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Discussion Starter #1
Here we go. My wife blew the motor in her 98 Oldsmobile intrigue, so i swapped the motors, and it wanted to run hot only on the highway with AC on. City driving, AC on or off, is fine, but highway AC on it gets hot. So, i replaced headgaskets, lower intake Mani gasket and new Plenum. Replaced all necessary gaskets to do so. I have no check engine lights on. Just a low coolant light. I know that sensor is bad, but shouldn't have anything to do with temp. It holds all fluids, no leaks, and no coolant in the oil. Could it be afaulty water pump? Faulty temp sensor? And if so, how can i check before replacing any unnecessary parts. Maybe it's something else that I'm missing? But it seems to have solid flow through both radiator hoses.... I'm stumped
 

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Discussion Starter #3
That was my first thought. So naturally, i removed the stat entirely, and that's how it is now. I put a new 180 in it, and thought maybe it was faulty. But even without a tstat it still runs high
 

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Discussion Starter #4
Could i have a timing issue? Maybe a tooth off? But it runs as smooth as ever with no sputter or hesitation whatsoever.
 

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No a timing issue wouldn't cause that, my next thought is are both your cooling fans working properly? Also how do you know it's getting hot? Could be a bad temp sensor (below the thermostat in the LIM)
 

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Discussion Starter #6
When AC is turned on, both fans kick on. And they both kick on once the temp gauge reads a little over halfway. I assume that's correct. I've read that if the temp sensor is bad, that it could cause the fans to come on incorrectly. Idk how true it is. And i assumed its overheating because once i hit the freeway and AC on, the temp gauge just climbs. It gets halfway between half and 3/4 before i kick off the AC.then it drop back down to 1/2. I'm so lost
 

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hmm.. when was the last time you had a rad flush done? Is the cap & neck covered in scum? Sounds like your fans are working properly and so is the temp sensor. Last thing I can think of is the extra strain from the AC compressor is simply overloading a gunked up rad.
 

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Discussion Starter #8
I'm gonna take it to have a pressure flush done today. I hope that does it. I wanna make sure if I'm doing it, it gets done to the best ability with as much force as possible, that way I'm not wasting money on coolant, to not get it all out. Ill let you know the outcome. Pepboys is gonna test the cap first
 

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I was concerned of running too hot last summer. I heard that Harley motorcycle guys use Royal Purple because it drops the temps. I switched to Royal Purple and Lucas oil stabilizer. I dropped my temp at least 20 degrees.
I am not promoting or selling Royal Purple. I was seriously considering a larger radiator.......hope this helps KEV
 

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Discussion Starter #10
I thought about a larger radiator too, but there has to be something causing this issue. And if it doesn't get fixed now, i think it'll only get worse. I run Mobil synthetics in all my cars, and they seem to really like it. I did aswell when replacing the head gaskets, i enlarged the coolant port hole, because the difference between coolaant jackets, and the hole in the gaskets, were so dramatically smaller. Every tech i talked to said its only gonna cause more coolant flow which is what i want. And it would run cooler. I only opened it to about 5/16" opposed to the pen tip sized hole that was there. And when i removed the originals, those tiny little holes had about 1/2" THICK gunk on each side. I'm wondering if someone tried putting in some coolant stop leak or bull**** in the motor before i bought it.
 

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Are you talking about the coolant end cap under the throttle body? There was a writeup a while back about doing that and the pros/cons. I can't remember what the ideal size was but there was such a thing as too big. The reasons why it's done (in case you were wondering) is to get more coolant flow to the back head as it runs hotter than the front because it doesn't get the same air flow. Ideally the front & back heads should run at the same temp but that's not the case.
 

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I previously had been running Mobil 1. If you do not have a flow restriction,
you might get by. I am now running Royal Purple max cycle oil for my lawn mower and small 4 cycle blowers, etc. On a small engine forum, a small engine shop mechanic check the difference using a heat gun and said it was almost 20 degrees difference. Just a thought. Good Luck ......KEV
 

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Discussion Starter #13
No i left that coolant cap alone. I replaced the gasket, because it came with the head gasket kit, but i didn't drill that. I drilled the head gasket itself, because the coolant flow through it, was so restricted
 

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Discussion Starter #14
Everything is "operating normally".but still overheats. Could i have gunked up passageways internally in the block? Or what if its that stop leak s***? Is there anyway to get that out? Would a flush do it? I didn't wanna have them flush it, and waste anymore money. I'm stuck as to what i can do, without replacing the engine, again.
 

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I am currently flushing out my system. To avoid having to add hard chlorinated city water, I do the following:

1) Drain system, pull lower rad hose and use shop vac to remove as much as possible. You should be able to remove about 8 L of the 12 L in the system. The shop vac will help remove some of the sludge in the lower block without having to remove knock sensors, although you may have to go that route.

2) Add 1/2 L of distilled water through the thermostat housing, vacuum out. Repeat until water is clear.

3) Fill system with distilled water, install radiator cap so system will be pressurized. (Water boils at 100°C unless it is pressurized. Pressurization alone increases the boiling point of water, adding coolant further increases the boiling point). Use some kind of scanguage to monitor the water temperature.

4) Drain and assess the coolant. Repeat steps 1-3 if necessary.
 

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How does your radiator look?

I, personally, don't like to add anything to my cooling system other than distilled water and coolant. I guess there are times when a chemical flush is necessary. I've never gotten to that point, however. If my radiator was so bad it needed a chemical flush, I'd be tempted to replace the radiator.

I don't believe you ever told us what temperature your coolant is getting up to yet. If you have a scanguage, plug it in and get a reading for us.
 

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Discussion Starter #18
I don't have a scangauge. But my temp gauge on the dash is reading as high as 3/4 on the gauge. I try not to let it get that high due to overheating and doing internal damage. But I'm not sure of the exact degree. But when i pop the hood, it gets HOT. Hotter than my 99 regal with the same powerplant. Mu radiator appears fine. I have all cooling fins and no damage to any of it. I'm thinking i may have a coolant blockage in the head or block somewhere. Before i replaced the motor, the temp gauge always read right on 1/2 until she blew it due to running it dry after leak occurred. I just want it back to normal lol
 

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Discussion Starter #19
Hmmm ok, so i believe i figured out the overheating. I noticed today, while ensuring there was no air in the system. That my lower radiator hose is actually collapsing about 2000+ rpm's. I've had that lower hose off multiple times and probably weakened it. With it collapsing, I'm not getting flow, therefore overheating. Does anyone know where i can find a lower hose with a inner spring? To prevent this from happening? And could this be happening because i bored out the coolant jackets on the head gasket? Allowing more flow, and its pulling to much?
 

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Is it very soft to squeeze? You could get some braided stainless hose or they make these coils that slip over hose for tight bends but I'm not sure if they get that big. Your best bet would just get a replacement factory hose and see if it collapses too.
 
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