10-16-2005, 11:18 PM
Hi guys,
I've been searching around for some insight into a recent overheating issue, and I'm still confused. If anyone has some suggestions, I'd apreciate the help!
'92 cab
105,000 mi
Rebuilt (not new) waterpump replaced along with thermostat and belts at about 98,000, and it's been running fine temp wise before and since. No recent engine work, so I haven't recently changed anything...
All of the sudden it ran up to the top of the temp gauge. I blasted the heat and it stabilized at the upper end long enough to get me home without lighting the warning light.
Both fans were running, and no visible coolant leaks. Coolant was a little low, so the next day I topped it off and bled it till solid fluid came out the top. I took a trip around the block and it was heading straight back up!
I got back without ventuing into the red light again and checked again under the hood. There was coolant passing through the small overflow line into the expansion tank, the one near the cap. I don't know if that's normal, but it looked to be circulating, so I took that as a positive sign for the waterpump. I've read that sometimes the rebuilt ones go bad.
So I started to tinker. I pulled the radiator and it did have some rust scales in the upper hose side. A magnet pulled out a little over a coke bottle cap's worth, although a couple of pieces were relatively large.
There was a slight discoloring on the bottom of the upper hose side against the fans (i'll try to get a pic if anyone wants to see) that I took for either possible evidence of something different happening in that area, or something spilled there... It almost looks like that whiteish corrosion you see on aluminum, but it's very faint. The rest is clean along with the a/c unit in front.
I ran some hot water through it and there weren't any serious temperature differentials along the face. It seemed to be a little slower to react along the bottom(stained area), but nothing dramatic. Probably my imagination.
Then I started to worry about the head gasket. Compression test reads 195, 190, 180, 185. I haven't been able to find any specific reference for what I should be reading in the shop manuals or online, but 10% variance doesn't seem too terrible, or at least not obvious for a quick non-repeated test.
I'm going to see if I can borrow a leak-down tester tomorrow and maybe locate someone in town that will test the plastic radiator. I guess I should just replace the thermostat while I'm in there. Maybe I should have done that first? It just seems like I replaced it yesterday, but I guess it's been about a year and 7k miles.
Is this pointing to anything obvious??? Thanks in advance.
-RB
btw- I really always loved 968.net. There were so many times that my problems were solved there along with just as many times that I found inspiration for new projects. That said, this is my first post to 968forums and I have to say that the interface and functionality are in a different league. I'm not familiar with the politics, but big thanks to everyone involved in both sites for keeping us in the know. <img src="/forum/images/smilies/968/biggrin.gif" class="smilie" alt="" />
I've been searching around for some insight into a recent overheating issue, and I'm still confused. If anyone has some suggestions, I'd apreciate the help!
'92 cab
105,000 mi
Rebuilt (not new) waterpump replaced along with thermostat and belts at about 98,000, and it's been running fine temp wise before and since. No recent engine work, so I haven't recently changed anything...
All of the sudden it ran up to the top of the temp gauge. I blasted the heat and it stabilized at the upper end long enough to get me home without lighting the warning light.
Both fans were running, and no visible coolant leaks. Coolant was a little low, so the next day I topped it off and bled it till solid fluid came out the top. I took a trip around the block and it was heading straight back up!
I got back without ventuing into the red light again and checked again under the hood. There was coolant passing through the small overflow line into the expansion tank, the one near the cap. I don't know if that's normal, but it looked to be circulating, so I took that as a positive sign for the waterpump. I've read that sometimes the rebuilt ones go bad.
So I started to tinker. I pulled the radiator and it did have some rust scales in the upper hose side. A magnet pulled out a little over a coke bottle cap's worth, although a couple of pieces were relatively large.
There was a slight discoloring on the bottom of the upper hose side against the fans (i'll try to get a pic if anyone wants to see) that I took for either possible evidence of something different happening in that area, or something spilled there... It almost looks like that whiteish corrosion you see on aluminum, but it's very faint. The rest is clean along with the a/c unit in front.
I ran some hot water through it and there weren't any serious temperature differentials along the face. It seemed to be a little slower to react along the bottom(stained area), but nothing dramatic. Probably my imagination.
Then I started to worry about the head gasket. Compression test reads 195, 190, 180, 185. I haven't been able to find any specific reference for what I should be reading in the shop manuals or online, but 10% variance doesn't seem too terrible, or at least not obvious for a quick non-repeated test.
I'm going to see if I can borrow a leak-down tester tomorrow and maybe locate someone in town that will test the plastic radiator. I guess I should just replace the thermostat while I'm in there. Maybe I should have done that first? It just seems like I replaced it yesterday, but I guess it's been about a year and 7k miles.
Is this pointing to anything obvious??? Thanks in advance.
-RB
btw- I really always loved 968.net. There were so many times that my problems were solved there along with just as many times that I found inspiration for new projects. That said, this is my first post to 968forums and I have to say that the interface and functionality are in a different league. I'm not familiar with the politics, but big thanks to everyone involved in both sites for keeping us in the know. <img src="/forum/images/smilies/968/biggrin.gif" class="smilie" alt="" />
