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Post Info TOPIC: Thermostat all over the place


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Thermostat all over the place
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I purchased my '68 Biscayne a few weeks ago and in the little driving I've done I noticed the thermostat is all over the place.  Not cool at all (pardon the pun)!

The engine is a non-original 454 BB.  Supposedly the engine puts our 400 horses, but I have no idea if that's factual.  The 10-bolt rear end seems mismatched with that type of power (Thanks to Pat for that learning point).

I've driven the vehicle about 50 miles most of which was done on the highway at around 60 mph.  At no point was I getting into it and I don't think I ever put it over 2500 rpms.  For the most part I was cruising at 2200 rpms behind my girlfriend in the slow lane.  In retrospect, I wish I had gotten it towed home..

Before going anywhere I checked the coolant level.  The overflow was nearly empty and the coolant was several inches below the radiator cap.  I went ahead a filled the overflow mid-way and then filled the radiator to the cap.  While driving the temp seem to stay around ~195 after warming up, but from time to time it would jump up to 220 and even 230.  The odd part was that these were spikes that happened in a matter of seconds.  I'd be running at 195 and then in the matter of 5 seconds it would quickly climb to 220/230 and then a few seconds later it would be back down to 200 and then a few more seconds later it would be back to 195.  At one point (a fairly scary point) the thermostat jumped all the way off the end >250 at which time I immediately pulled over and shut it down.  Again, within 20-30 seconds I was back at 200.

Upon further inspection this past weekend I noticed a bit of coolant sitting on top of the head.  I start it up and within a few minutes I notice a leak coming from the temperature sender (I think that's the correct name) screwed into the header.

Here are my general questions:

1.  How do I proceed with diagnosing this problem?  The sender and thermostat looks new, but it's obviously loose.  Any idea how tightly this thing should be torqued?

2. What temperature should I be running at once warmed and what temperature thermostat (e.g., 180, 190, 195) should I be using?

3. Could this be a problem with having an air pocket in the system?  If so, what is the right way to bleed air or how do I burp the system?

4. What brand/type of radiator fluid should I be using?  At minimum I assume I'll be flushing the system.  In that case, I'm fine with replacing the thermostat and/or temp sender.

5.  Should I purchase a shroud and if so where can I get one that looks reasonably original?

Sorry for the rather long post.  I have much to learn!

Pictures attached for additional context.

 Chad



-- Edited by Chad on Wednesday 16th of November 2016 10:38:08 PM



-- Edited by Chad on Wednesday 16th of November 2016 10:39:27 PM

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I would.....start over with reassurance that everything is done correctly......before you drain the coolant do the following.

1, Get yourself or rent a pressure tester to determine if any leaks. Sounds like you obviously have a leak problem.
2, Replace the thermostat with a new 160-180 is what I recommend.
3, Replace all the antifreeze with 50/50 mixture.
4, You apparently have an overflow bottle....your car never came with an overflow bottle. You just have to decide on whether or not to use one? These radiator's were designed to run at a certain level, if you overfilled it.....the coolant would escape through the overflow hose.

This should be a good start in the right direction.

Dan

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OK, since your are new to the car hobby, let's start with a little terminology so that our communication is accurate. The gauge that indicates engine temperature is called a "temperature gauge", not a thermostat. The thermostat is a different component of the cooling system. The part of the engine that your temperature sending unit is screwed into is the "intake manifold." Your thermostat is also in the intake manifold under/inside the thermostat housing which is the part on the engine that your upper radiator hose is connected to. The thermostat opens and closes according to the engines temperature. When it is closed, coolant is blocked from circulating through the radiator and only goes through the engine. Once the engine warms up to operating temperature the thermostat senses that and opens up allowing coolant to flow through the radiator which maintains the temperature. The header is part of your exhaust system and is composed of the steel tubes bolted to the side of the engines heads and carries the exhaust down to the exhaust pipes and mufflers. Headers are an aftermarket modification that replace original cast iron exhaust manifolds for improved performance.

I would follow Dan's recommendations, starting fresh with a new thermostat and coolant is a great idea. I would also suggest you replace that universal upper radiator hose with a molded hose. You can reduce the chance of leaks around the sender by applying some sealer when you screw the fittings in. You mentioned while we are chatting that you are taking classes at the local community college on auto repair. That is a great place to start, though I expect the emphasis there will be on more modern cars. The basic theory and components are the same. Another great source of education is to find a local car club. I am sure there are several in your area. Start by going to car shows and talking to people and ask about clubs. You can actually kind of "shop" for a club with interests similar to yours. They are often aligned by types of cars, street rods, antique, muscle cars, modern muscle cars, tuners etc, or by brand or models like a Chevy, Ford, Studebaker or Mopar club, or Camaro, Chevelle, Impala, Mustang, Corvette, etc. Find one that seems like the best fit for you. Also look at what sort of activities they do. Folks in car clubs often have a wealth of knowledge and can help you learn or will even pitch in and help on projects. A word of caution though, some folks who think they have a lot of knowledge really don't so don't trust everything your hear.

Now, about your cooling system, your car is similar to mine when I got it. Chevrolet changed their design between the 1968 and 69 model years and went from the short water pump design in 68 to the long water pump design in 69. When they did that, they also moved the alternator from the driver side to the passenger side. Your car appears to have the later model set up. It will function just fine but is not "correct" for your year. That makes finding a radiator shroud that will fit a little bit more challenging. There is good chance that a radiator shroud from a '69-70 car would fit. Finding the right one becomes more challenging. They make different ones for small block and big block, for cars with or without AC and even for cars with automatic transmissions. Some also attach to the radiator differently, either with bolts or with clips. This is part of the challenge and the fun of this hobby, finding just the right parts. You can do like I did and convert it back to the correct '68 configurations, but it is not as easy as it sounds and it is not cheap. You will have to change the water pump, all the pulleys, the alternator and power steering mount brackets and even the power steering pump. You can find original parts, but often they are very expensive due to rarity or you can use "repop" pieces. The danger with that is some do not fit as they should. I am not trying to discourage you, just wanting you to understand. You can see how I did my conversion by looking through the pictures at the links in my signature.

I hope this rather long response is helpful, I hope I did not start at too basic a level. Don't hesitate to ask questions.

Pat



-- Edited by Pat Dilling on Thursday 17th of November 2016 09:22:57 AM

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http://twodoorpost.activeboard.com/t59692612/my-68-biscayne-as-i-received-it-and-recent-fixes-and-upgrade/



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Thanks for the replies, Dan and Pat. I've already started looking for a pressure tester. I also went back and looked at my GM Shop Manual to learn a little more about my radiator. If I'm reading the document correctly the coolant level should be 1 inch below the filler neck when cold (assuming I don't have a crossflow radiator; in that case it would be 3 inches below the neck). I was also wondering what was up with the cheap plastic overflow bottle.. thanks for enlightening me, Dan.

Thanks for clarifying the terminology, Pat. This is incredibly important when asking questions and it's safe to assume I have minimal or no knowledge; I certainly don't feel like you're talking down to me or anything.

Yes, I'm taking courses at the local community college to get my feet wet in a structure environment. Currently, I'm enrolled in engine repair. The course covers topics such as engine compression testing, use of micrometer, basic engine components, valve testing a replacement, determining when a block is good or bad and when it can be sent to a machine shop, etc. Basically, we've just be tearing down an engine (2003 Honda hybrid - 1.4L - inline 4 cylinder - it's sad), measuring and next week we'll begin putting it all back together. Beyond this course I have no real hands on experience. Thus, I've very grateful for everyone's support and suggestions. Next semester is brakes and steering/suspension.

Next steps are to:
1. Apply sealer to the temperature sender to address the know leak. (Any suggestions on the type of thread sealer?)
2. Find a compression tester and test the system (and hope I don't find any more leaks).
3. Assuming #2 goes well, look into replacing the thermostat. I assume it would be wise to also back flush the system before replacing the fluid with the 50/50 mix.

Once that's done I can look into replacing the upper radiator hose.  I do see some corrosion on the other coolant lines, so it might be a good idea to replace those as well.  I'll have to do some additional investigating on the conversion you suggest, Pat. I'm guessing that may be over my head for the time being, but I'm certainly willing to learn. I'll also look into the local clubs. My girlfriend and I have already attended a few of the local shows and I'm very interesting in making new friends. Thanks all!!



-- Edited by Chad on Thursday 17th of November 2016 10:42:46 AM



-- Edited by Chad on Thursday 17th of November 2016 10:43:21 AM

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Would loctite be good for this application?



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Hi Chad, no on locktite. You can use Teflon tape or they also sell thread sealer that is Teflon based in a squeeze tube.




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Thanks for the advice, Kevin.

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You might check with your auto class instructor to see if the school has a coolant system pressure testing device (not a compression tester, that is something different). He/she might eve take it as an opportunity to demonstrate how to use one to the class. You can also check at your local auto parts store like O'Reilly, Advance etc. They often have specialty tools to loan. They charge your card then remove the charge when you bring the tool back. Your radiator is a down flow, tanks on top and bottom, and the coolant flows vertically from top to bottom. A cross flow has the tanks on either side and the coolant flows horizontally from side to side.

Keep asking questions

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One of the first things we did in class was an engine compression test. Unfortunately, we only discussed the coolant system pressure testing in passing and I learned a little in my reading. Also, I called my local AutoZone and they'll let me borrow a tester for 30 days at no charge with a $75 refundable deposit. Once I have the unit in hand I'm sure I'll have lots of follow up questions. Thanks, Pat.

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There should be instructions with the tester, also check Youtube. Lots of how to stuff on Youtube, but see if you can find a couple to look at. I have seen some real shade tree methods that I would never do filmed and shared.

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Hey Chad, my 2 cents on cooling mystery.

1. Sometimes if the engine has been totally drained of coolant and then refilled it can actually develop an air pocket.

   If that be the case you might try draining about a gallon of coolant from lower radiator hose and refilling.

2. Is the alternator/ water pump belt in line?

   May be an optical illusion just looks like the belt should be on back groove.

Good luck and keep the guys posted on your progress.



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Thanks for the suggestions, Jerry. My first thought was an air pocket as well. I'll have to follow up on this once I've verified all the leaks have been address.

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I got the coolant system pressure tester this weekend from Autozone. After bringing the system up to around 14 psi I immediately noticed a leak in the upper radiator hose (at the end connecting to the intake manifold). After addressing that issue I still have the small leak coming from the temperature sender. Otherwise, I didn't see any other leaks and the pressure seems to hold on the tester. Unfortunately, I haven't had a chance to address the 2nd leak. Will keep everyone posted. Many thanks for all the suggestions.

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Good job! I bet a little sealant or teflon tape around that fitting will solve that problem. For burping the air out of a coolant system I have been using this funnel system. Best thing to do is raise the front of the car while you are doing it. It's a good tool to have for any car you might work on.

https://www.summitracing.com/parts/lil-24680/overview/

Pat



-- Edited by Pat Dilling on Monday 21st of November 2016 10:20:22 AM

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Actually, I have that very same part I bought to do a job on my primary vehicle. The reason I didn't fix the temp sender yet is because I still need to dispose of the coolant from the previous job.. :) Thanks for the tip about raising the front end, Pat. You guys are awesome!

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Quick update. Drained coolant and popped out the thermostat. It's a 195. I warmed up some water to around 195 in a pot and then dipped the thermostat in using some string.. I then slowly turned up the heat to boiling ~212 and it opened up, but not a lot. Unfortunately, I don't have a known good thermostat to compare it against, so I can only conclude it's at least working in part. It may also require more heat to fully open, but 212 is the best I can do in a pot.. Tomorrow I'm planning on getting a 180 thermostat, applying sealant to the temp sender and then refilling with 50/50 mix.

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Good plan, keep us posted.

Dan

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Chad wrote:

Quick update. Drained coolant and popped out the thermostat. It's a 195. I warmed up some water to around 195 in a pot and then dipped the thermostat in using some string.. I then slowly turned up the heat to boiling ~212 and it opened up, but not a lot. Unfortunately, I don't have a known good thermostat to compare it against, so I can only conclude it's at least working in part. It may also require more heat to fully open, but 212 is the best I can do in a pot.. Tomorrow I'm planning on getting a 180 thermostat, applying sealant to the temp sender and then refilling with 50/50 mix.


 Chad, Also as a footnote...There are 2 plugs (with square heads) under the engine mounts, just an inch or so above the sides of the oil pan. If you remove them (with a catch pan under the engine), you can completely empty the engine block of coolant. Many times, the holes are plugged with sediment, and may need to be poked thru with a screwdriver or the like, to successfully drain the engine.



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Not to dissuade or hijack, assume etc...( Im married for 30yrs so ive learned to add in my disclaimers...) how does the car run when you put your foot in it? I ask because you purchased this car and the seller installed the engine etc? Correct? Another thing to look for would be timing...too much advance would also cause it to run hot. As for your thermostat although the engine isnt original- possibly sticking as close to the oem t-stat temp as possible would be best. To cool and the engine isnt as effective at operating effectively and also too cool prevents the engine from getting rid of carbon, gassing out the acidic by products of combustion over time. All this is probably TMI but the majority of engines on the road dont need a lwr temp t-stat ...then again what u are fixing already is the right place to start. My interpretation of the heat cycle u wrote about was your t-stat opening and closing but w each cycle increasing in temp...eventually it would just continue to climb in temp...symptomatic of cooling system and maybe also the too much advance on ignition timing. Not knowing how the car runs...figured id toss it out there. Not trying to make you worry about other things..just had all this useless info stuck in my head that had to get out!!lol Good Luck and still a schweet car!

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The good news is after fixing all the leaks and installing a new 180 thermostat it appears the engine is running cooler and the temperature is a more stable (i.e., not jumping all over the place). I want to say burping the system was beneficial. The drained coolant didn't really look that bad. My testing was on a 55 degree day and I only ran it for a few miles (after letting it warm up in the drive way), so this should be taken with a grain of slat. Part of me is interested in testing with a new 195 thermostat to see if I have the same stability, but I'm going to save that fur another day.

Thanks everyone for the advice. On to the next topic. :D

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