Hello,

I changed the oil thermostat myself, but the o-ring seal was not correctly placed and coolant was leaking, but don't know how much was spill when the engine was idling to warm up and test it. When I took the thermostat out, I realised the o-ring was broken.

I have tried to place the o-ring from the old thermostat, but it is simply impossible to fit it correctly, when you think it is inside, there is always part of it out. I will buy another one o-ring and try.

But I am worried because the engine was idling for a while (5-10 minutes) to test the new thermostat, there was coolant in the expansion tank. And when I got into the car to accelerate the engine for 1 or 2 minutes, I noticed engine vibrations while decelerating from 3000 to 1500 rpm, so I went out to take a look and the expansion tank was empty. Temperature gauge inside the car was about the half mark of regular idling temperature. I immediately stopped the engine. I think that this point coolant was leaking (the oil thermostat itself) is a critical point, because it is at the botton of the engine and is the inlet path to the engine.
My bad head tends to think that it is possible that the engine block didn't have enough coolant inside when I got into the car and began accelerating, and something got damaged, and then I noticed the vibrations. And the temperature gauge was not indicating overheating because there was no coolant passing through the coolant temperature sensor. (Could the engine have overheated in spite of the low temperature indicated by the gauge?)

Is it possible that the engine or something was damaged in so short? Why those vibrations? Please give reasons for your answer. I am really really worried about it.

Thanks.

 

ernest0, if you were only idling the car other than the 1-2 minutes for the slightly higher RPMs, then all should be good. As for the rough engine, with having a diesel engine, this is something that I can't speak to as it works on a slightly different principle and I know just enough to be really dangerous. I would hate to send you on a wild goose chase. But, something is telling me that the computer was altering the fueling times, leading to the rough idle.

I would say to redo the o-ring (may find applying just a little bit of RTV or a gasket maker to the o-ring to hold it in place will prevent it from sliding around on you again) and then fill up the system and see what you have then.

From my experience, when an engine looses all its coolant, the temp gauge will actually drop as it is not getting a true temperature reading and actually starts to get cooled by the "cold" air under the hood (relative to the temperature of the engine). since you had a normal reading, things are probably just fine.

 

Thanks Thermo. This is good news for me!

I didn't know anything about the existence of RTV. I have taken a look at it right now. Where do you think I should apply the RTV? Over the new o-ring or just create a new seal only using RTV? I have attached a photo of the actual thermostat for clarification (jag part #jd61162).

 

you may be able to get a replacement o ring from your auto local parts store.
Take your old ring with you to compare.
If not you should be able to fine one at your local plumbing supply store or even the hardware store.

worst case try.

 

Thanks Paul, but I am right now going to pick up a new o-ring to the nearest Ford's, I gave them a call and they have it.

 

Yeah, I wouldn't try to seal it with RTV...it would only be a temporary fix at best..

My concern here due to lack of information...Is, where did the coolant go? was it leaking out of the engine onto the ground, or INTO the engine and now has settled into the sump with the oil..which in that case, overfilled the sump and would cause the pistons to slap the overfilled sump mixed with coolant and oil..causing the engine vibrations..I know diddly squat about the diesels in these cars, but this is what came to my mind.

 

+1 to Thermo's encouragement that the engine is probably ok. You had coolant in the engine while it ran for ~5-10 minutes. Yes, some leaked out, and some was still leaking after you shut off the engine. The coolant thermostat was not bathed in liquid, but it was bathed in steam rising up from the liquid coolant, and the temperature gauge still did not spike, so you're engine's probably ok.

If any damage occurred, it would likely be the head gasket. If you're still concerned, check the compression and check the oil for coolant to put your mind at ease, then grab a beer for "medicinal purposes".

 

The coolant went onto the ground.

 

Yep, I hope everything is ok.

 

Well, thermostat is in its place now with new o-ring seal. I don't know why, but this one was super easy to fit using vaseline while the other one wasn't, maybe bad o-ring...
Yesterday the thermostat was out till all the coolant possible went onto the ground by that path.
Now I was doing what JTIS tells me to do to refill the cooling system.
Loosen the air bleed screw.
Fill the tank
Tighten the air bleed screw.
Start the engine, 1500 rpm for 20 sec.
Switch the engine off and fill the tank to the max.
Start the engine, idle for 2 minutes and then 3000rpm until the fan operates, observing the engine temperature gauge.
At this point, after 2 minutes idling and 2 more at 2500-3000rpm, the temperature gauge was still indicating the minimum. So I switched the engine off. ŋ?
Is it possible that no coolant is passing through the sensor? Remember I had the thermostat out of its place until no more coolant was falling. If this is the case, then when will the fan operates if the gauge is not sensing the increase?
Maybe what I am thinking is totally wrong, and I should only keep the engine at 3000 rpm for a long time. Does anybody knows if I will be on the safe side doing this?

 

Fixed! I finally end waiting with A/C on and at 2500 rpm. I couldn't get the fans to operate, but temperature was rock stable between 80-90 ēC, which is nearly touching the vertical certered line of the gauge range. I think it's been more than 2 years suffering the low temperature problem! :-)

The old o-ring seal was definitely impossible to re-fit due to wear, the internal circunference was not touching all the thermostat as is the new one, so you know: don't try to fit the old one if it doesn't enter in the first 5 minutes, and don't lose your time as I did breaking my back for 1 or 2 hours, driving me nuts.

As far as I can tell right now, engine seems to be OK.

Thanks to everyone.


FIXED