My 1990 TJ is over heating. I have replaced the radiator, put a 165 degree thermostat in, replaced the clutch fan and I have replaced the water pump. The truck stays cool when idleing, however when driven it over heats within minutes. I am starting to think that it could be a head gasket, but there is not coolant in the oil or anyother signs. I have tried burping the system a few times and I still have no results. Can anyone think of anything else that I may try before i do a head gasket?

 

Dude u have replaced everything, except the head gasket...try to tighten the head bolts a bit.

 

How can I check if I have a torn gasket without taking eveything apart?

 

Check piston compression.

 

How critical are those vacuum connections? some were loose or disconnected. Know where i can get the part numbers for those pieces in there? I've searched for a list but have come up with anything yet.

Would a clogged radiator prevent the temp sensor to turn on the aux fan?
Need to test the temp sensor next. water pump doesn't leak, everything on the engine side is straight. on the 90, does the radiator slip out or is it welded in? i'm going to pull the front end, check the fan clutch, temp sensor, flush rad.

Off topic question, steering wheel is loose, would changing the front stabilizer help?

 

The radiator just slips out. Undo the top cross piece and it will lift out. A clogged radiator will not affect the fan switch.

 

The only important vacuum lines are the ones that go to the map sensor and the fuel pressure regulator, all other can be closed (never live one open)
. I'll have a look at the parts catalog for the codes and post later.
A clogged radiator will reduce the water flow and cool not enough. The the fan should turn on the same.
The radiator is not bolted to the frame, u need to remove the upper metal cover under the hood.
For loose steering wheel what do you mean? If you mean that it turns too easily, it might be the damper.
If u mean that it has some play, u should check the steering linkage for worn ends.

 

I've been searching for a diagram or list for the vacuum lines, I need to make sure all the lines are connect correctly. I've been driving the jeep this whole week and it hasn't stepped above 210 so the cooling is much better. I just need the aux fan to work properly. So if its not the rad or the temp sensor, it must be the relay switch, right?

The steering wheel turns like butter which i love, however its hard as hell to keep it straight or whatnot when driving on the hwy. I'm constantly correcting, i would have to say it feels like there is play.

 

Hope this helps.

 

Wow! That's exactly what I've been trying to find for the past few days! Slick setup. Just need to know a couple things:

- Any clearance issues between the passenger side fan and the pulley the stock clutched-fan was on?

- How did you wire the passenger side fan? I figure the driver's side fan just gets wired into the same connector used for the stock aux fan, but can you detail where/how you wired the other one? Relays used? Wires you tapped into?

- Are the fans on yours equal in size or one big, one small? The only ones I can find on eBay have a bigger fan on the left (driver's side) and a small one on the right.

- Any idea what CFM the Audi fans pull? I'm in Phoenix, AZ and need to be able to pull every bit of air through the fins I can get!

I have a new 3-row, all metal radiator on its way to me from Radiatorbarn (previous GDI 3-row just had one of the plastic end tanks blow...no more plastic for me!) and figure this would be the optimum time to upgrade the fans. Also, how pricey was that Audi unit at a junk yard?

Glad I ventured back over to this forum! Thanks in advance for any helpful advice you can offer.

Pyro

 

Thank you.
-I have one finger of clearance between the pulley and the passenger fan motor, this because i have chosen to mount them all to the left in case i want to add two baby 5in diam. fans in the remaining space on the passenger side. I have actually noticed that the pulley edge touches sometimes (very rarely) the fan motor when i accelerate hard in reverse. This can be easily avoided by mounting the fans more to the left.
-The wiring was something special. At the beginning i wired both fans together on the stock fan relay. What happened is that the relay connectors kept overheating and melting the wires. What i've done is doubling the relays and wires (redundancy) to divide the current in half. At this point i had two choises: run the fans separately each with one relay or run the fans together using both relays (40amp) in parallel. I have chosen this option because if one relay breakes the other will still run both fans instead of only one. Then i have screwed another thermo switch under the tranny fluid lines, on the passenger side of the radiator that switches at 155 °F, i could run one fan at 155 and the other at 192 if i would, but i prefer they come on together.
- The fans are equal size although one is mounted more in and the other protrudes a little more.
- I don't know the CFM value but i know that when the fans come on u can watch the gauge sinking from 210 to 170 in less than 10 seconds, the heat that comes out from under the jeep is impressive, i remember stopping at a lamp and a mother with his child were crossing behind me when the fans suddenly came on i saw the child starting to cry scared from the heat.
The fans costed me nothing because i had this entire audi for pieces and reused several parts in different cars and jeeps.
I know that Mercedes fans will work as well, BMW has a single big one that might be experimented.
I am very satisfied with the audi fans.
I know there are some older audi fans that have one big motor and the two fans are connected with a small belt.
I have had those aftermarket fans they sell at autoparts and they are crap. Slow, and the blades are badly shaped.

 

Ah i forgot to say that i have a switch to run them continuously if i want with a led that tells me whenever the fans are on.

 

Hey everyone, just jumping in here.

I have a very similar problem on my 98 xj. It's got the 4.0 w/ auto tranny.

A couple things, I blew a freeze plug (had a block heater, the retainers on that rusted and gave) and honestly didn't know untill it died at a stoplight and steam poured out. If I had to guess, I would say it ran up to three or four minutes in city traffic with a completely blown freeze plug, I didn't know because I was moving the whole time and therefore didn't see the steam, in hindsight I knew kinda when it blew because it started idling kind low/rough, but I foolishly thought nothing of it. Temp gauge didn't move this whole time...
So, I pulled over, turned off, let it sit and put a gallon of antifreeze in it and limped it the other five minutes home.
I've since discovered it was the freeze plug, bought one of those expandable rubber ones (I think it was 2 1/4") slapped it in, filled it up with antifreeze, and started it up, to my surprise it started, so it wasn't seized. But After driving till warm, Idle was still a little iffy (about 500ish when in drive and idling with the brakes on), so I drive home, turn it off, and go inside to ponder the situation. Come back out a minute later, turn the ignition on, and the temp gauge redlines.

This one thread has been a good source of info and I'm confident I can weed out the issue just on this one thread, but my question is, is it safe at all to drive in it's current condition. Specifically, I'm worried about the temporary freeze plug and since it's so large, I'm worried about it possible restricting coolant flow, is this something to be concerned about it, or can I drive it to a garage so I can work on it for real?

I've still gotta burp it and make sure it's got all the coolant it needs, I'm sure I'll be able to find a write up on that...

I live in apartments so I'd have to drive it to my parents house to wrench on it (about 40 minutes away, in hot hot Arizona Summer weather), just wanna know if this is feasible. I live a 5 minute walk from a CSK, so I'm set on that front.

Also, got an offer from a good mechanic friend to replace all the freeze plugs and "steam clean" the engine for 250 bucks, should I hit it up? Or should I just flush the whole system myself?

Thanks for the help!

Nason.

 

You should be OK with the expandable freeze plug. Folks have been using them a long time. It won't appreciably affect coolant flow. However the rough idle might be something to be concerned about. My guess, and I would be surprised if it wasn't, is that you also blew a head gasket. The thing about blown head gaskets is that you can drive weeks or minutes with them. So when you drive to your folks house, take along plenty of water just in case it starts spitting it out the overflow.

 

Good point, hadn't thought of that. It's kinda oily around it anyways, I'll just replace it...
Do "they" make felpro head gaskets for these engines?

Also, the deal my mechanic buddy offered me, yes or no?