Im back still overheating just a quick question probably a stupid one but on the 86 is the water pump suppose to draw from the top or the bottom of the radiator? the first water pump I put on drew from the top and was sucking the top hose shut and over heated quickly so I thought I had the wrong pump in it ( it was a corvette water pump) so I put a regular 350 water pump in it now it draws from the bottom and I can get by so long as I dont sit in traffic too long or go to fast for too long, either way then it will get hot. I just got to thinking maybe I had the right pump in it at the beginning but had too much air in the system? so can anyone tell me if the 1986 water pump is suppose to draw from the top of the radiator? doesnt sound right to me but I am completely out of thing to try and new parts to buy!

thanks

 

It drawscoolant from the bottom of the radiator, through the block, up through the heads, into the intake, and back to the radiator through the tophose. As far as over heating, is the cooling fan coming on? What temp do you consider to be overheating? It'snormal for one to run around 220 or so, especially in stop & go city traffic.

 

rshiver,
Since you mentioned that 220 degrees is normal, and in a previous thread mech259, I think, said that the cooling fan does not come on until the temp reaches 230, it got me to thinking.......oh oh. I guess I am kinda old school, but isn't this a bit high. I remember changing my thermostat on my 396 Chevelle from a 185 to a 165 to try to get it to run cooler. Is this high temp some sort of emissions thing? Does anybody know how to get the fan to come on sooner, other than hard wiring it to be on all the time? Would it be bad to have it come on sooner? Any thoughts on this?

 

well since I dont drive it very far at a time it doesnt technically overheat, but if I were to just let it sit and idle it will keep heating up till it fries the engine I havent let it get that hot but at 250 it starts boiling over and the fans are working I am running a 160 degree thermostat in it at the moment just because it takes alot longer to climb in temperature once the thermostat opens

 

Hi Goat & BigJon, the cooling fan on my 85 comes on at 224 degrees, and runs around 180 - 184 on the open road. They do make a fan switch that will make the cooling fan come on sooner, Ecklers has them http://www.ecklers.com/search.asp?action=freeSearch&free_text=fan%20s witch&yearConstraint=1986&searchHistory=

My opinion on the 165 degree thermostat verses the 185 is this.Running a 165 thermostat in an engine that naturally runs at a higher operating temp of 180 degreesor more is useless in my opinion, especially if you live in a warmer climate.Once the coolant temp gets above 165 degrees, you may as well not even have a thermostat becausethe thermostatwill stay open all the time, not allowing the waterto stay inthe radiatorlong enough tocool off before returning to the engine.

BigJon, 250 degrees is too hot if you ask me, it shouldn't be getting that hot. Have you checked to make sure the air flow through the radiator is not restricted? Has the radiator ever been "rodded" (taken to a radiator shop and have the inside water passages cleaned)?Other things that can cause chronic overheating is stopped up or restricted water passages inside the engine. I have seen water passages stopped completely up from using "radiator stop leak products", not onlywill the stuff stopa leak in the radiator, it will also clog upthe water passage between theengine block and the cylinder heads too. Are you losing any coolant? Other serious causes could include a cracked head or blown head gasket, allowing combustion gasses to enter the cooling system. Make sure the radiator cap is in good working order, it should maintain around 15 psi of pressure in the radiator.

 

I apologize its been forever since my first post with this issue but those who have been around know what I have been through with this car the engine is completely new including hot tank and built from bottom up, the radiator was rodded then replaced thinking maybe the pinched off some vanes the condensor was also replaced so there is absolutely no jam in the radiator/condensor area second new water pump and I have great flow through the radiator and have had everything from 200 degree to 160 degree and everything in between as far as thermostats go as far as the hotter thermostats are concerned it just gets hotter faster to the thermostat temperature, and then just has alot less range to go before boiling over I can drive the car to work and back even in the summer here in arizona with the 160 thermostat so long as I can keep moving it still gets to about 205 to 210 when I get home but with the hotter thermostats I cant even drive the car in the summer here. just alittle history and by no means do I think I know it all or I wouldnt be here but I have been working on everything from cars to heavy equipment for a a hobby and then a living for over 25 years, and eventually have figured out even what the dealers and so called professionals couldnt but this one has got me stumped. I bought the car in the winter months so I didnt think much of it till its first summer 5 years ago and it overheated then, the car is basically brand new at this point except for the rear differential and still the overheating problem I gave up posting about a year ago when I was here alot trying to look for anything I may have missed but so far no luck. it is such a basic simple system and everything seems to be working as it should but still the overheating. not a simple fix here I am afraid. it is still the same block hot tanked and freshly rebuilt and as I said great flow through the radiator, but I am almost to the point of buying a crate motor to drop in but afraid I will only be throwing more money into the car to no avail. Thanks for listening

 

Wow!! The only other thing I can think of at the moment to check, and you've probably already thought of it, is the "air dam" under the nose of the car that helps direct air up and through the radiator. If I think of anything else I will definitely post it.

 

Bottom radiator hoses can collapse,there's usually a wire coil inside the hoseto help prevent it. Just a thought

 

Air dam brand new, I too have thought of the bottom hose colapsing as thats what the top hose was doing when I had the wrong water pump in there, believe it or not though I havent changed out the bottom hose yet! LOL just thought maybe it was too far fetched also it will overheat at an idle when the hose isnt colapsing but I havent been able to look at it when driving at speed, I do know it doesnt have the spring in there now I guess with all the money I have spent it wouldnt hurt to throw a hose on there but let me ask you can I get just the inner spring somewhere because whereever I call they tell me my bottom hose doesnt have the spring in it ( another reason I havent changed it) I appreciate all the help though sooner or later someone is going to say something totally unrelated and the answer is just going to hit me like a ton of bricks!

 

I don't think anything would be too far fetched at this point. Is it possible that the ac condenser coils could be restricting air flow in any way? BTW, mine will heat up to 224 degrees if I just let it sit and idle, but cools down as soon as the fan kicks on. With everything that you have done, and being that you have good water circulation, I can't help but think that the problem has something to do with air flowthrough the radiator.

Edited to add, if you can't find the wire coil, you might be able to get a bottom hose that's corrugated. Just it being a new hose, it would probably stouter than the old one. At the very least, replacing the hose would rule that out as the problem.