Gets hot only on highway/ weird oil pressure...

[jared_gibbs]

My apologies in advance for such a long post, I'm just tyring to provide as much relevant detail as I possible. I have done some searching around the forums to see if I can solve this one myself, but it seems that cures for most correctly diagnosed problems on the forums have been simple maintenance, HG problems, or rad problems, most of which I can rule out.

Promlem 1: Engine temp seems okay in town, but temp gradually goes up on the highway. It seems like between 2-2.5K RMP's it'll stay at half way continuously, but after 3k it will slowly escalate. At a constant 70 mph (probably about 3.1 or 3.2k RPM's) in about 20 minutes or so, it will be at about 3/4 and slowly climbing. At this point I can turn on my heater and AC (my logic: heater helps remove hot air and AC kicks on secondary fan), and it will go down between 1/2 and 3/4.

Promlem 2: Weird oil pressure. After I start my engine, it registers as almost nothing. It goes up quickly after just leaving my parking lot to the first mark, and then slowly goes down. It also registers at almost nothing when I idle. It never goes past that first mark. I haven't been able to pick out much of a pattern, is there something I could look for to help with diagnosis?

Problem 3: I've noticed that my valve cover is cracked at one of the bolts. I guess someone over torqued it. Could that be causing these problems? What other problems could it cause?

Possible correlation between these two problems?

Here's a list of all the work I had done on it last week:
Rebuilt head installed, so I can't imagine there's a problem there.
All new gaskets, including head gasket
Water pump
Timing Belt
Oil change, still seems to have same amount of oil
Fuel pump, fuel filter, recharged AC (pretty sure they're unrelated to the issues, but I thought I'd list them anyway)
Engine harness repaired. Instead of getting a new one, my mechanic (and member DSM1G90, thanks again!) agreed it would be easier/less expensive to splice wires from another car. Seems to work, however I wonder if we missed something. My horn doesn't work either...
Radiator work: fans from my junk car (90 gs-t) installed and seem to work. Secondary fan seems to engage sometimes even when climate controls aren't. I do believe there was a crack that was fixed as well. I assume he did a rad flush too, but will call tomorrow to make sure. Not on my invoice, but he was nice enought to give me a few freebies for all the money I put into it.

*Did not replace oil pump.

Should I even be driving this until it's fixed? I've put a ton of money into this car, and I sure don't want to do it again from driving on a hot engine. My friend told me that the oil pressure problems could be signs of a bad bottom end, and to get rid of it ASAP. Any way to rule that out?

I do again apologize for such a long post, and would like to express my sincere grattitude for any suggestions at all. I understand that you guys have put a lot of time/money/energy into your cars, and that my situation is not unique. I've seen you guys help out a lot of newbs like myself, and that is awesome. You guys are the bomb, and I sure hope to see a day that I can offer more to this forum than long posts and questions. Cheers!

 

[97-gst]

What motor do you have? Maybe where youre car is overheating it got your oil hot and its real thin now. First change your oil and you might wanna pick up a thermostat. Either a new valve cover or jb weld it prob wouldnt hurt

 

[gieri002]

I would recommend changing your thermostat and fluid. Does the car smoke at all or "drink" any coolant?

 

[jared_gibbs]

Sorry, I knew I'd forget something on the list of repairs. I did put in a new thermostat and gasket. I got a couple new rad hoses too. The motor is a 1.8L SOHC.

I'm really curious as to what problems the cracked valve cover will cause. I'm a pretty fresh newb, but my train of thought is that if oil can come out of the cracks, couldn't that drop the oil pressure? My friend is telling me no, but I can't help but wonder. Anyway, in this particular case oil is not coming up through the crack. I can feel air coming out of it though when the engine is running.

I don't know if I should start with a new oil pump, guage cluster, sensors, valve cover, etc. It's going to be a small chunk of change almost no matter which direction, I just want to go with the best guess possible.

Could my bottom end really be shot or on its way? Man that would suck. It seems that most agree the 1.8's are strong motors too...

Thanks for the advice 97-gst. Should I grab a heavier weight this time maybe?

gieri002,

I haven't noticed any smoke, would I notice that if it were just idling or would I need to give it some gas?

I've only had it back for a couple of days, so I haven't been able to detect a change in coolant levels. Reservoir was half way when I last checked, I took it for a good cruise to take some notes before posting, so I'll check again to see if it's changed.

Oil seems like it was 3/4 up the dipstick, so I'll check to make sure that's the same.

No noticeable leaks; clear pavement at home and work where it has been pakred. I might throw some cardboard under there just to make sure...

Thanks guys!

 

[luv2rallye]

Have you replaced the rad cap? A leaky one will cause overheat. Also make sure its seat is clean.

 

[BrokenTsi]

I would retorque the head bolts.

A cracked valve cover will only cause oil leaks, nothing else.

If the head bolts arent torqued properly, I can see it overheating and causing oil pressure problems.

 

[jared_gibbs]

Luv2Rallye,

Rad cap looks good and seems to seal well. I sure hope the fix is simple like this!

Broken TSI,

Sorry for my green-ness, but can I mess something up by doing this myself? The most I've ever really done to a car is an oil change. I've read that all I need to do is hand tighten the bolts and then give it a half turn or so and call it good. If it leaks then turn it a little more. Is this method good enough?

gieri002,

Okay, definitely not going through coolant. I noticed the inside of the overflow is lined with black/brown something. Sludge? Normal buildup? I didn't touch it, so I'm unsure of it's consistency or texture. Could it be a mess left behind after fixing the head and HG?

My mechanic wants to put a performance fan in it and call it good. Am I out of line to want the stock parts that originally ran the car to continue to run the car? I feel like this is putting a bandaid on the real issue at hand.

I'm wondering if this all isn't a bunch of small electrical issues. As I mentioned earlier, the original engine harness was mangled pretty badly. My mechanic managed to make it work, but I can't help but wonder if we missed something.

My brother suggested that maybe the fans aren't shutting off on the highway. He is graduating from UTI soon. I guess the fans are supposed to shut off after 40mph because they can't keep up with airflow from that speed?

I'll head out there with a diagram tomorrow and see if I can't figure something out. I bought a new oil pressure sensor too so I'll see what that does.

Thanks again for all your input!

 

[gieri002]

hmmm, well your on the right track. I would defiantly drain and replace your coolant next. Don't have a performance fan put in, I highly doubt that is the problem. (mechanics). The coolant system is quite simple, either you have a leak or it isn't flowing properly and it sounds like yours may not be flowing properly (possibly due to the sludge buildup???) Let us know how it goes.

 

[Bluefire16]

Well if you are getting a brow/black slugg in your coolant sounds like oil and coolant are mixing. This could be from a number of areas, but seeing you just had the head worked on, i would guess your head.

 

[RT-AWD]

Luv2Rallye,


Broken TSI,

Sorry for my green-ness, but can I mess something up by doing this myself? The most I've ever really done to a car is an oil change. I've read that all I need to do is hand tighten the bolts and then give it a half turn or so and call it good. If it leaks then turn it a little more. Is this method good enough?

are you talking about head bolts being hand tightened? if so that is certainly not good enough. you need a torque wrench and tighten the bolts to 72 ft/lbs if stock, if they are arp headstuds its 90-120, 500 miles then re-torque.

 

[jared_gibbs]

RT-AWD,

Many thanks for your advice! Are the two bolts that are immediately visible on the valve cover the head bolts? (SOHC)

Updates:

My license plate was positioned directly in front of the radiator. I removed it and saw a definitely noticeable improvement. It still got hot on the highway, but it took much longer. I'm shocked to see that such a simple thing could cause such a problem. Is it coincidence, or could it really have been blocking flow to the radiator that badly? I'm told by friends that it can't make that big of a difference, but my personal experience indicates otherwise.

I drained all the coolant and threw in some radiator cleaner. As per directions of the cleaner, I am to fill the remaining radiator capacity with water only for the next 3-6 hours of driving. I'm nighing my 3rd hour (intermitent), and not once has the temp moved past half. I took it for a spin through the hills at various speeds, rpm's, and climbs, and it wouldn't budge past half. I have yet to test it on the highway. To completely conclude that the problem is resolved, I'll still need to drain the cleaner and refill with antifreeze. I'm pretty optimistic of the resutls.

I'm pretty sure I was given the wrong oil pressure sensor, it just doesn't seem to fit in there at all. It is right close to the oil filter right? Anwyay, not to worried about that right now. I'll get an oil change after all of this and throw in some 10-30 for the summer.

Thanks again everyone! I'll hopefully post a resolution tomorrow or possibly Monday.