Overheating Update

Well, the overheating and coolant loss are not being caused by a blown HG/cracked head/cracked block.

Did a comp test and leak down test, and all were good. No oil in the coolant and no coolant in the oil.

The coolant loss is coming from the lower radiator hose...ever so slightly.

The temp gauge is also inaccurate. At 210 it is on, but past that is is grossly off. When I think I am overheating, the engine temp is only about 225. New coolant sensor for the back of the block.

Now, for the weird part. The mech showed me some gunk that he could scrape out of the filler neck. He asked if I had put any stop leak in it as that is what it looked like.

I am taking the rad to a shop to have it "rotted"(I think that is the term). I will do a complete system flush before hand, and make sure it is nice and clean before the rad is put back in.

I havent figured out the electrical problem yet, so I still don't have dome lights or a CD player.

Fergie

A compression/leak down test will not always show a small leak in the head gasket.Gunk in the filler neck is definately on the list as an indicator for a combustion leak.

The only way to really confirm a leaky head gasket tends to be a sniffer in the radiator. They also make a liquid and a mechanism that sniffs the gas from the radiator and bubbles it though the fluid. The fluid changes color if there are combustion byproducts, signifying a head gasket leak.

if you have a blown head gasket you would be able to tell from you exhaust it would be very white

RCP Phx said:

A compression/leak down test will not always show a small leak in the head gasket.Gunk in the filler neck is definately on the list as an indicator for a combustion leak.

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Both you and Tom SUCK!

I don't wanna hear that dammit!

I have been told from different folks that sniffer test can be just as inconclusive as leak downs and comp tests.

What do y'all think?

Fergie

Fergie said:

Both you and Tom SUCK!

I don't wanna hear that dammit!

I have been told from different folks that sniffer test can be just as inconclusive as leak downs and comp tests.

What do y'all think?

Fergie

Click to expand...

I here ya!Just went thru this on a Toyota 22R.Never seen a motor go from stone cold to flaming hot in 5 minutes!Combustion pressures/temps are usually to hard to simulate with air.

well, we'll see if the rad rotting helps the problem any, and I'll replace the hose while I am at it, then I'll see.

Fergie

I think the word you want is "rodding" - they take the tanks off the radiator and run metal rods thru the tubes to push the crap out, after it's been boiled.

If the mech was able to scrap a bunch of crap out of the gooseneck, then the buildup in the system is probably something I'd sooner not think about. It takes 1/14" of buildup of any sort of crud to cause a 10% loss of efficiency - you've probably got problems.

The gage being off is probably partly due to buildup in the system (possible) and the sensor "losing its curve" (also possible) - which means that it's still accurate near the centre of the span, but the ends are no longer changing resistance proportionate to the temperature changes. You might want to make sure the other temperature sensor(s) (what year is this thing?) are still in working order - whenever I've seen one go to Hell, usually they all go at once.

It is possible that a leakdown might miss a very minor leak due to the low temperature air of the leakdown, but let's concentrate on the stuff we can see before we start playing "what-if?"

5-90

So what would you suggest as a fool proof test?

I need to know as this thing is my daily driver, and don't have an extra vehicle anymore.

Fergie

I hate to tell you this, but there is no such. The closest you can get is a teardown and inspection - and that still suffers from the problem of deciding whether the gap in the gasket was caused during service or when you pulled it out.

Do a serious flush of the cooling system this week-end, if you still have the XJ in service. If that doesn't do it, then either get the radiator rodded out or replace it - and if you replace it, it might not be a bad idea to have the old one boiled and checked for service as a spare (for your next XJ of course - I don't expect you to stay down to just one for long...)

There's a good reason that a two-year flush interval is recommended often - it works. Even if it's just a "hot-water" flush, drain, and refill, you need to break up the crud that will start collecting and get it cleared out, then new coolant (as you probably already know, that stuff doesn't last forever.)

5-90

Well, after buying my super dooper CSF 3 row, it turns out that I have a broken tube, after just 10 months of use.

No offroading, not weird driving, just normal everyday use.

CSF will no longer my vote of confidence.

2-row Modine from Napa here I come!!

Fergie

One of the reasons I'm so partial to that 7 hour prestone flush that I mention all the time is it dissolves build up not only in the radiator but in the whole cooling system and does not try to blast it out like the shorty flushes do. EVERY TIME I've tried a 15 min flush I've ended up replacing a water pump within a month because it does something to the seals.
Unfortunately the layout of the XJ rad tanks does not let you look at the end of the tubes. In my S10 I could see the results of the stuff and how much it cleaned the rad out, enough that I was a bit nervous once the solder got real real shiny as in brand new looking. I was afraid it would eat the solder but it didn't.
Did any of you happen to read this info , I thought it was interesting that the protectants in the anti-freeze immeadiately bond with the radiator to protect it from corrosion as soon as you pour it in and how fast it can corrode depending on the water you use like in waco tx....

Geez - and you all wonder why I keep suggesting Modine!

I find a brand I like, I'll stick with it until I have reason to do otherwise. I have yet to get reason to do otherwise from Modine - the (VERY!) few times I've gotten a bad part from them, it got made right - and quick!

5-90