Overheating issues in an 85... comments?

[flaboy]

I havent had my GN a week yet, and its allready giving me issues, but hey, i knew this was likely going into it So far my car has overheated on me twice... I ont have a temp guage in it as of yet (will in a week when the paycheck comes through) so I dont know any specifics as far as temps go. The first time was literally when I was driving it home after buying it. I was on the interstate doing about 70-75 for about 15 minutes or so when the light came on , and upon pulling over there was water puking out of the overflow tank. After letting it set and cool down, and topping off the coolant, I drove it around for 3 days with no problems, no light, didnt seem to be losing any more coolant. In those three days there were times where i drove it for mucyh longer time-wise then when it overheated, and wher ei had it idling for long periods with no issues, but it was also all at lower speeds (mostly city streets). Then today on the way to work it overheated again, same situation as before, I was runing at a high speed for a sustained period. So to drive back home from work i kept it under 60 the whole way home, and even stopped by two auto-parts stores to get some stuff, and when i aprked it in front of my house, it was fine, it hadnt lost any more coolant or anything, and the light never came on. So it seems to me the only times it is overheating is when I'm at a (relatively) high rate of speed, at which point it overheats relatively quickly, whereas if i keep it at lower speeds, i can drive or a good long while with no issues. I have a few ideas I wanna bounce around, and please feel free to tell me what you think. First off, it has a brand new water pump and thermostat installed, so im rpetty sure those arent the culprits (althoguh i guess its possible they could be defective units). I bought a new rad cap and a flush kit, and some Zerex Super Radiator Cleaner, the stuff you put in and let run through your system for 3-6 hours worth of normal driving then flush out, to clean out corrosion and scaling etc. I figure, if it solves my problem for 15 bucks, then great. If it doesnt, then hey, i only wasted 15 bucks, and its probably not a bad idea to clean out the radiator and put ona a new cap anyways. If it does not in fact solve my issues, my next thought would be possibly a collapsing radiator hose?? since at lower speeds the coolant wouldnt be circulating as fast, it would work fine, but only at the higher engine (and therefore water-pump) speeds, the pump is working hard enough to collapse one of the hoses? I ahd this happen on my old buick (67 GS). If anyone has any ideas or comments or anything, I would appreciate the help. And I know it would be best to get a new aluminum radiator and electric fans and all that jazz, but money is a little tight, so the solution im interested in right now is the cehapest one that effectively solves the problem. I'll spend what I need to to keep my car healthy, but Ic ant afford to spend any more than that at the moment, ya know? Thanks for the help, and my apologies for the long-azz post

[Grumpy]

dirt on the outside of the rad .. I flush mine out every now an then

[MaxVO2]

My thoughts if the above doesn't solve your problem:

Make sure your lower radiator hose has a spring inside of it to keep from collapsing at high flow rate. You can feel for it from the outside of the hose. Sometimes, people replace this hose with some generic part that could probably be used for the upper hose in other applications, so no spring is in it, or it has been removed.

Also, since the water pump is new, was it just a generic rebuilt pump? or new unit? Since the water pump on our cars is a two piece system with the front of the timing chain cover acting as the back of the pump, the clearance between these two surfaces is critical. If it is too great, this dramatically reduces pumping capacity, especially at higher speeds. The pump just cavitates. See if the water pump pulley lines up well with the other pulleys with this new pump. The pulley can be shimmed if needed. Too thick a gasket can cause problems, as can a pump whose mating surface has been milled down too much at the factory by accident. It's rare, but happens.

If the easier stuff like thermostat, air in system, radiator hose collapse checks, blown head gasket, etc.. doesn't pan out, and the radiator seems clean, and not needing a rodding out - I would suspect the pump.. Probably nobody does it unless they are super nit-picky, or habitually check EVERYTHING like the best engine builders, but you can check the assembled pump clearance with modeling clay and the usual gasket. Pump clearance should be somewhere between .0025-.0040 or so. There is nothing rare about our pumps, so if other stuff doesn't pan out, and ya don't wanna do the clay check, just slap another pump on in case the one you got was bad..

And, it might be a good idea to get a gauge or a scan tool of some sort. I payed $14 at Advance Auto Parts for a cheap mechanical SunPro gauge that is MORE accurate than my expensive VDO, and Autometer electric gauges on other cars.. It just screws into the intake manifold idiot light sensor hole on the passenger side of the intake. You can keep the idiot light by using a tee if you like.

Good luck

Billy
Montgomery Village, MD

[instro84]

could also be the fan clutch my wifes van had a similar problem new clutch fixed it.

[flaboy]

Originally Posted by MaxVO2

Also, since the water pump is new, was it just a generic rebuilt pump? or new unit?

the previous owner had installed the water pump... the reciept says "new water pump" so im assuming its new, not a rbeuilt core or something. If the other simpler solutions dont pan out, i'll try another new pump and see if that solves the problem

Originally Posted by MaxVO2

And, it might be a good idea to get a gauge or a scan tool of some sort.

I'm getting a set of guages for the car, specifically boost, knock (little LED one from caspers), water temp and oil pressure, but It will be a week or 2 before I put them in (have to wait till friday for tha cash to pay for em, and then another few days for shipping time, etc.) And from what I hear Scanmaster doesnt work with the stock 84/85 computers... Once i get my guages and get this overheating thing sorted out, my next step is to upgrdade to the 86/87 computer, at which point i will definitely get a scanmaster.

Originally Posted by instro84

could also be the fan clutch my wifes van had a similar problem new clutch fixed it.

The way i figured it (and please correct me if I'm wrong) the fact that it doesnt overheat when at idle and at lower speeds suggest that the fan is not the problem, since these are the times when the fan is the source of most of the airflow over the rad. If it was a faulty fan, i would assume it would be the other way around, only overheating at low speeds and when idling, but cooling down once i got up to speed and got good airlfow through it. The fact that it only over heats at speed, but is fine otherwise suggests to me its a coolant-flow problem, either from crapped-up radiator, or collapsing hose, or (as i just learned) a pump with improper clearances. Like I said, If I'm wrong, please correct me, but thats my understanding of the coolant system.

Thanks for all the suggestions.. tongiht I'm doing the flush and putting in that cleaning stuff, this weekend im gonna empty that out, flush again, put in nice fresh distilled water, new rad cap, and possibly new lower hose (if mine has no spring inside which i will check tongiht) and see if that clears up the problem. I'll keep everyone updated, since I'm SURE you're on the edge of your seat wondering how my overheating problem is resolving I'm so glad the GN community has resources like this and the other websites. when i had my old GS, the v8buicks.com site was invaluable for learning the ins and out and peculiarities of old-school buicks, and it seems these sites will serve the same purpose for my "modern musclecar".

[Old Buzzard]

A blown head gasket... Just at the leaking point as of now...
Have a rad shop pressure check the system. They can also test the rad to see if exh gas is seeping into the coolant...

[flaboy]

With my luck, thats what it is, and i have this hanging premonition that is the case. I certainly hope its not, but like i said, with my luck.... If it is indeed a head gasket issue, what are some other symptoms that would indicate this is the problem? This weekend I'm putting on a new set of plugs. If there was a head gasket leaking, I'm assuming the plugs on the affected cylinders would be nice and "steam cleaned" looking? So if they all look appropriately dirty and old, does that mean my head gasket is fine, or should I still have a rad. shop pressure test and exhaugst-gas test my system? How much does something like this cost? As i said before, while I will spend whatever I need to keep my car running in a healthy condition, If there is some way to confirm (or rule out) the head gasket leak without spending cash at a rad shop, my wallet would definitely thank me Thanks for all the help so far


Oh, and i checked, the lower rad hose DOES have the little wound metal peice in it, so im guessing its not the hose collapsing.

[Steve Wood]

take the cap off, drain some fluid so you can see the end of the tubes in the core..if they are plugged up..it is new radiator time...cleaner seldom does any good.

Also, drive the car and get it hot..then, feel the bottom of the core, is it as hot as the top of the core? If it is relatively cold in comparison, then the core is plugged up at the bottom...my experience is that the bottom plugs first...others may differ?

[JohnLarkin]

Advance Auto sells a brand new radiator for $90. I would be suspicious that the car has been overheating for some time being that the previous owner replaced pump & 'stat with no cure. As for checking for the blown head gasket, rent a pressure tester from the parts store (sometimes free). It goes on where the radiator cap goes and you pump it up like a beer keg. Then you can look for leaks or bubbles, perhaps around the head. How does the oil look? Any milkiness? Residue under the oil fill cap?

[flaboy]

I had the same thought about the previous owner knowing about the overheating problem... If i cant figure it out soon, I may ask him what the deal is.... at this point I dont really care about getting any money back from him or anything, I just want extra info to help figure this thing out. There doesnt seem to be any oil in teh water, or water in the oil, which is good, neither of them seem to be mixing. The rad actually looks pretty new and clean, I doubt it is the problem. I'm just doing this flush and clean on the off chance it is, since it would be a cheap answer, and it cant realy hurt to try If i pressure tested it, and there was a headgasket leak, is it possible the leak would be on an interior part of the head gasket, so i would see no bubbles? granted, Id see the pressure leaking down, which would tell me I had a leak, but it wouldnt neccesarily help narrow down where I guess. The way it looks now, on Friday I'll dump out this cleaning stuff, flush and system to get it and all the loosened up crud out, and do the plugs. If they look suspicious, I'll probably take to a rad shop (damn I hate spending money) to test for exhaust gasses in my coolant and pressure test, unless you guys can come up with a better way of confirming/ruling-out the headgasket leak issue. Hopefully this can all be resolved easily

[Old Buzzard]

1. Do a leakdown test. If the gasket is toast, it may allow air to bubble back thru the rad.
2. Could be the stat is in backwards, but I'd look at what Steve said, about the rad being plugged. The symptoms of over heating at sustained high speed, may indicate that he's right. When around town, and the BTU rejection requirement is low, the rad has enough core exposure to work.. Hiway speeds, and the higher rpms, it doesn't.
3. Take it out, get it hot, and let it cool down overnite, or for at least several hours, then look at the plugs. Smell/taste like antifreeze??
IMO, if the car had no supplemental gauges, nor a scanner of some sort, I'd be willing to bet the previous owner had no clues.. He/she only ran the $hit out of it, and then you inherited the mess.

Bottom line numbers: The system should work, so that the op temp of the engine is approximately ambient + 100*, or if those total to less than stat value, then the stat is the target, +/- 5*.

Look for a temp drop from top to bottom tank of approx 20-30*. NE of your buds have a infrared gun? Shoot the hoses, etc.. and see WTF you have.

[JohnLarkin]

Taste? He's not making moonshine Chuck.

[flaboy]

Originally Posted by Steve Wood

take the cap off, drain some fluid so you can see the end of the tubes in the core..if they are plugged up..it is new radiator time...cleaner seldom does any good.

Also, drive the car and get it hot..then, feel the bottom of the core, is it as hot as the top of the core? If it is relatively cold in comparison, then the core is plugged up at the bottom...my experience is that the bottom plugs first...others may differ?

Mr. Wood sir, methinks you are a genius After reading your post, I have been meaning to check the rad as you suggested, but every day when I get to work I dont have the time before going and clocking in, and on the way home, once i pull up at the house, the only thing on my mind is a cold beer and TV, so i kept forgetting. But not today. As soon as i pulled up at the house, i pulled off the upper shroud, and felt my rad. The top of the rad was toasty-warm.. could only hold my hand on for a few seconds. But the bottom of it was literally cold... not even the slightest bit warm. After some further exploring, it seems the bottom 2/3 of the radiator was cold, no warmth to it at all, and then over the course of 2-3 rows, it transitioned to nice and hot. And this was after a 45 mionute drive home, with all but the first 5 and last 5 on the interstate crusing at about 65. Today was a little cool (for florida) at about 65 I'd guess, but all things considered, I would imagine a healthy non-plugged radiator should have been warm all over after that drive. The surprising thing is, the rad itself looks in great shape, the outside looks very clean and not beat up at all, and when looking inside the spout, none of the tubes i can see have anything near the amount of deposits or scaling I would expect on a 20yr old car, so I had sort of assumed it was in pretty good shape.

So this weekend I'm going to pull it out and take it to a rad. shop in town to ahve it rodded out and cleaned, etc. I know now would be a great time to drop in a F-body rad an electric fans nd all that, and while that is in the plans at some point, for now I'm just goin with the bare minimum i can afford. If that doesnt seem to solve the problem, I'll probably start exploring the head-gasket leak possibility. Thanks so far for all your help guys, and I'll let you know how it comes out! and once again steve, thanks for your suggestion... man, having these support web-sites is such a life-saver