UPDATE!! Running too hot, but not as much as I thought

[Guest bastaad525]

I thought I had licked this problem. A couple weeks ago I posted that my turbo Z was running a bit hotter after replacing the head gasket, and a bit too hot overall if the stock gauge is to be trusted as accurate. I believe it is probably pretty accurate...

 

I have a 180* thermostat installed, and when I start the car and just let it warm up idling, it will get up to the halfway mark (actually just a tad above) and stop. It will stay right there no matter how long I leave it idling, so I assume that the midpoint on the gauge is about 180* Does this make sense? Or does the gauge stopping necessarily mean that the thermostat is fully open? I really want to get a real thermostat and verify what the guage is telling me.

 

lately it's been pretty cool here in SoCal, especially at night/early morning, which is when I drive to and from work (graveyard shift) and the temps have been pretty good, never getting more that a needles width above the midway point.

 

Today I was out and about well into the afternoon, and it was a bit warmer today than it's been lately. Up on the freeway, just cruising at about 75, the temp gauge got up to about 2/3. It would fluctuate a little back and forth, and even if I got on it for brief spurts, it wouldn't go any further than that, but to me that is too warm. I dont think I ever saw it get that warm before I replaced the head gasket, and I dont know what might have happened when I changed the gasket to cause this to happen.

 

I am running the 280zxt radiator, and it's in good shape. I have recently (within the last six months) replaced the radiator cap, water pump, thermostat, and all coolant hoses. The fan clutch is working fine, and I am using the zx fan shroud.

 

I noticed this happen a few weeks ago and posted about it and some guys suggested I might have air bubbles trapped in the coolant system. I followed Tim240z's directions for how to purge any air, and it seemed to work. I had to replace the lower radiator hose a couple days ago... though the hose was new, it decided to commit suicide by getting into a fight with the front of the alternator. After draining the coolant, replacing the hose, flushing the system, and refilling with new coolant, I repeated the procedure for getting the air out of the system. So as far as I know, I shouldn't have any air bubbles in there. When I had the head off to replace the gasket, all the coolant passages looked pretty clean, no big clogs or restrictions that I could see.

 

So I'm at a loss. Everything appears to be in good order.... so why else could it be running so hot? As long as it seems stable as it has been, and isn't continuosly rising, should I worry?

[Jersey]

Two quick things come to mind 525 - you say you replaced the thermostat - was it a Nissan one or an aftermarket? I found the aftermarkets not to be as "flowing" as the OEM one because of the hole opening diameter. Also, if you have a meat thermometer, stick it in your radiator after she comes up to temp to verify if the temp sensor and/or gauge is off. I just went through this a few nights ago on my cousins car - sensor was on the hot side by about 40deg Pulled the only hair i had left out before trying something easy as it turned out to be.

[fl327]

Had the same issue with the temp being a little high sometimes (a hair over the middle of temp guage) and went through much the same troubleshooting, until I went to a Nissan themo, and now it stays right in the middle and right below the middle on the freeway. Even went with the nissan oil filter, good parts. Of course me being me I went schizo on the whole situation so it may not be the same result. I went and added another electric fan that cycles on and off from 190-185 and added the temp switch to my other electric fan so that it comes on at 180 and shuts off. 16" in front 10 in back of the radiator, I get hot now I know somethings up

[Guest bastaad525]

Yep it's an aftermarket T-stat. Man you never know which parts you can get away with getting aftermarket, and which ones you really need dealer parts... and I never understand why dealers charge so damn much even if their parts are better, the prices just dont seem justified.

 

Heheh sorry for that little rant. This is another case of my turbo motor seeming more 'sensitive' than any other car I've had. I've never had problems using common auto zone parts before, but with this turbo setup man for some reason it just does NOT like aftermarket anything. Stuff like three aftermarket alternators blown in less than 2 mos. Install the Nissan, and it's been fine ever since. A blown aftermarket headgasket. Several leaky aftermarket valve cover and manifold gaskets, and one leaky aftermarket water pump gasket. Aftermarket lower radiator hose that decided to change shapes spontaneously one day. And now the T-stat. I just wish I had the money to always buy the Nissan stuff. Well on top of that a lot of this stuff they dont have and either can't get or take forever to get. I dont go out of my way to get the cheapest stuff either... whenever I go to auto zone or napa I usually spring for whatever the most expensive option is if there is one.

 

Anyways, thanks for the tip guys, I never even thought that would be an issue. I still find it strange that this only happened after I replaced my blown gasket, but I'll try the Nissan t-stat and see what happens. I was going to borrow a meat thermometer to check the temp but I can't leave the cap off long enough to really check it. Once the t-stat opens and the coolant gets close to normal temp it will start overflowing quickly. Or do you mean I should stick the thermometer in the fins or something like that?

 

Lastly, have any of you guys tried Redline Water Wetter? I heard or read somewhere that this increases the effectiveness of regular coolant and will help the car run colder, but then one place I called that carried it said that it was more just for keeping the radiator free of corrosion. Should I pick some of this stuff up?

[Tim240z]

Did you repurge your cooling system after the hose replacement?

[Guest bastaad525]

yeah did the exact same procedure after replacing the hose... To be honest I dont think it made a difference the first time I tried to purge the air bubbles either. I think it was just running cooler because it had been relatively so much cooler outside after I did that, especially at night. Even last night and this morning the car ran where it usually does, right around the middle. It was only yesterday when it got a bit warmer and I was driving in the afternoon that it started to really get too warm for my liking. I haven't really driven the car in the daytime for a long while... rather like taking the wifes 'new' Geo with AC and CD player

[fl327]

You may have too much antifreeze to water ratio.

California weather doesnt require so much antifreeze, doesnt get cold enough I guess. I run about 30 percent antifreeze and the rest water, antifreeze really just for anti corrosion and lubrication of water pump.

[Jersey]

Two other things i just thought about - Make sure your timing is correct. I think you're running the '81zxt L28 and it should be 20btdc. This should be checked after the motor's warmed up and the ECM is taking readings from all the sensors, including the TPS. I remember you mentioning something fishy going on with your TPS, just check to make sure at idle (i believe set @ 700rpm for manual trans) the TPS is pulsing the injectors at the slower rate and the motor hasn't run at idle for too long... just in case it's running rich or something and throws the ECM into default mode, then you'll never get correct timing @ idle. The other thought was - maybe it's running a little lean. This could cause it to run a bit hot as well. Unfortunatly, leaness could be caused by a bunch of things - dirty injectors, TPS, HTS, AFM, FPR, partailly clogged fuel lines, pump... well, i'm sure you know what i mean. Did you do a compression check before and after the last head gasket re-build? Wonder how much they shaved off to get a clean surface. This would raise compression a little as well. Just thinking out loud. Keep us posted.

[Guest bastaad525]

fl327 - I've experimented with this as well. I usually run 50/50, but when this problem first started I did drain out a bit of the mixture and replace with just straight water to increase the water to coolant ratio. It takes me about 2 gallons to fill the thing completely, I started with one gallon of each. I then drained approx 3/4 gallon and replaced with straight water... I dont know what the ratio would be at that point my math is kinda rusty. At any rate, it didn't make a difference.

 

Jersey - yeah there's still something fishy going on with my TPS. If I leave it connected, there is a very noticeable stumble, like a hiccup, every time the TPS goes 'open'. Also, it affects the timing oddly. With the TPS connected, at idle, I have my timing set a little retarded (18* BTDC) just as some added insurance against detonation. Now, watching the timing, as soon as you touch the throttle and that TPS goes open, the timing instantly jumps down to about 12-14*. After that, as the revs are brought up the timing slowly advances as it's supposed to do. I've asked about this but didn't really get any good ideas what might be causing this. One person (yo2001 I think) suggested this is actually what it's supposed to do, but it doesnt seem right to me and I think the timing jumping like that is the cause of the stumble. The TPS unit itself is working properly (it really just functions as an on off switch) and is adjust properly (it goes open with just the slightest touch on the throttle). So I got tired of it and disconnected it again. Even when I had it connected for like a week it didn't affect temps at all.

 

The engine definately runs a little on the rich side most of the time. I can't say if it's running rich or lean in any individual cylinders due to dirty injectors or what not, but my combined air/fuel ratios were good when i was on the dyno. The only time it ran lean was at WOT past about 5000rpm. I dont drive like that very much on the freeway so I dont think that's it either. Matter of fact the odd thing is if I push it, it will run cooler while I'm pushing it, until I let off and go back to driving 'slow'. I did not do a compression test after the gasket replacement. The machine shop guy did say that it was only very slightly warped and he only needed to shave a very small amount to even it back out.

 

I'm putting my money on it being the t-stat. Okay well I'm hoping that's what it is anyways

[Guest bastaad525]

okay I bought a 0-220* meat thermometer, the kind that's just like a long needle with the gauge at the top.

 

I have a quick question, where is the best place to stick this thing to get an accurate reading and verify how accurate my temp gauge is?

[Guest bastaad525]

Well I must be one of the lucky ones

 

Turns out my 240's temp gauge isn't really too far off afterall. Was really hoping that was the problem. Anyways I got the meat thermometer, and tested it against some other thermometers I had in the house and IT is definately pretty spot on as well. Drove the car to work and popped off the radiator cap and stuck it in there. Did it again on the way home. With the temp gauge right in the middle (about 185*) the thermometer read 170*, so only about 15* discrepancy, assuming it's always off by about the same amount... I'll do more checking to try to verify that.

 

Well knowing that puts me a little at ease at least. So the motor is usually actually running at about 170-175 on cooler days/nights, and is getting up to about 190 when it's warm out or when I push it, and the highest I've seen is about 195, which it got to the other day when it was both warm out and I was stuck in bad traffic on the 101. Now that I know how far off the gauge is I'll definately be picking up a Nissan thermostat soon. I still find it odd though that it tends to run warmer when cruising around 75-85mph on the freeway, whereas stop and go street traffic it runs just right... every car I've had with overheating problems ran hotter on the street and always cooled down on the freeway.

 

Another interesting thing I learned today... yet ANOTHER case of my car mysteriously fixing something on it's own... sorta. Decided to check the timing today just to be sure it hadn't adjusted itself. Well I forgot to hook the TPS back up... I always adjust it to my desired number (18* BTDC) with the TPS hooked up... this is how I"m supposed to do it right? Well with the TPS disconnected it read about 22*... then I remembered to hook it up and yeah it was right where I set it still at 18*.

 

This is odd... as I responded to Jersey in this thread it used to go way retarded by about 6-8* whenever the TPS would be disconnected or go to it's open/off idle state, and then start to advance normally. So now it's doing just about exactly what it's supposed to do. Though, there is still that slight hiccup whenever the TPS goes open... odd.

[Guest bastaad525]

Now that I know what temp it's really getting too (195-200 degs tops so far, average around 185*) should I still be worried? What if I replace the t-stat with a nissan unit and it still gets that warm? Kinda leaves me out of options. The only other thing I can think to try is to have the radiator flushed and cleaned. A better radiator is NOT an option right now.

 

Am I risking damaging anything, warping the head or anything at 200*? I know the car doesn't run as well at that point... well not noticeably really except I can hear the valves are tapping louder and the idle is just the slightest bit lumpier. I just have this very strong feeling that replacing the T-stat is NOT going to fix this, and wonder how much further I really need to go or how much it really matters that I stop at nothing to fix this?

[wheelman]

Bastaad525,

When was the last time the cooling system was flushed? I have a Ford Ranger pickup that acted the same way your car is acting. I ended up having to replace the radiator and flush the block to correct it. Not what you wanted to hear but maybe a simple flush will fix it.

 

As for it running hotter when on the freeway than in traffic, could it be that on the highway your on boost and the engine is working harder than it is when in traffic? If the radiator is slightly plugged or a passage in the block or head is obstructed it might do that. Are you sure no gasket material got into one of the cooling passages in the head when the gasket blew?

 

I'm no expert but I would think that running at 200* won't hurt your engine. If I remember correctly most newer engines run hotter to reduce emissions and aluminum is used as head, block and piston material in a lot of them.

 

Running rough at higher temps could simply be that the ignition has been retarded to reduce pre-ignition or the engine is on the verge of ping and just doesn't burn the fuel as efficiently. I'm just guessing so don't put to much credence in what I'm saying.

 

Anyway if I were you I would flush the radiator and then continue to keep an eye on it if the temps are still high.

 

Wheelman

[Guest bastaad525]

It just seems odd to me... every car I've had that's ever had ANY kind of cooling system problems ALWAYS ran hotter in traffic and would cool off once I got up to speed. Today once again the car was running hotter doing 75 on the freeway and once I got on the street it cooled down. It was a relatively cool day out, about 10am, I'm guessing about 65*, and on the freeway the temp hovered around 190ish. I'm not on boost at all on the freeway, when I'm cruising along I'm usually running about 10hg's of vacuum or so. I definately boost more on the streets taking off from light after light

 

Well I definately want to swap out this el cheapo auto zone t-stat for a good nissan one and if that doesn't help then yeah I'll definately look at flushing the cooling system next as it's the only other thing I can really do other than going with a better radiator or installing a second fan or something like that. thanks for the tip dude.

 

So no one on here has tried Redline Water Wetter and can say if it helps to run cooler or not?

[Tim240z]

Putting on a bigger fan is going to do nothing for you at freeway speeds.

Is your radiator well sealed at the sides? mabe at higher speeds, the air is going around the radiator, instead of through it.

 

Tim

[Jersey]

How about your exhaust 525? Any restriction? Could be the cause of running a bit hotter on the freeway.

 

My TPS and the TPS on the 280 turbo i just built affects the timing exactly like yours is acting - retards a bit when the TPS goes open around 900rpm and then advances as it should when the R's are brought higher. I get the slight hiccup as well in both cars as you do but don't worry about it. Just the way it works i quess. With it disconnected, i think the only affect it would have on your car is at idle, she'll be rich because normally at idle when the TPS is suppose to be closed, it would be pulsing the injectors at a slower rate.

 

If your temp gauge is reading near 15 degrees hotter, i'd put $ on it that its the sender. If i had an extra, i'd send it. Just so happens the 280's sensor was off as well and i used the only spare i had. Should be able to find one for next to nothing from someone here. Probably be a good time to put this sensor in when you do the thermostat, if you do feel like changing it.

[2many280s]

I was just having this same problem, the longer I drove at high speeds (Above 65) the hotter my car would get, but in traffic, or just driving around town at 45ish it never even got up to the halfway point on the temp guage... New thermostat,water pump(needed that anyway old one was starting to leak) good flush of the radiator wich seemed to be flowing well out either hose, same with the engine. But after it pegged the guage on me I decided to pull the radiator and have it checked. The radiator shop did a flow test on it and it was clogged. Took 2 days to get it back because they said it needed to sit in the vat for a couple days, but she runs cool as ever now.

 

Its free for most radiator places to flow test one, can't hurt =)

[Guest bastaad525]

Tim - I'm not really sure what you mean, what am I looking for to see how well sealed it is? A lot of what I've read in the archives here talks about the airflow thru the radiator at speed, I guess it sounds like the 240 was pretty bad for this as well? I thought by running the zx radiator and fan shroud that would help to concentrate the airflow thru the radiator?

 

Jersey - yeah my exhaust is restrictive but no more than stock, i'd guess. Running the stock DP into press bent 2.5" pipe, thru a glasspack and that's it. never heard of that causing warm running the odd thing is I dont really remember it running this warm until after the head gasket blew and I replaced it. Perhaps some gasket material did get stuck in the system somewhere. Thanks for mentioning about the sender (that you'd send me one I mean) but it's alright now that I know how far off it is I'm not really worried about it. What I WOULD like to know is if it is always about 15* off or does it get more off (or less for that matter) as the gauge goes up? Don't think I'll ever find out... unless I do something crazy like pull over on the freeway and check it, because it always goes back down to about halfway by the time I get home. That's good to know that my car isn't the only car that reacts like this to the TPS!!!! Up till now I've made several mentions of this on this board and no one has ever said "hey me too"!!! Well that's one problem that I will finally STOP trying to solve! I figured leaving it disconnected was causing it to run richer at idle... I dont like that idea really, but at the same time I love the throttle response with it disconnected, no hiccup... I'm constantly going back and forth between hooking it up and taking it back off.

 

2man280s - fortunately it doesn't just keep on rising, at least, not so far it hasnt! So far I've seen it get as high as about 200 but it held there. I'm going to be calling some radiator places tommorow just to check and see how much testing and cleaning costs and try to get ahold of a nissan tstat tommorow.

[Tim240z]

Ehh...200* ain't nuttin'.

I wouldn't be concerned....don't chase a problem that really isn't there. I've always used aftermarket thermostats in all my cars...they're fine, and 200* isn't anything special for a max mark.

 

Hell...my LT1s don't even kick on the fan until 220*....different application I know, but......

[Guest bastaad525]

Ehh...200* ain't nuttin'.

I wouldn't be concerned....don't chase a problem that really isn't there. I've always used aftermarket thermostats in all my cars...they're fine' date=' and 200* isn't anything special for a max mark.

 

Hell...my LT1s don't even kick on the fan until 220*....different application I know, but......[/quote']

 

yeah... the more I read the more I think 200 isn't really so bad afterall... I used to always believe that temps were never even supposed to get over the point where the tstat opened... guess that's not really the case. I've also noticed that the V8's seem to run a little warmer on average than the L28 cars.

 

Tim, okay you say 200 is okay for a 'max mark', how about 210? I ask only because I have seen it get up that high a couple times.

 

The thing I'm REALLY worried about... is that it REALLY seems to react a lot ot ambient temperature changes, and I haven't driven it on a really hot day (california hot, 90*+) since I started noticing this problem... I keep thinking the day I finally take it out and it's really hot out that 210* is only gonna be the beginning of my problems......