Massive Coolant leak after installing Thermostat

lfoster

Member
Apr 5, 2020
7
0
New Mexico
So I have a 1997 Land Rover Discovery 1 that I purchased as my first Rover. It has generally ran pretty well aside from problems starting and staying running. Usually stepping on the gas and keeping the RPMs up for a minute or 2 solve the problem. Only code on OBD II reader is P0116. I have changed all the fluids and seafoamed it. I has new plugs and wires.

I decided to change out the thermostat and when I pulled it, only the rim of the thermostat was there. No spring or barrier. I went ahead and installed a new thermostat. Now when I add coolant, I get a massive leak from behind the engine that drains all the coolant within an hour or so. I have noticed pooled coolant around the two front manifold screws and pooled on the gasket in the rear after the leak.

I am in the process of pulling the intake manifold with the intent of checking for leaks and replacing the gasket. Any other thoughts as to what might be going on? The change with the installation of a thermostat is kinda throwing me....
 

Friday Night Disco

Well-known member
Jan 14, 2018
60
7
Fall City
The pressure from the bleeding process may have caused an old hose to finally let go. I would check the TBH hose and the metal pipe that goes into the header on the right hand side. Both of these will pool in the valley gasket and leak out the back of the engine
 

lfoster

Member
Apr 5, 2020
7
0
New Mexico
I am trying to make sure I understand all the possible locations this leak could be coming from. Do I need to remove the intake manifold?
 

StangGT5

Well-known member
Feb 4, 2019
295
130
Atlanta, GA
If you did not seal the thermostat correctly (might have shifted on install) or left the radiator hose a little lose, both of those would cause pooling in the intake which could run to the back of the engine. If you're seeing pooling on bolts and leaking at the back of the engine, the manifold gasket/valley gasket may have let go.
 

WaltNYC

Well-known member
Mar 3, 2010
707
135
NYC
I suspect pictures of the top end, and particularly around the t-stat housing, would go a long way in this case.
 

pdxrovermech

Well-known member
Jul 3, 2009
1,807
57
Portland, OR
TBH hoses were not really an issue with D1s. The 2in long heater pipe hose to the manifold is a common failure. Also its pretty easy to get the thermostat and gasket misaligned when bolting back together. The rad hose clamp on there can be an issue too. Put a wrench on your manifold bolts and see if they are loose.
 

lfoster

Member
Apr 5, 2020
7
0
New Mexico
So I am attaching a couple of pics. There was never a puddle underneath the TBH hoses or the Thermostat housing. There was some coolant in the depression of the 2nd right and left manifold bolts and on the gasket valley in the rear. I am in the process of removing the manifold. I did notice that when I loosened the fourth bolt on the passenger side, suddenly a significant amount of coolant drained out the rear again. I am attaching some pics that show the thermostat housing and where the coolant seems to have gathered. The coolant under the Thermostat housing has only just recently gathered there, but it does not seem to be coming from the housing.

Thanks again for everyones input.
 

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Icannap1

Well-known member
Mar 3, 2015
123
21
OC, CA
Picture 2 should have a fitting that is for cabin heater it is possible that the leak is coming from there due to the coloration on thee metal.
 

lfoster

Member
Apr 5, 2020
7
0
New Mexico
I removed it to get at the manifold screw. It was not the best looking, but I did not ever see a frank leak from there. And this leak was brisk. I lost nearly all my coolant within an hour.
 

Friday Night Disco

Well-known member
Jan 14, 2018
60
7
Fall City
IMO there are 3 ways for coolant to collect in the valley pan. You have ruled out the TBH so it is either a leak from that pipe and or one of the heater matrix hose or the head gasket (probably unlikely). I say this as I can not think of a way that coolant would get that high up in the engine bay.

I had a small leak on that pipe and I would go through a cup of coolant every couple of hours. If it is a bad leak in that area I could see how it would drain the engine of coolant.

Finally, fill the truck up with coolant, run the truck and look under the hood at the different locations that have been described. If the truck is leaking that much coolant you should be able to see the source
 

lfoster

Member
Apr 5, 2020
7
0
New Mexico
Thanks for the input. I kinda feel like I am "in it" now. I am pulling the intake manifold and going to clean it up and take a look. I kinda feel like at that point pulling the heads and checking them out and replacing the gasket is not a bridge to far.

I still don't quite understand why putting in a thermostat would have precipitated the leak. There must have been a reason the owners before me modified the thermostat. That has me pretty baffled.
 

Friday Night Disco

Well-known member
Jan 14, 2018
60
7
Fall City
Thanks for the input. I kinda feel like I am "in it" now. I am pulling the intake manifold and going to clean it up and take a look. I kinda feel like at that point pulling the heads and checking them out and replacing the gasket is not a bridge to far.

I still don't quite understand why putting in a thermostat would have precipitated the leak. There must have been a reason the owners before me modified the thermostat. That has me pretty baffled.

When you bleed the system, it will build up pressure greater than normal operations because of the air pockets. This over pressurization could have cause a weak link in the chain to finally go
 

lfoster

Member
Apr 5, 2020
7
0
New Mexico
So pulled valve covers and manifold and thought I would post some pics and see if anyone notices something with a trained eye that I wouldn't catch. I thought the heads actually looked pretty good.
 

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lfoster

Member
Apr 5, 2020
7
0
New Mexico
So an update on my coolant leak. It appears that after installing the thermostat, it is leaking beneath the manifold underneath this large screw (bypass?) I am assuming that it is coming from the screw hole and leaking underneath the manifold. Can I remove this screw and replace it? Any advice would be great.
 

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