US

Well, the car I purchased in non-running condition is finally running, but now that it runs, it overheats. I flow checked the radiator and it is letting hose water through without any problems. I replaced the thermostat, though I suspect the old one was working fine. Replaced the cap on the radiatior tank. Here are my symptoms as it stands :

Filled the system, worked on burping the air out by manipulating the radiator hoses. Ran it a little (about a min) with the cap off, burped some more.

Now, I can let the motor run till the temp climbs clear past the last white line, and I get no heat out of the heater, and the lower rad hose remains cold, but highly pressurized. Top hose is super-hot.

Any suggestions of what this could be besides the water pump? I'd like to exhaust everything else before I dig into that project.

the flyin' scotsman

Is the thermostat the right way around?

w3lfd

yup, it is. Per the shop manuals (and common sense )

marton

replace the little heater hose between the back of the block and the heater valve with a longer transparent hose; you will quickly see if the pump works. Of course you need the heater switched full on and to check the heater valve opened OK.

Marton

FlyingDog

Take the belt off the WP and see how it spins. Also a good time to look for burn marks or belt shavings to indicate a seized or damaged pump.

SteveG

Did it sit w/o water in it for a long period of time? It could be stuck, happened to me. Actually doesn't matter, I would take it out, put it in boiling water (bring it up slowly and watch it open, if you have thermometer you will know the temp) and see if it opens or just replace.

w3lfd

Clear hose is a good idea, I have my doubts as to whether the valve is actually working.

After that I guess I will start pulling stuff off to check out the pump. Once I try your suggestions, if it is the pump, I guess I may as well do the TB at the same time.

The thermostat is new, SteveG (if that's what you were referring to)

Thanks all, I will keep you updated.

SharkSkin

Pull the hoses off the radiator and see if water comes out the lower fitting when you stick a garden hose in the upper fitting. The rad could be clogged, and it's a lot easier to check this than the pump.

mark kibort

you have to force the thermostat open, (ask me how) then, you remove the hose connecting to the thermostat housing, and vent it to the side of the car. take a spare hose and use it to pour water into the thermostat housing. this way, you kill two birds with one stone. you see if the radiator is clogged and if it is, you then by pass it and connect the upper radiator hose to the thermostat housing inlet with a clear hose to see if the pump is working.

you have to isolate the problem.

mk

w3lfd

Already flow checked the radiator in that exact fashion.


Also, I had already pegged open the thermostat to run it to check before I got the new thermostat. Problem is, I am not going to be able to source a clear hose big enough to fit up front to test the flow there. I live in a rinky dink town.

maybe an autozone or somewhere like that might have one. I think that would also help me to be able to tell if there is still air hanging out in the system.

SharkSkin

The thermostat must be closed for proper flow through the radiator. If it's pegged open the car will overheat. I know that sounds crazy, but that's the way they designed it.

Big AL in VA

Same exact sympton as my old overheating issue. You probably have a bad water pump. Impeller is spinning on the shaft. The danger here is possible cutting into the block (metal impeller). If you have access to a machnists stethoscope, (spelling?) you may here this problem. Mine was intermittently catching the shaft.
Good luck.

Big AL from VA
84 EURO 928 S2 twin distributor monster

dr bob

I had the same symptoms after the last coolant change. I''d blown the top hose off the radiator and spewed all the coolant out, so it was time for new anyway. Back to the problem-- Rev the engine to get enough flow to move the air out of the water bridge. Thermostat will stay in bypass position until it gets hot, and it won't get hot if there's an air bubble in the bridge. Looking back, I could have pulled one of the temp senders off during refill to purge the bubble. Reving the engine during warm-up did the trick for me finally. The little bypass vent to the reservoir didn't seem to help much, for some reason-- might be because it's below the top of the bridge.

mark kibort

Terminology. when i say pegged open, i mean thermostat needs to be pegged open, sealing the short circuit return where the radiator is ignored. also ignored if the thermostat is stuck closed. closed meaning, you cant see through it. if pegged open, the back of the t-stat seals the top of the block and alows the water pump to flow water to the radiator.

how you peg the thermostat open, is to open it up against the spring and put a little electric motor spur gear (like used on model electric gear motors) on the top of the thermostat shaft. this pegs the themostat open. (you can see through it) this simulates the car when hot.

Mk

mark kibort

not a good test. scots felt just fine, and the impeller had backed out off the shaft, not even slipping on the shaft, but far enough off the shaft to make an air pocket so the pump impeller couldnt grab any water for high output flow due to a large gap between housing and impeller. however, we found the issue due to the pump leaking. so, there is another variable for you . by the way, the impeller gouged the block pretty bad, but fine for high rpm race conditions. If it hadnt been leaking, we would have replaced radiator, and other things

mk