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Overheated, now it runs very rough
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bureau13  



Joined: 07 Sep 2017
Posts: 202
Location: South Florida

PostPosted: Sun Mar 10, 2019 9:01 am    Post subject: Overheated, now it runs very rough Reply with quote

So for a while now I've had the symptom of a cooling fan problem (gets hot in stop and go traffic but not on the highway) despite my fans appearing to operate properly. I've had the temp gauge needle get pretty close to the red area but never actually overheated, until today. I went to a car show, and there was no parking, and suddenly I had steam coming out from under the hood. When I raised the hood, lots of liquid was dripping off the underside of it.

Anyway, I got some distilled water and filled it up, started it, it seemed to run OK and didn't appear to be leaking, but when I started to drive home I got maybe a quarter mile and then it got really rough, rpms at idle would randomly drop to almost nothing, etc. So I had it towed home. What has happened here? It wasn't really apparent where the coolant came from, and I realized I'm not actually sure how this car handles overpressurized coolant. Where does it vent? And why is my car now running like crap. Ugh...worst car show ever!
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-----------------------------------------
1982 931
1986.5 Silver 928S
2007 Hummer H3 (Daily Driver)

Past lives (I miss them all):
2004 RX-8 (Wrecked)
1993 RX-7 (Sold)
1987 RX-7 Turbo II (Sold)
1985 RX-7 GSL (Stolen)
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bureau13  



Joined: 07 Sep 2017
Posts: 202
Location: South Florida

PostPosted: Sun Mar 10, 2019 9:20 am    Post subject: Reply with quote

Update: I was wrong about it not leaking. I just looked at the overflow tank, which I refilled and haven't driven, and it's empty. I filled it again, and coolant is running down my driveway. I can't yet tell where it's coming from, but it does not appear to be from the front of the engine. Which seems odd...water pump area seems dry, radiator, the hoses I can see from the top...I don't see any leaking there. Where are other likely leak points, especially given the overheating experience. And would the coolant leaking out cause it to run poorly if the temps weren't hot?
_________________
-----------------------------------------
1982 931
1986.5 Silver 928S
2007 Hummer H3 (Daily Driver)

Past lives (I miss them all):
2004 RX-8 (Wrecked)
1993 RX-7 (Sold)
1987 RX-7 Turbo II (Sold)
1985 RX-7 GSL (Stolen)
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Kenodog  



Joined: 25 Jun 2003
Posts: 2580
Location: Vancouver,B.C.

PostPosted: Sun Mar 10, 2019 11:08 am    Post subject: Reply with quote

Cracked head....you put cold water in a hot motor. The rough running is water getting into the cylinders.





Me
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1979 Euro 931, Olive
1981 931, Sabine
2014 Mazda CX-5 (Kinderwagon)
2008 GS500
2016 DR650
2019 KTM 790 Adventure
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Fasteddie313  



Joined: 29 Sep 2013
Posts: 1853
Location: MI

PostPosted: Sun Mar 10, 2019 12:20 pm    Post subject: Reply with quote

Yep..
Hopefully just a head gasket but it has to be something like that to cause it to run poorly..

Or, if you are super lucky, maybe it blew one of those hoses off the back of the head, like a heater core hose back there, and the water is just messing up your ignition..
Like got water in your distributor or something..

As far as where the leak is coming from check the hoses coming out of the backside of the head and follow them.
Their is also one under the intake manifold I think you can get to be removing the alternator..

The cap on the expansion tank is supposed to be the blowoff point.
I think the cap is supposed to let go at 15-20psi or something like that..
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Kenodog  



Joined: 25 Jun 2003
Posts: 2580
Location: Vancouver,B.C.

PostPosted: Sun Mar 10, 2019 2:59 pm    Post subject: Reply with quote

Head gasket is excessive cylinder pressure, not heat. A glowing hot head and cold water spells dissaster. $10 says it's cracked.

Sorry bro, hate to put it like that.




Me
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1979 Euro 931, Olive
1981 931, Sabine
2014 Mazda CX-5 (Kinderwagon)
2008 GS500
2016 DR650
2019 KTM 790 Adventure
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Paul  



Joined: 02 Nov 2002
Posts: 9413
Location: Southeast Wisconsin

PostPosted: Mon Mar 11, 2019 2:30 am    Post subject: Reply with quote

Pull the plugs, do a compression test.
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White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
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bureau13  



Joined: 07 Sep 2017
Posts: 202
Location: South Florida

PostPosted: Mon Mar 11, 2019 2:52 am    Post subject: Reply with quote

Hmmm...well I didn't put the water in right away. It was a good hour or two later. So hopefully that's not it.

Also, I did find the (or at least a) leak...the short hose at the back of the block that's on top...I'll need to remove the distributor to get to it I think.
_________________
-----------------------------------------
1982 931
1986.5 Silver 928S
2007 Hummer H3 (Daily Driver)

Past lives (I miss them all):
2004 RX-8 (Wrecked)
1993 RX-7 (Sold)
1987 RX-7 Turbo II (Sold)
1985 RX-7 GSL (Stolen)
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bureau13  



Joined: 07 Sep 2017
Posts: 202
Location: South Florida

PostPosted: Mon Mar 11, 2019 4:41 am    Post subject: Reply with quote

I managed to get the hose out. One end is connected to what appears to be a small thermo-switch. No idea what it's switching, but one of the vacuum connections has nothing attached to it, so whatever it was was never working.

FWIW, the insides of the distributor did not appear wet. Still, I'm holding out hope that it was related to something like that. The engine really did not seem particularly hot when I added the water. I guess time will tell. I've ordered the hose (hopefully it's the right one, it shredded while pulling it out and I can't read any part numbers on it) so I'll post what happens when I get the new one on and try it out.
_________________
-----------------------------------------
1982 931
1986.5 Silver 928S
2007 Hummer H3 (Daily Driver)

Past lives (I miss them all):
2004 RX-8 (Wrecked)
1993 RX-7 (Sold)
1987 RX-7 Turbo II (Sold)
1985 RX-7 GSL (Stolen)
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Fasteddie313  



Joined: 29 Sep 2013
Posts: 1853
Location: MI

PostPosted: Mon Mar 11, 2019 6:22 am    Post subject: Reply with quote

bureau13 wrote:
I managed to get the hose out. One end is connected to what appears to be a small thermo-switch. No idea what it's switching, but one of the vacuum connections has nothing attached to it, so whatever it was was never working.


Pics or video of these?

It sounds like your thermotime switch in that water hose housing thing bolted to the back of the head. It makes your cold start valve operate..

The vac hose in that area sounds like your distributor vacuum lines..
You need your distributor vac advance and boost retard to work correctly or your engine might run badly or blow up in boost..

All of your vacuum needs to be right..
You can trace all of those small lines either from the nipple on your TB or down there by where your brake booster gets it's vac..
If they are still those cloth braided small lines they need to be completely replaced. Mine looked fine on the outside but inside the rubber was just crystallized..
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bureau13  



Joined: 07 Sep 2017
Posts: 202
Location: South Florida

PostPosted: Mon Mar 11, 2019 6:28 am    Post subject: Reply with quote

Things are complicated somewhat on my car by the fact that it's a series 2 with no DITC. Instead, someone has replaced it with a distributor w/ vacuum advance (but no separate vacuum retard) and some strange vacuum routing using what looks like an solenoid between vacuum source and the vacuum advance. I haven't figured out exactly how it's working if indeed it is.

Fasteddie313 wrote:
bureau13 wrote:
I managed to get the hose out. One end is connected to what appears to be a small thermo-switch. No idea what it's switching, but one of the vacuum connections has nothing attached to it, so whatever it was was never working.


Pics or video of these?

It sounds like your thermotime switch in that water hose housing thing bolted to the back of the head. It makes your cold start valve operate..

The vac hose in that area sounds like your distributor vacuum lines..
You need your distributor vac advance and boost retard to work correctly or your engine might run badly or blow up in boost..

All of your vacuum needs to be right..
You can trace all of those small lines either from the nipple on your TB or down there by where your brake booster gets it's vac..
If they are still those cloth braided small lines they need to be completely replaced. Mine looked fine on the outside but inside the rubber was just crystallized..

_________________
-----------------------------------------
1982 931
1986.5 Silver 928S
2007 Hummer H3 (Daily Driver)

Past lives (I miss them all):
2004 RX-8 (Wrecked)
1993 RX-7 (Sold)
1987 RX-7 Turbo II (Sold)
1985 RX-7 GSL (Stolen)
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bureau13  



Joined: 07 Sep 2017
Posts: 202
Location: South Florida

PostPosted: Mon Mar 11, 2019 7:48 am    Post subject: Reply with quote

For reference, here are some pictures, first in situ and actively leaking, and second after butchering it during removal:

https://photos.app.goo.gl/5yQ6RvRVj13AiqZp8[/url]
_________________
-----------------------------------------
1982 931
1986.5 Silver 928S
2007 Hummer H3 (Daily Driver)

Past lives (I miss them all):
2004 RX-8 (Wrecked)
1993 RX-7 (Sold)
1987 RX-7 Turbo II (Sold)
1985 RX-7 GSL (Stolen)
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bureau13  



Joined: 07 Sep 2017
Posts: 202
Location: South Florida

PostPosted: Tue Mar 19, 2019 4:21 am    Post subject: Reply with quote

Update (but not much of one):

I replaced the hose, so it no longer leaks. Filled it up started it. It seems to run "fine"...on about 3 cylinders. No coughing and sputtering, it doesn't want to die although it didn't start super easy, but a lot of vibration and it sounds like an old Beetle. I drove it around the block, and it performs like an old Beetle as well.

I have new plugs and wires, but I've hit a snag there (Not sure how this is related anyway). My car is an '82 but someone has replaced the DITC with a distributor at some point. The Kingsborne wire set I got doesn't fit on the distributor end...I don't know how wires are supposed to attach with the DITC, or if my distributor is even set up like the stock earlier cars. There are metal terminals protruding from the cap that look similar to spark plug ends, and the Magnecor wires that were on there have a clip recessed in the boot that clips on to those ends. The new wires have a metal clip protruding from the boot that looks like it should be inserted down into a hole to clip to the contact. Not sure if these are replaceable connectors on these wires or not, but I'm hesitant to spend more money on ignition bits unless I know that's the problem.

I was going to do a compression test but none of my spark plug sockets fit. Which is weird, because my 13/16 seems to fit the replacement plugs I bought (and it worked on my 928). Anyone have the proper specs for spark plugs for an '82 931? Hopefully the PO didn't use something non-standard here.
_________________
-----------------------------------------
1982 931
1986.5 Silver 928S
2007 Hummer H3 (Daily Driver)

Past lives (I miss them all):
2004 RX-8 (Wrecked)
1993 RX-7 (Sold)
1987 RX-7 Turbo II (Sold)
1985 RX-7 GSL (Stolen)
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View user's profile Send private message
bureau13  



Joined: 07 Sep 2017
Posts: 202
Location: South Florida

PostPosted: Sat Mar 23, 2019 2:59 am    Post subject: Reply with quote

I pulled one of the plugs out (I needed a metric socket for it, which seems weird, but OK) and...it's wet with oil. I don't know if that is related to the overheating issue or if it was something I had already and just didn't know about. I need to check the other ones now, and do that compression check.
_________________
-----------------------------------------
1982 931
1986.5 Silver 928S
2007 Hummer H3 (Daily Driver)

Past lives (I miss them all):
2004 RX-8 (Wrecked)
1993 RX-7 (Sold)
1987 RX-7 Turbo II (Sold)
1985 RX-7 GSL (Stolen)
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Fasteddie313  



Joined: 29 Sep 2013
Posts: 1853
Location: MI

PostPosted: Sat Mar 23, 2019 3:34 am    Post subject: Reply with quote

Could be from a..
Kenodog wrote:
Cracked head....


Clean or replace the spark plug and try running it again..
Any handy br#es b#es bpr#es should work for testing..

Check before, during, and after running for water in the oil, or oil in the water, and a steady stream of bubbles coming onto the expansion tank..
Look for smoke in the exhaust..
What's the oil pressure?
Check the cam oiling under your oil cap..

I like to use the sparkplug tool in the 931 toolkit.. Works good..
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bureau13  



Joined: 07 Sep 2017
Posts: 202
Location: South Florida

PostPosted: Mon Mar 25, 2019 12:58 pm    Post subject: Reply with quote

Well it seems I may not have killed the 931 after all. I changed the plugs..they were all wet, but the remaining three seemed to be gas. Which is making me question my observations of the first one. I'll check it again after I've driven on the new plugs a bit, but the gas could have been me cranking it to get it started a few times, bad wires not allowing a proper spark (and those wires are definitely getting replaced) etc. Who knows...the point is it now seems to be driving the same as it was before this debacle, which is not to say there aren't issues that need fixing, but...I didn't kill it. Yet. Probably....
_________________
-----------------------------------------
1982 931
1986.5 Silver 928S
2007 Hummer H3 (Daily Driver)

Past lives (I miss them all):
2004 RX-8 (Wrecked)
1993 RX-7 (Sold)
1987 RX-7 Turbo II (Sold)
1985 RX-7 GSL (Stolen)
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View user's profile Send private message
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