alexgsim

First of all, let me apologize for the length of this post. Now we move on.

I've only had her for a few months now but I really love this car. My 1985.5 944 base is running hot out of nowhere (sort of) and the problem seems to not be easily solvable after 3 and a half weeks. My mechanic and I are almost there, but I just want some more feedback because the work we're doing is exploratory and God knows whether this is gonna work.

Let me take you through the full story:

When I bought the car in mid-May, just over 3 months ago, everything was running fine, except the engine was running hot at idle and city traffic (I live in NYC). getting to the 3/4 line and flirting with the red. When I revved the engine, it would go down a bit. I saw someone on another site had similar symptoms and found it was a non-OEM thermostat that caused his increased engine heat. Lo and behold, the thermostat in the car was a non-OEM one. I replaced it, the temperature stayed right smack in the middle of the gauge. Perfect. Right up until 3 weeks ago.

Immediately after this I had the timing belt changed because I had no idea when it was last changed. Perfect. The shop that did the work here in Queens also found an oil leak somewhere around that area and sent a photo. It looked as if one of the PO's just jammed something in there and messed up the gasket doing it. Probably the previous previous owner since the last PO was a (diesel) mechanic and told me he didn't get to the water pump or timing belt during the year he had it. Anyway, great.

Then about one and a half to 2 months ago I took a trip out to Riverhead, about 75 miles away, and some of the roads leading out of the city are just horrendous. After subjecting my car and girlfriend to maybe 2 miles of complete [colorful words] roads, it must have shaken something loose. On the way back from Riverhead, there was a terrible ratting coming from somewhere. I found it was coming from the exhaust pipe, and then the very next day a few miles from home I had a severe acceleration issue, and it felt like I lost half my cylinders. My poor car sounded so weak and feeble, and I couldn't get it beyond 40 mph. After a day of panicking, I correctly diagnosed that the catalytic converter was completely clogged and totally shot, and when I had the same shop weld a new one in, it was running better than ever. Very happy. Both the car and myself. No rattling, great noise, and great performance.

And then almost 4 weeks ago I went to visit my parents in Massachusetts. it's a 200 mile trip, and the car did great. When I got there, I surprised my parents with my car (I hadn't told them that I'd bought it yet) and my excited father wanted to take it for a test drive. So we went, and had a fun ride around the neighborhood, but he said the temperature gauge was doing crazy stuff. Oh dear.

I thought maybe it was the windshield wiper fluid my dad put in to top off my coolant. He said it really didn't matter, and even if it did, there was no way it'd cause the needle to jump all the way up to above the 3/4 line. I decided to drain and refill it with the proper phosphate-free 50/50 coolant/water, but the problem was no better. We checked the engine oil. [Sigh] the engine oil. I parked on the driveway which is at an incline, maybe 25-30 degrees, and checked the oil 10 minutes after shutting off the engine. The dipstick only had a tiny bit of oil at the very end of the stick. What the holy flying...

I was completely horrified. I don't know if the incline affected the reading or not, but I think the fact of the matter was I had run the car 200 miles on dangerously low engine oil. We also found that there was an engine oil leak which was dripping off the oil pan, so I probably lost a bit on the way. I couldn't believe I hadn't checked something so obviously important and easy to do all the way up until that point. After beating myself up about it and swearing to check the engine oil every time before I start the car (as in the "good" old days), we took my mother's Accord to O'Reilly's, bought SAE 5W-30, and stuck that in my car. Great. But it was still doing that crazy thing with the temperature.

We agreed that it was too dangerous to drive back down to New York, so I told my story so far to a trustworthy shop near my parents' place, and they accepted the job. I originally thought that due to the oil on the driveway that wasn't there before and the heat that it may have been the head gasket, so I mentioned that as well. I took a bus back to NY later that day. Quite sad. I even forgot to bring the burgundy sirloin tips I promised to bring to my girlfriend. Even worse.

The shop called me and they said that the engine head looked good and the head gasket looked fine, so they suspected the water pump was broken and I gave them the go ahead. They called me again a day later, and they said it looked like the water pump was almost new. Hmm. I was one the phone with about 3 of the guys who were standing around my car discussing the best course of action, and we decided that it would be best to check the water pump just in case, and at the same time look elsewhere. While they had the front off, they changed the thermostat (with an OEM one, I might add) because the shop owner wanted to be extra sure that the heating issue didn't mess up the thermostat and also that it wasn't somehow sticking so soon. Since the thing costs next to nothing it was totally fine; I probably would have changed it myself again after getting the car back anyway to be sure of the same.

After confirming the water pump was fine, they decided to change the radiator. It was actually pretty bad; even from the outside it looked so old with tons of junk on it through the front spoiler. I'm sure it looked much worse on the inside. Anyway, good. New radiator. I gave the go ahead for one of the mechanics to take it home to see how it did on the highway, but when he got back in the morning, he reported that it still wasn't completely there yet. Didn't solve it. Not so good.

Next thing was to look at the fans. Seems one of the PO's, I think either the previous previous or previous previous previous owner, had hacked the wiring and installed a physical switch to bypass the cooling fan temperature switch so they could turn it on the low speed whenever they wanted. Except it wasn't actually working properly. The low speed went on, but the high speed never did. So the guys fixed that, took out that stupid physical switch, and put in a new temperature switch. Boom. Didn't work. I actually went back up to MA because we all thought it'd be totally fixed by this, but upon arrival that morning, the owner somewhat sheepishly explained that it still wasn't quite right. The fans still don't spin at high speed. The fans themselves are fine--when they did a bypass and fed power from the battery to the fan, they got it to spin at high speed, but the car wasn't doing it by itself normally. He asked if I would be willing to test drive the car since they were so busy, and I said yes. It was sort of half-fixed: the temperature needle was in the middle with extremely minor fluctuations (barely moving) under 40 mph, but at higher speeds all the way up to 85 mph it was somewhat going up and down right up to the 3/4 line--not going over, but the tip of the needle was just touching it. I also shut the car off for a few minutes, and turned it on again before heading back to the garage. When I turned it on, I missed the first 3 or 4 seconds, but I saw the temperature gauge coming down from above the 3/4 line. I didn't notice or confirm, but the fan probably wasn't on when the car was shut off. And as we know, the fan should be working even if the keys are out of the ignition... Anyway, I want the car to run for at least the next 10 years, and the owner wanted to keep working on it as well since it's such an interesting (and frustrating) case, so I came back home to NY and left the car in the shop. At least this time I remembered the sirloin tips.

Now they're about to try a new fan relay, which should come in early next week, so I should hear more then.

So far, the good news is that the car is getting there. Bad news is that it seems to be a culmination of several issues. (My wallet!) Other good news is that both shops I got to here in New York and up near Boston are really, truly great. They take pride in their work and are very honest. They don't do unnecessary work, and they're not the kind of guys to tell you that you need new brakes or anything if the parts are only halfway there. In fact, they'll tell you that you do have a tiny bit of life in the pads but that you would need to get them replaced in the next 3 months. And I think we all know how hard it is to find trustworthy shops...

Now, judging from the work done so far and the current state of the temperature, it does seem for now that the new relay may fix the fan speed issue. However, I would still like to hear some of your opinions and other possibilities in case this doesn't completely work out. I know it's not necessarily the best use of time to think about alternatives when the chosen solution still has yet to be carried out, but I still wanted to at least have one or two likely options if, God forbid, the relay doesn't solve it.

There are several things I ruled out after speaking with the owner yesterday:
-We did rule out the thermostat since I confirmed he put in a new OEM one from Wahler.
-Trapped air in either the engine or coolant system seems to me a beautifully elegant answer, but extremely unlikely. I don't know how trapped air would cause the temperature sensor to behave, but this is a reputable shop we're talking about--I don't think they'd mess up filling up a car with coolant.
-The cooling fan temperature switch was replaced so that should be working fine...

Does anyone have any ideas? It can't be the air filter can it? I would think I'd notice a reduction in power before increased engine heat... But I don't have the experience to say.

Again, apologies for the novel, and any help would be greatly appreciated.

marc abrams

Hum, sounds like the gauge is wigging out. Mine was running hot also, or at least indicating that. I did a write up a few months ago about this. Although I have a early Car the principles are the same. I reflowed the solder joints and it's been a reading a soild 87c/188f ever since. And that's in 90+ degrees weather.

​​​​​https://rennlist.com/forums/924-931-...-write-up.html

alexgsim

Thanks a lot for the suggestion, this could also explain why the high speed fans don't come on--if the temperature reading is high but the ACTUAL coolant temperature is lower than the high speed threshold, it would explain everything as of now.

Next week once the relay comes in we'll see if that solves the fan issue, but if the needle still acts abnormally, the guys will take off the instrument cluster and take a look there (and replace the bulbs since my gauges don't light up when I have my headlights on... ).

Mr. Toasty

Reading through this thread, I think marc abrams is right about the gauge. Keep us posted!

Before you replace bulbs, check the fuse for the dash lights. It's probably blown. That's a very common failure, and chasing down a complete fix can be difficult. Also, while you're in there, check the condition of the three large reflectors on the bottom of the gauge cluster. They're probably faded and not very effective, but refurbishment is not a difficult job.

mro763

Use a laser temperature gun to see the temperature of the engine. when it reaches normal operating temp. Then when the temp gauge goes up re-check the temp using a laser temp gun to see if the temp went up. If it didn't go up then its probably your gauge. You can get a temp gauge for cheap at Harbor freights or any auto shop place.
Good luck!